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It seems an obvious course to avoid unnecessary risks buy cheap quetiapine medicine cabinet, but • Drugs may be highly selective for one pathway but the there is disagreement on what risks are truly unnecessary mechanism affected has widespread functions and and order quetiapine 200 mg overnight delivery symptoms to pregnancy, on looking closely at the matter order quetiapine online medications and grapefruit juice, it is plain that many interference with it cannot be limited to one site people habitually take risks in their daily and recreational only, e. Furthermore, some risks, although known to exist, • Prolonged modification of cellular mechanisms can lead are, in practice, ignored other than by conforming to to permanent change in structure and function, e. Risk has two elements: • Dosage adjustment according to need is often • The likelihood or probability of an adverse event. In such cases, when disaster Strategies that can limit risk include those directed at occurs, it can be difficult indeed for individuals to accept achieving: that they ‘deliberately’ accepted a risk; they feel ‘it should • Better knowledge of disease (research) – as much as 40% of not have happened to me’ and in their distress they may useful medical advances derive from basic research that seek to lay blame on others where there is no fault or neg- was not funded towards a specific practical outcome. The benefits of chemicals used to colour food verge on or • Site-specific delivery – drug targeting: even attain negligibility, although some cause allergy in n by topical (local) application humans. Such risks include transport and ease is life-threatening and there is reliable information on sports, both of which are inescapably subject to potent both the disease and the drug, then decisions, though they physical laws such as gravity and momentum, and may be painful, present relatively obvious problems. It is also unreasonable to expect the public to trust nience rather than for need, then the issues of risk the medical profession (in collaboration with the pharma- acceptance are less obvious. The risk comprises the properties of the drug, the pre- Patients are aware that there is justifiable criticism of the scriber, the patient and the environment; it is often so standards of medical prescribing – indeed doctors are in the small that second thoughts are hardly necessary, but forefront of this – as well as justifiable criticism of promo- sometimes it is substantial. The doctor must weigh the tional practices of the profitably rich, aggressive, transna- likelihood of gain for the patient against the likelihood tional pharmaceutical industry. There are often insufficient data for a rational de- There are obvious areas where some remedial action is cision to be reached, but a decision must yet be made, and possible: this is one of the greatest difficulties of clinical practice. Its • Improvement of prescribing by doctors, including better effect on the attitudes of doctors is often not appreciated communication with patients, i. The pa- to feel that introduction of foreign chemicals into their tient’s protection lies in the doctor’s knowledge of the patients’ bodies is a serious matter, which many or drug and of the disease, and experience of both, together 14 most do not seem to feel at present. This can be very difficult for the patient who medical profession, industrial drug developers, has suffered a rare severe adverse reaction to understand politicians and other ‘opinion-formers’ in society, and and to accept (see below). In some chronic diseases that ultimately necessitate • Restraint in promotion by the pharmaceutical industry suppressive drugs, the patient may not experience benefit including self-control by both industry and doctors in the early stages. Patients with early Parkinson’s disease in their necessarily close relationship, which the may experience little inconvenience or hazard from the public is inclined to regard as a conspiracy, especially condition, and premature exposure to drugs can exact such when the gifts and payments made to doctors get into a price in unwanted effects that they prefer the untreated thenews. If restraint by both parties is not forthcoming, and it may not be, then both doctor and industry can expect even more control to be exercised over them by politicians responding to public demand. It is unjustified to assert that a treatment is worthless just because its mention on death certificates (whether as a prime or as a contributory Extremist critics have attracted public attention for their cause) has not declined. The relevant criteria for view that modern drug therapy, indeed modern medicine juvenile-onset diabetes are change in the age at which in general, does more harm than good; others, while the subjects die and the quality of life between diagnosis admitting some benefits from drugs, insist that this is med- and death, and both of these have changed enormously. Overall mortality figures are an extremely Negligence and strict and no-fault crude and often an irrelevant measure of the effects of drugs liability whose major benefits are so often on quality of life rather than on its quantity. All civilised legal systems provide for compensation to be Two examplesofinappropriate measurementswillsuffice: paid to a person injured as a result of using a product of 1. In the case of many infections it is not disputed any kind that is defective due to negligence (fault: failure to exercise reasonable care). But this does not mean injury, beyond the modest sums that general social secu- that environmental improvements alone are rity systems provide, should be automatic and not depen- sufficient in the fight against infections. Environmentalchangesachievedtheirresultswhen (compensation) regardless of the cause of injury and mortality from infections was high and antimicrobials whether or not the producer and, in the case of drugs, werenotavailable;antimicrobials wereintroduced later the prescriber deserves censure. The question why a per- against a background of low mortality as well as of son who has suffered injury due to the biological accident environmentalchange;decadesseparatethetwopartsof of disease should have to depend on social security pay- the comparison, and observers, diagnostic criteria and ments while an identical injury due to a drug (in the ab- data recording changed during this long period. It is sence of fault) should attract special added compensation evident that determining the value of antimicrobials is receives no persuasive answer except that this is what so- not simply a matter of looking at mortality rates. This is no surprise experience as a remedy capable of limiting the progress of the 15 disease’, wrote the great Sir William Osler, successively Professor of because all must die and insulin is no cure for this Medicine in Pennsylvania, McGill, Johns Hopkins and Oxford lifelong disease. A standard medical textbook of 1907 universities, in 1918, only 3 years before the discovery of insulin. A manufacturing defect would companies as uninsurable lives: life seems to hang by a be dealt with in a way no different from manufacturing errors in other thread, a thread often cut by a very trifling accident’. Most, if not all, life insurance companies now accept 18A plaintiff (person who believes he/she has been injured) seeking to young people with diabetes with no or only modest obtain compensation from a defendant (via the law of negligence) must prove three things: (1) that the defendant owed a duty of care to financial penalty, the premium of a person 5–10 years the plaintiff; (2) that the defendant failed to exercise reasonable care; older. Before insulin replacement therapy was available and (3) that the plaintiff has a suffered actual injury as a result. Strict liability: compensation is provided by the producer/ 15A cure eliminates a disease and may be withdrawn when this is manufacturer. This body Issues that are central to the debate include: would have authority to reimburse itself from others – • Capacity to cause harm is inherent in drugs in a manufacturer, supplier, prescriber – wherever that was way that sets them apart from other manufactured appropriate. Patients would be expect, and adverse effects that should be accepted compensated where: n causation was proven on ‘balance of probability’22 without complaint, must often be a matter of opinion and will vary with the disease being treated, e. It is appro- ‘defective’ so as to attract liability, is a highly complex priate, therefore, to discuss such medical systems here. It is the task of science to find the gems and to small numbers of subjects (healthy or patient discard the dross,24 and at the same time to leave intact so- volunteers): the developer should be strictly liable cially valuable supportive aspects of traditional medicine. Although the Commission medicine is not accessibleto large populationsfor economic reasons,and considered compensation for death and personal injury suffered by any destruction of traditional medicine would leave unhappy and sick people person through manufacture, supply or use of products, i. For this reason, governments are supporting traditional whether natural or manufactured, and included drugs and even medicine and at the same time initiating scientific clinical evaluations human blood and organs, it made no mention of tobacco and alcohol. It is difficult to resist the con- with any possible or even conceivable event (evidence) is clusion that when scientific medicine neither guarantees outside science, and this in general applies to cults where happiness nor wholly eliminates the disabilities of degen- everything is interpreted in terms of the theory of the cult; erative diseases in long-lived populations, and when drugs the possibility that the basis of the cult is false is not enter- used in modern medicine cause serious harm, public disap- tained. This appears to be the case with medical cults, pointment naturally leads to a revival of interest in alterna- which join freudianism, and indeed religions, as outside tives that alluringly promise efficacy with complete safety. Willingness to follow where These range from a revival of traditional medicine to adop- the evidence leads is a distinctive feature of conventional tion of the more modern cults. Features common to medical cults are: absence of scien- tific thinking, naive acceptance of hypotheses, uncritical ac- ceptance of causation, e. It does not mean the follows treatment it is due to the treatment, and close atten- exclusion of spiritual, psychological and social tion to the patient’s personal feelings. But it does mean treating ing of how therapeutic effects may be measured is also a these in a rational manner. Traditional (pre- 25 scientific) medicine is deemed to have special virtue, and Ernst E 2000 The role of complementary and alternative medicine. Thereisalso a tenet thatifthe patientgets betterwhen treated 27A cult is a practice that follows a dogma, tenet or principle based on theories or beliefs of its promulgator to the exclusion of demonstrable 28 scientific experience (definition of the American Medical Association). Ernst E (ed) 2001 The Desktop Guide to Complementary and Scientific medicine changes in accord with evidence obtained by Alternative Medicine. But this is not the case with cults, the claims for which are menopausal symptoms (but no better than placebo in clinical trial), can characterised by absence of rigorous intellectual evaluation and cause serious liver disorder. The profusion of medical cults prompts the (Senecio, Crotalaria, Heliotropium) cause serious hepatic veno-occlusive question why, if each cult has the efficacy claimed by its exponents, disease. Comfrey (Symphytum) is similar but also causes hepatocellular conventional medicine and indeed the other cults are not swept away.
Individuals The simplest form of an antigenic determinant order quetiapine overnight delivery medications 101, on a complex antigenic molecule quality 300mg quetiapine medicine cabinets recessed, that can combine with antibody or T-cell receptor (Stedman’s can change aspects of their lifestyle significantly to influ- Medical Dictionary) purchase quetiapine with amex medicine zebra. The connection between environment option for the population as a whole, or for groups at high and cancer risk is complex and as yet poorly understood, risk of a specific cancer. Retrospective epidemiological and as genetic susceptibilities may obviate or accentuate association studies suggest large effects of certain dietary certain risks. The • Organ or tissue transplantation: to prevent immune best example is supplemental vitamins, derivatives and di- rejection. But supplementation with ascorbic acid, vitamin E, b-carotene, they are generally too toxic for the above purposes and selenium and zinc over 7. Tamoxifen and anastrozole (see above) are under- With the exception of ciclosporin and tacrolimus, all of the going assessment for chemoprevention in women at high above cause non-specific immunosuppression, so that the risk of breast cancer. Cyclo- phosphamide is a second choice; it depresses bone marrow, In cancers thought to have predominantly viral origins as is to be expected. Ciclosporin is about 40% absorbed from the gastrointestinal tract and is metabolised exten- sively in the liver, mainly by the cytochrome P450 3A sys- Immunosuppression tem (t½ 27 h). Ciclosporin is used to prevent and treat rejection of Suppression of immune responses mediated via mononu- organ transplants (kidney, liver, heart–lung) and bone mar- clear cells (lymphocytes, plasma cells) is used in therapy of: row transplants. For organ transplants, treatment continues indefinitely and requires careful monitoring of plasma con- • Autoimmune, collagen, connective tissue and centration and renal function. In patients who have received inflammatory disorders including systemic lupus a bone marrow transplant, ciclosporin is generally stopped erythematosus, rheumatoid arthritis, chronic active after 6 months unless there is ongoing chronic graft- hepatitis, inflammatory bowel disease, versus-host disease. Ciclosporin constricts the pre- glomerular afferent arteriole and reduces glomerular filtra- 14 tion; acute or chronic renal impairment may result if the Hercberg S, Galan P, Preziosi P et al 2004 Randomized, placebo- controlled trial of the health effects of antioxidant vitamins and trough plasma concentration consistently exceeds minerals. Generally, renal changes resolve when the drug 523 Section | 6 | Blood and neoplastic disease is withdrawn. Hypertension develops in about 50% of pa- Mycophenolate tients, more commonly when a corticosteroid is co- Mycophenolate selectively blocks the proliferation of T and administered but possibly due in part to the mineralocor- B lymphocytes and acts like azathioprine; it is being evalu- ticoid action of ciclosporin. The blood pressure is con- ated in combination immunosuppressive regimens for or- trolled by standard antihypertensive therapy without the gan transplantation. Other adverse effects in- clude gastrointestinal reactions, hepatotoxicity, hyperka- laemia, hypertrichosis, gingival hypertrophy, convulsions Hazards of immunosuppressive drugs and, rarely, the clinical syndrome of thrombotic thrombo- cytopenic purpura. The plasma concentration of ciclosporin, tion early and vigorously (using bactericidal drugs where and risk of toxicity, is increased by drugs including ketoco- practicable); use human g-globulin to protect when there nazole, erythromycin, chloroquine, cimetidine, oral con- is exposure to virus infections, e. Grapefruit juice also increases plasma ciclos- therapeutic (as opposed to replacement) doses of cortico- porin concentrations (flavinoids in the juice inhibit the steroid are at risk of severe chickenpox; they should cytochrome that metabolises ciclosporin). Drugs that receive varicella zoster immunoglobulin if there has been reduce the plasma concentration of ciclosporin, risking loss contact with the disease within the previous 3 months and of effect, include enzyme-inducing antiepileptics, e. Hazards include those of long- Tacrolimus is a macrolide immunosuppressant agent that is term corticosteroid therapy, and of cytotoxics in general isolated from a bacterium. Such rescue treatment who has life-endangering disease, there is more cause for may be graft- orlife-saving. Tacrolimus can cause nephrotox- concern when immunosuppressive regimens are an option icity, neurotoxicity, disturbance of glucose metabolism, in younger patients with a less serious disorder, e. It is also used to treat severe aplastic Response to non-living antigens (tetanus, typhoid, polio- anaemia, frequently producing a good partial response ei- myelitis) is diminished, and giving one or two extra doses ther as a single agent or in combination with ciclosporin. The integrity population in Western societies experiences regular dys- of the sphincter can be compromised by the presence of pepsia, although the majority self-medicate with over- a hiatus hernia, which disrupts its anatomical and physio- the-counter anti-acid preparations and do not seek medical logical components. The remainder, in whom no abnormality oesophageal ulceration, stricturing resulting in mechanical is found, are diagnosed as having non-ulcer dyspepsia. Reduced oesophageal clearance of acid tions with a number of causes and, fortunately, a number may also contribute. A high sphincter tone and uncoordi- nated oesophageal contractions can cause dysphagia and The normal oesophagus effortlessly transfers food and pain. Intrinsic tonic results from an imbalance between these two opposing 528 Oesophagus, stomach and duodenum Chapter | 32 | forces. Other digestive enzymes such ous lifestyle factors adversely affect the mucosal barrier, as pepsinogen/pepsin also contribute to the gastric phase of including smoking and alcohol. Gastric or du- Locally produced prostaglandins E2 and I2 inhibit parietal odenal ulcers occur in 1–5%. Prostaglandins are produced by the sharply with age in those over 60 years, and the risk of ul- cyclo-oxygenase enzyme. Mucosal protective mechanisms (Marshall deliberately infected himself by drinking a solution swimming with the bacterium, as part of a successful and widely reported Mucus and bicarbonate is secreted by cells in the gastric and experiment to prove Koch’s postulates. Here the neutral intracellular pH causes the Other pharmacological targets which are showing potential drugs to become ionised and trapped in the mucosa be- in early clinical research include cannabinoid agonists. As can be deduced from the above, the beneficial anti-inflammatory effect is offset by the potential most effective site of action for antisecretory drugs is the for mucosal injury by depletion of protective prostaglan- proton pump. Although an increased the volume of acid available to reflux up the oesophagus, incidence of osteoporotic fractures and Clostridium difficile and secondly by increasing lower oesophageal sphincter (C. All are similar in trates, theophyllines, drugs with antimuscarinic activity or pharmacokinetics, efficacy and adverse effect profile. The phar- macology and pharmocokinetics of these drugs appear in Protective Aggressive detail elsewhere (see Index). These agents may occasionally be useful in alleviating the symptoms of oesophageal Prostaglandins Acid spasm, although the effect is usually disappointing. Commonly used examples include nifedipine, diltiazem, Mucosal blood flow Helicobacter pylori and modified-release nitrates. They competitively inhibit histamine binding at sium trisilicate more slowly with gastric hydrochloric acid. H2 receptors on the basolateral aspect of parietal cells, All magnesium salts cause an osmotic diarrhoea. The inhib- Aluminium hydroxide reacts with hydrochloric acid to itory effect can be overcome with high gastrin levels, as oc- form aluminium chloride; this in turn reacts with intestinal curs postprandially. Since there is anecdotal evidence be readily apparent from the name of the preparation that peptic ulcer healing with H2-receptor antagonists cor- and thus may be dangerous for patients with cardiac, renal relates best with suppression of nocturnal acid secretion, or liver disease. For example, a 10-mL dose of magnesium many prefer to give these drugs as a single evening dose carbonate mixture or of magnesium trisilicate mixture con- (e. Adverse effects and interactions are few with Aluminium- and magnesium-containing antacids may in- short-term use. Cimetidine is a weak anti-androgen, and terfere with the absorption of other drugs by binding with may cause gynaecomastia and sexual dysfunction in males. It is Cimetidine inhibits cytochromes P450 and there is poten- probably advisable not to co-administer antacids with tial for increased effect from any drug with a low thera- drugs that are intended for systemic effect by the oral route. A potential danger is that patients with serious ments for peptic ulceration are obsolete, but underlie the pathology such as gastric carcinoma will self-medicate, rationale for the surgical vagotomy which is now rarely allowing their disease to progress. They protect the gastric mucosa against acid (by hydroxide complex) neutralisation) and pepsin (which is inactive above pH 5, and which in addition is inactivated by aluminium Sucralfate provides a physical barrier to gastric acid. Most commonly they are magnesium or tivated by acid to produce a viscous gel, and will therefore aluminium salts. The hydroxide is the most common base, be ineffective if given with therapies that inhibit acid release but trisilicate, carbonate and bicarbonate are also used.
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The risk is essentially zero at serum urate con- the possibility of the formation of uric acid stones buy generic quetiapine 100 mg on-line medications with weight loss side effect. If a The binding of uric acid to plasma proteins is relatively patient on a purine-restricted diet for 1 week excretes small and probably does not have great physiological more than 600 mg uric acid per 24 hours purchase genuine quetiapine on-line treatment quadriceps tendonitis, the individual signiﬁcance purchase quetiapine 200 mg line medications during labor. If, however, less than 350 affected by administration of drugs, such as salicylates, mg of uric acid is eliminated in 24 hours, suspect im- phenylbutazone, probenecid, and sulﬁnpyrazone. Urate is gouty arthritic problems have nonetheless been found believed to be transported from the ultraﬁltrate to the to have uric acid deposited on their articular cartilage. This active transport system can be inhib- crystals is accompanied by cellular release of chemotac- ited by drugs, such as probenecid, sulﬁnpyrazone, and tic lipids, lysosomal enzymes, and acidic substances into salicylate. The lipids appear to trigger further sively across the basolateral membrane and into the phagocytosis, whereas the acidic compounds decrease peritubular ﬂuid down its electrochemical gradient. The urate cytes, small peptide substances, such as the kinins, which accumulated in the cell moves passively across the lu- are thought to be partially responsible for the local in- minal membrane into the ultraﬁltrate along its concen- ﬂammatory response in gouty arthritis, accumulate in tration gradient. The inﬂammation is associated with lo- can be inhibited by a variety of organic anions, includ- cal vasodilation, increased vascular permeability, and ing the thiazide and loop diuretics. The intracellular concentration of urate in the proxi- mal tubule will ultimately be determined by the balance of inﬂux and efﬂux. In contrast, when Initial treatment of gout and its associated hyper- the transport of urate from luminal ﬂuid is high, there is uricemia must involve therapy directed toward termi- a net reabsorption across the basolateral membrane. A variety of ety of organic anions, including uricosuric agents, nonsteroidal antiinﬂammatory compounds (e. It is these released substances that are re- sulindac) can be administered either alone or in combi- sponsible for much of the local inﬂammation and pain nation with colchicine, a relatively speciﬁc agent for use associated with acute attacks of gout. Glucocorticosteroids, such as Colchicine, an alkaloid obtained from the autumn prednisone, can be given as a tapered dose over 10 days crocus, has long been used and is relatively selective for to replace colchicine. If the diagnosis is uncertain, the newer agents for use in gout, colchicine has minimal colchicine should be used, since a response to this drug effects on uric acid synthesis and excretion; it decreases is generally taken as establishing the diagnosis of acute inﬂammation associated with this disorder. The lopurinol, probenecid, or sulﬁnpyrazone during an ability of colchicine to bind to leukocyte microtubules acute attack, since the therapy itself, at least during the in a reversible covalent complex and cause their de- initial stages, may exacerbate the condition. Once the polymerization also may be a factor in decreasing the acute symptoms are under control and the patient is attraction of the motile leukocytes into the inﬂamed asymptomatic, appropriate treatment should include area. Long-term tion and tends to concentrate in the spleen, kidney, treatment is directed toward decreasing uric acid produc- liver, and gastrointestinal tract. Since colchicine can accumulate in drug therapy than by dietary restriction, because only a cells against a concentration gradient, it is postulated small portion of blood uric acid is derived from the di- that an active transport process may be involved in its etary intake of purines. The drug is metabolized, primarily in creased by increasing the rate of urine ﬂow or by using the liver, by deacetylation. Since uric acid is ﬁltered at the role in colchicine elimination, since it and its metabo- glomerulus and both actively secreted and reabsorbed by lites are readily secreted into the bile. Since colchicine is so rap- glance the use of a combination of drugs—a drug that idly effective in relieving the acute symptoms of gout reduces production along with one that is uricosuric— (substantial improvement is achieved within hours), it would seem to be a rational therapeutic approach, in has been used as a diagnostic aid in this disorder. Apparently the effec- Therapy with colchicine is usually begun at the ﬁrst tiveness of a drug that inhibits uric acid synthesis can be sign of an attack and is continued until symptoms sub- diminished by uricosuric agents, and therefore the com- side, adverse gastrointestinal reactions appear, or a bination has less value than each drug used separately. The drug Furthermore, side effects appear to occur more fre- can be given intravenously as well as orally, but care quently during combination drug therapy. It should be used with caution with local accumulation of urate microcrystals by the in patients with preexisting compromised heart, kidney, phagocytic neutrophils. Uric acid may be actively reabsorbed from the ultraﬁltrate following its glomerular ﬁltration or it may be secreted from the blood across the basolateral membrane into the proximal tubular cell. The hepatobiliary recy- mechanism is relatively minor, however, and at high cling of colchicine and its antimitotic effect on cells that dosages these same drugs increase uric acid elimination are rapidly turning over, such as those of the intestinal by inhibiting its proximal tubular reabsorption. Therefore, it is wise to begin ther- are somewhat similar to urate in structure; therefore, apy with the administration of small amounts of they can compete with uric acid for transport sites. In addition, the initial rise in urinary uric the total excretion of urate by inhibiting its tubular se- acid concentrations during uricosuric drug therapy may cretion. In contrast, low dosages of probenecid appear to com- Sulﬁnpyrazone is readily absorbed after oral admin- pete preferentially with plasma uric acid for the proxi- istration, with peak blood levels reached 1 to 2 hours af- mal tubule anionic transport system and thereby block ter ingestion. The uricosuric (98–99%) than is probenecid (84–94%) and is a more action of probenecid, however, is accounted for by the potent uricosuric agent. Most of the drug (90%) is elim- drug’s ability to inhibit the active reabsorption of ﬁl- inated through active proximal tubular secretion of the tered urate. Sulﬁnpyrazone also undergoes Probenecid is rapidly absorbed after oral administra- p-hydroxylation to form a uricosuric metabolite, the tion, with peak plasma levels usually reached in 2 to 4 formation of which undoubtedly contributes to the hours. Its half-life is somewhat variable (6–12 hours) be- drug’s prolonged activity (about 10 hours) and potency cause of both its extensive plasma protein binding and relative to probenecid. Since tubular back- rate of excretion of sulﬁnpyrazone is not enhanced by diffusion is decreased at alkaline urinary pH ranges, alkalinization of the urine, since the drug is largely ion- probenecid excretion increases with increasing urinary ized at all urinary pH ranges and therefore not a candi- pH. It is not useful in treating acute at- Abdominal pain, nausea, and possible reactivation tacks of gouty arthritis. The drug should be excreted is greater than 800 mg/day, the urine should be used with caution in patients with compromised renal alkalinized to prevent kidney stone formation and pro- function, and adequate ﬂuid intake should always ac- mote uric acid. If these agents are to be given con- comitantly with probenecid, their dosage should be mod- Allopurinol (Zyloprim) is the drug of choice in the treat- iﬁed appropriately. Salicylates interfere with the clinical ment of chronic tophaceous gout and is especially useful effects of both sulﬁnpyrazone and probenecid and should in patients whose treatment is complicated by renal in- be avoided in patients treated with uricosuric agents. Uricosuric agents also can inﬂuence the volume of distri- bution and hepatic metabolism of a number of drugs. Mechanism of Action Adverse reactions associated with probenecid ther- Allopurinol, in contrast to the uricosuric drugs, reduces apy include occasional rashes, allergic dermatitis, upper serum urate levels through a competitive inhibition of gastrointestinal tract irritation, and drowsiness. The uric acid synthesis rather than by impairing renal urate drug is contraindicated in patients with a history of re- reabsorption. After enzyme inhibition, the urinary and blood concentra- Sulﬁnpyrazone tions of uric acid are greatly reduced and there is a si- Sulﬁnpyrazone (Anturane), another uricosuric agent, is multaneous increase in the excretion of the more solu- chemically related to the antiinﬂammatory and urico- ble uric acid precursors, xanthine and hypoxanthine. This phenomenon contributes to the thera- drugs also metabolized by this system should be done peutic effectiveness of allopurinol in long-term use. Because allopurinol inhibits the oxidation Oxypurinol is probably responsible for the antigout ef- of mercaptopurine and azathioprine, their individual fects of allopurinol. Oxypurinol itself is not adminis- administered doses must be decreased by as much as tered because it is not well absorbed orally. Allopurinol may also increase the toxicity of other cy- Absorption, Metabolism, and Excretion totoxic drugs (e. The actions of allopuri- Allopurinol is largely absorbed after oral ingestion, nol are not antagonized by the coadministration of sal- reaching peak blood levels in about 1 hour. Clinical Uses Indomethacin (Indocin) (see Chapter 36) exerts an- Allopurinol is especially indicated in the treatment of tiinﬂammatory, antipyretic, and analgesic properties. Its nisms for its efﬁcacy, allopurinol is particularly beneﬁcial antiinﬂammatory activity and ability to inhibit leuko- for patients who already have developed renal uric acid cytic phagocytosis make it particularly valuable in treat- stones, patients with excessively high urate excretion ing the early stages of gout, because a decrease in the (e.
These agents should be used with caution and in reduced dosage in patients with hepatic parenchymal disease discount quetiapine 50mg line medicine evolution, north Asians cheap quetiapine 100mg on-line medicine keflex, and the elderly quetiapine 50 mg visa medicine 5 rights. In general, aminotransferase activity should be measured at baseline, at 1–2 months, and then every 6–12 months (if stable). Monitoring of liver enzymes should be more frequent if the patient is taking other drugs that have potential interactions with the statin. Long-term studies have shown a small but significant increase in the incidence of type 2 diabetes in statin-treated patients, most of whom had findings of prediabetes before treatment. Myopathy may occur with monotherapy, but there is an increased incidence in patients also receiving certain other drugs. The 3A4-dependent reductase inhibitors tend to accumulate in plasma in the presence of drugs that inhibit or compete for the 3A4 cytochrome. Concomitant use of reductase inhibitors with amiodarone or verapamil also causes an increased risk of myopathy. Pravastatin and rosuvastatin appear to be the statins of choice for use with verapamil, the ketoconazole group of antifungal agents, macrolides, and cyclosporine. Plasma levels of lovastatin, simvastatin, and atorvastatin may be elevated in patients ingesting more than 1 liter of grapefruit juice daily. Creatine kinase activity should be measured in patients receiving potentially interacting drug combinations. Rarely, hypersensitivity syndromes have been reported that include a lupus-like disorder and peripheral neuropathy. Reductase inhibitors may be temporarily discontinued in the event of serious illness, trauma, or major surgery to minimize the potential for liver and muscle toxicity. Use of red yeast rice, a fermentation product that contains statin activity, is not recommended because the statin content is highly variable and some preparations contain a nephrotoxin, citrinin. The long-term safety of these preparations, which often contain a large number of poorly studied organic compounds, has not been established. Chemistry & Pharmacokinetics Gemfibrozil is absorbed quantitatively from the intestine and is tightly bound to plasma proteins. These effects are mediated by activation of peroxisome proliferator-activated receptor-α, which modulates the expression of several proteins. They also may be of benefit in treating the hypertriglyceridemia that results from treatment with antiviral protease inhibitors. The dosage of fenofibrate (as Tricor) is one to three 48 mg tablets (or a single 145 mg tablet) daily. Toxicity Rare adverse effects of fibrates include rashes, gastrointestinal symptoms, myopathy, arrhythmias, hypokalemia, and high blood levels of aminotransferases or alkaline phosphatase. Both agents potentiate the action of coumarin and indanedione anticoagulants, and doses of these agents should be adjusted. There appears to be a modest increase in the risk of cholesterol gallstones, reflecting an increase in the cholesterol content of bile. Therefore, fibrates should be used with caution in patients with biliary tract disease or in those at higher risk such as women, obese patients, and Native Americans. Historically, combination therapy including niacin has been associated with regression of atherosclerotic coronary lesions in three angiographic trials and with extension of life span in one large trial in which patients received niacin alone. No significant reduction of major vascular events was observed in the niacin/laropiprant group vs the group that took the statin alone, but the risk of adverse events was increased. It is likely that niacin offers therapeutic benefit for such patients and those with statin intolerance. One, N-methyl nicotinamide, creates a draft on methyl groups that can occasionally result in erythrocyte macrocytosis, similar to deficiency of folate or vitamin B12. Excretion of neutral sterols in the stool is increased acutely as cholesterol is mobilized from tissue pools and a new steady state is reached. In severe mixed lipemia that is incompletely responsive to diet, niacin often produces marked reduction of triglycerides, an effect enhanced by marine omega-3 fatty acids. For treatment of heterozygous familial hypercholesterolemia, most patients require 2–6 g of niacin daily; more than this should not be given. Crystalline niacin should be given in divided doses with meals, starting with 100 mg two or three times daily and increasing gradually. Toxicity Most persons experience a harmless cutaneous vasodilation and sensation of warmth after each dose when niacin is started or the dose increased. Many can continue the drug at reduced dosage, with inhibitors of gastric acid secretion or with antacids not containing aluminum. Reversible elevations in aminotransferases up to twice normal may occur, usually not associated with liver toxicity. The association of severe hepatic dysfunction, including acute necrosis, with the use of over-the-counter sustained-release preparations of niacin has been reported. This effect has not been noted to date with an extended-release preparation, Niaspan, given at bedtime in doses of 2 g or less. Carbohydrate tolerance may be moderately impaired, especially in obese patients, but this is usually reversible except in some patients with latent diabetes. Niacin may be given to diabetics who are receiving insulin and to some receiving oral agents but it may increase insulin resistance. Chemistry & Pharmacokinetics The bile acid-binding agents are large polymeric cationic exchange resins that are insoluble in water. Mechanism of Action Bile acids, metabolites of cholesterol, are normally efficiently reabsorbed in the jejunum and ileum (Figure 35–2). Excretion is increased up to tenfold when resins are given, resulting in enhanced conversion of cholesterol to bile acids in liver via 7α-hydroxylation, which is normally controlled by negative feedback by bile acids. The latter effect is due to increased secretion of the incretin glucagon-like peptide-1 from the intestine, thus increasing insulin secretion. Therefore, the resins are without effect in patients with homozygous familial hypercholesterolemia who have no functioning receptors but may be useful in those with some residual receptor function and in patients with receptor-defective combined heterozygous states. Resins are also used in combination with other drugs to achieve further hypocholesterolemic effect (see below). They may be helpful in relieving pruritus in patients who have cholestasis and bile salt accumulation. Colestipol is also available in 1 g tablets that must be swallowed whole, with a maximum dose of 16 g daily. Toxicity Common complaints are constipation and bloating, usually relieved by increasing dietary fiber. Increased formation of gallstones, particularly in obese persons, was an anticipated adverse effect but has rarely occurred in practice. Absorption of certain drugs, including those with neutral or cationic charge as well as anions, may be impaired by the resins. These include digitalis glycosides, thiazides, warfarin, tetracycline, thyroxine, iron salts, pravastatin, fluvastatin, ezetimibe, folic acid, phenylbutazone, aspirin, and ascorbic acid, among others. In general, additional medication (except niacin) should be given 1 hour before or at least 2 hours after the resin to ensure adequate absorption.