Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sildenafil, a selective inhibitor of phosphodiesterase type 5 (PDE5), is the first in a new class of orally effective treatments for erectile dysfunction. During sexual stimulation, the cavernous nerves release nitric oxide (NO), which induces cyclic guanosine monophosphate (cGMP) formation and smooth muscle relaxation in the corpus cavernosum. Sildenafil facilitates the erectile process during sexual stimulation by inhibiting PDE5 and thus blocking the breakdown of cGMP. Sildenafil alone can cause mean peak reductions in systolic/diastolic blood pressure of 10/7 mm Hg that are not dose related, whereas the heart rate is unchanged. Sildenafil and nitrates both increase cGMP levels in the systemic circulation but at different points along the NO-cGMP pathway. The combination is contraindicated because they synergistically potentiate vasodilation and may cause excessive reductions in blood pressure. Erectile dysfunction is a significant medical condition that shares numerous risk factors with ischemic heart disease, and hence a substantial overlap exists between these patient groups. From extensive clinical trials, the most commonly reported cardiovascular adverse events in patients treated with sildenafil were headache (16%), flushing (10%), and dizziness (2%). The incidences of hypotension, orthostatic hypotension, and syncope and the rate of discontinuation of treatment due to adverse events were <2% and were the same in patients taking sildenafil and those taking placebo. Retrospective analysis of the concomitant use of antihypertensive medications (beta blockers, alpha blockers, diuretics, angiotensin-converting enzyme inhibitors, and calcium antagonists) in patients taking sildenafil did not indicate an increase in the reports of adverse events or significant episodes of hypotension compared with patients treated with sildenafil alone. In clinical trials, the incidence of serious cardiovascular adverse events, including stroke and myocardial infarction, was the same for patients treated with sildenafil or placebo. Concurrent disease states, such as renal or hepatic impairment, or concomitant use of inhibitors of the cytochrome P450 isozyme CYP3A4 could increase systemic exposure to sildenafil. Since the US market launch in April 1998, monitoring of spontaneous adverse event reports in association with sildenafil has demonstrated a pattern that is generally consistent with the experience observed during clinical development, with the exception of infrequent reports of priapism. In conclusion, extensive clinical testing has shown that overall treatment with sildenafil for up to 1 year is well tolerated and is associated with a low incidence of adverse events that result in discontinuation of treatment in <3% of patients.
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PMID:Overall cardiovascular profile of sildenafil citrate. 1007 41

The HMG-CoA reductase inhibitors (statins) are effective in both the primary and secondary prevention of ischaemic heart disease. As a group, these drugs are well tolerated apart from two uncommon but potentially serious adverse effects: elevation of liver enzymes and skeletal muscle abnormalities, which range from benign myalgias to life-threatening rhabdomyolysis. Adverse effects with statins are frequently associated with drug interactions because of their long-term use in older patients who are likely to be exposed to polypharmacy. The recent withdrawal of cerivastatin as a result of deaths from rhabdomyolysis illustrates the clinical importance of such interactions. Drug interactions involving the statins may have either a pharmacodynamic or pharmacokinetic basis, or both. As these drugs are highly extracted by the liver, displacement interactions are of limited importance. The cytochrome P450 (CYP) enzyme system plays an important part in the metabolism of the statins, leading to clinically relevant interactions with other agents, particularly cyclosporin, erythromycin, itraconazole, ketoconazole and HIV protease inhibitors, that are also metabolised by this enzyme system. An additional complicating feature is that individual statins are metabolised to differing degrees, in some cases producing active metabolites. The CYP3A family metabolises lovastatin, simvastatin, atorvastatin and cerivastatin, whereas CYP2C9 metabolises fluvastatin. Cerivastatin is also metabolised by CYP2C8. Pravastatin is not significantly metabolised by the CYP system. In addition, the statins are substrates for P-glycoprotein, a drug transporter present in the small intestine that may influence their oral bioavailability. In clinical practice, the risk of a serious interaction causing myopathy is enhanced when statin metabolism is markedly inhibited. Thus, rhabdomyolysis has occurred following the coadministration of cyclosporin, a potent CYP3A4 and P-glycoprotein inhibitor, and lovastatin. Itraconazole has been shown to increase exposure to simvastatin and its active metabolite by at least 10-fold. Pharmacodynamically, there is an increased risk of myopathy when statins are coprescribed with fibrates or nicotinic acid. This occurs relatively infrequently, but is particularly associated with the combination of cerivastatin and gemfibrozil. Statins may also alter the concentrations of other drugs, such as warfarin or digoxin, leading to alterations in effect or a requirement for clinical monitoring. Knowledge of the pharmacokinetic properties of the statins should allow the avoidance of the majority of drug interactions. If concurrent therapy with known inhibitors of statin metabolism is necessary, the patient should be monitored for signs and symptoms of myopathy or rhabdomyolysis and the statin should be discontinued if necessary.
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PMID:Pharmacokinetic-pharmacodynamic drug interactions with HMG-CoA reductase inhibitors. 1203 92

Bosentan is the first endothelin (ET) receptor antagonist approved by the Food and Drug Administration for the management of pulmonary arterial hypertension (PAH). In patients with World Health Organization Class III and IV PAH, bosentan has demonstrated improvement in dyspnea and exercise tolerance. ET also plays an important role in the pathophysiology of different vascular diseases. Therefore, bosentan also may have the potential to alter the outcome of many other diseases, such as heart failure, hypertension, ischemic heart disease, and renal disease, as well as cerebrovascular disorders. Because of the rarity and the poor prognosis of patients with PAH, as well as the requirement of close monitoring of bosentan (due to its potential of causing liver dysfunction and its teratogenic effects), bosentan is currently available only through a special access program and is distributed by certain selected pharmacies. Patients who are receiving bosentan should be taught to recognize early signs and symptoms of liver dysfunction and possible pregnancy. In addition, bosentan is not only a substrate but also an inducer of CYP3A4 and CYP2C9. Therefore, it is anticipated that numerous drug interactions may occur. Patients should be advised to consult their physicians or pharmacists should they need to consume other prescription or nonprescription medications.
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PMID:Bosentan. 1271 83

Recent studies suggest that cytochrome P450 (CYP) 3A4 metabolized statins attenuate the antiaggregatory effect of clopidogrel. We evaluated how CYP3A4 metabolized statins and non-CYP3A4 metabolized statins influence platelet aggregation when given concomitantly with clopidogrel. Sixty-six stable patients with ischemic heart disease were included in this parallel group study. All patients were on clopidogrel and aspirin. Thirty-three patients received a CYP3A4 metabolized statin (simvastatin or atorvastatin), and 33 were treated with a non-CYP3A4 metabolized statin (pravastatin). The antiplatelet effect of clopidogrel was assessed at inclusion and 21 days after statin discontinuation. Platelet function was evaluated by two methods 1) optical platelet aggregometry after stimulation with 20 and 30 microM ADP, and 2 and 4 mg/l collagen, respectively, 2) a Platelet FunctionAnalyzer-100. The primary effect measure was final platelet aggregation after stimulation with 20 microM ADP. No difference was observed between patients treated with a CYP3A4 metabolized statin and patients receiving a non-CYP3A4 metabolized statin (30% point (7-42) versus 20% point (9-32), p = 0.83). Platelet aggregation was not improved by discontinuation of statins for 21 days. Indeed, we found that statin treatment given concomitantly with clopidogrel resulted in an improved platelet inhibition when compared to clopidogrel given alone. The antiplatelet effect of clopidogrel is not attenuated by concomitant treatment with a CYP3A4 metabolized statin in patients with clinical stable ischemic heart disease.
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PMID:The antiplatelet effect of clopidogrel is not attenuated by statin treatment in stable patients with ischemic heart disease. 1611 10

Clopidogrel and statins are frequently administered in patients with ischemic heart disease or other atherothrombotic manifestations and are effective in the prevention of cardiovascular disease. The thienopyridine clopidogrel is a pro-drug metabolised in the liver via the cytochrome P450 (CYP) 3A4 system to the active compound which inhibits the P2Y(12) ADP platelet receptor. The assumption exists that the effect of clopidogrel in inhibiting platelet aggregation is attenuated by co-administration of lipophilic statins such as atorvastatin or simvastatin which are metabolised by the CYP3A4 system to inactive substrates. Assessing a possible drug-drug interaction ex-vivo, inconclusive studies have been published: In an aggregometer study, a strong and dose-dependent interference between atorvastatin and the inhibitory effect of clopidogrel on platelet function was observed. Another study, measuring the effect of clopidogrel by flow cytometry, found a significant attenuation of the clopidogrel effect by lipophilic statins, predominantly in the loading phase. In contrast a recent study, which used 600 mg clopidogrel for loading, found no significant interference between various statins and clopidogrel on ADP-induced platelet aggregation and in addition another study revealed no attenuation of the clopidogrel effect despite statin co-medication after 5 weeks. Additionally, retrospective analysis of clinical studies (CREDO-study) or registries (MITRA-PLUS) revealed no significant influence of different statins on the clinical outcome in patients treated with clopidogrel. However, these clinical studies showed a trend towards a diminishing effect of clopidogrel on those treated with cytochrome CYP3A4 metabolised statins. Even more important seems to be the considerable variability in the response of the antiplatelet effect of clopidogrel. A certain percentage of patients apparently do not respond adequately to clopidogrel treatment. This effect of clopidogrel resistance seems to be more important as the potential interference between CYP3A4 metabolized statins and clopidogrel. Finally, up until now sufficient evidence has not been gained to prefer hydrophil statins on patients receiving clopidogrel co-medication or when to discontinue the use of statins in clopidogrel treatment. Prospective studies are necessary in order to evaluate the magnitude of clopidogrel resistance and the impact of clopidogrel co-medication as well as to redefine antithrombotic therapy for this subgroup.
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PMID:Thienopyridines and statins: assessing a potential drug-drug interaction. 1661 Nov 11

Amlodipine is a commonly prescribed calcium channel blocker for the treatment of hypertension and ischemic heart disease. The drug is slowly cleared in humans primarily via dehydrogenation of its dihydropyridine moiety to a pyridine derivative (M9). Results from clinical drug-drug interaction studies suggest that CYP3A4/5 mediate metabolism of amlodipine. However, attempts to identify a role of CYP3A5 in amlodipine metabolism in humans based on its pharmacokinetic differences between CYP3A5 expressers and nonexpressers failed. Objectives of this study were to determine the metabolite profile of amlodipine (a racemic mixture and S-isomer) in human liver microsomes (HLM), and to identify the cytochrome P450 (P450) enzyme(s) involved in the M9 formation. Liquid chromatography/mass spectrometry analysis showed that amlodipine was mainly converted to M9 in HLM incubation. M9 underwent further O-demethylation, O-dealkylation, and oxidative deamination to various pyridine derivatives. This observation is consistent with amlodipine metabolism in humans. Incubations of amlodipine with HLM in the presence of selective P450 inhibitors showed that both ketoconazole (an inhibitor of CYP3A4/5) and CYP3cide (an inhibitor of CYP3A4) completely blocked the M9 formation, whereas chemical inhibitors of other P450 enzymes had little effect. Furthermore, metabolism of amlodipine in expressed human P450 enzymes showed that only CYP3A4 had significant activity in amlodipine dehydrogenation. Metabolite profiles and P450 reaction phenotyping data of a racemic mixture and S-isomer of amlodipine were very similar. The results from this study suggest that CYP3A4, rather than CYP3A5, plays a key role in metabolic clearance of amlodipine in humans.
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PMID:Amlodipine metabolism in human liver microsomes and roles of CYP3A4/5 in the dihydropyridine dehydrogenation. 2430 8