Cimetidine Calcium-channel blockers

CIMETIDINE CALCIUM CHANNEL BLOCKERS t levels of calcium channel blockers, especially diltiazem and nifedipine Inhibition of CYP3A isofbrm-mediated metabolism Monitor BP closely be aware of possibility of significant l BP. Consider l dose of diltiazem and nifedipine by up to 50%... 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

Agents that may increase theophylline levels include allopurinol, beta blockers (nonselective), calcium channel blockers, cimetidine, oral contraceptives, corticosteroids, disulfiram, ephedrine, influenza virus vaccine, interferon, macrolides, mexiletine, quinolones, thiabendazole, thyroid hormones, carbamazepine, isoniazid, and loop diuretics. 

Drugs that may affect tacrolimus include nephrotoxic agents (aminoglycosides, amphotericin B, cisplatin, cyclosporine), antifungals, bromocriptine, calcium channel blockers, cimetidine, clarithromycin, danazol, diltiazem, erythromycin, methylprednisolone, metoclopramide, carbamazepine, phenobarbital, phenytoin, rifamycins, cisapride, chloramphenicol, metronidazole, nefazodone, omeprazole, protease inhibitors, macrolide antibiotics, fosphenytoin, and St. John s wort. 

Coadminister known CYP3A4 inhibitors (eg, erythromycin, itraconazole, ketoconazole, fluconazole, calcium channel blockers, cimetidine) with caution in patients with widespread or erythrodermic disease. 

Cimetidine [NP] Decreased metabolism of calcium channel blockers. 

In contrast, decreases in theophylline metabolism by selective inhibitors of CYP1A2, such as fluvoxamine and some quinolone antibiotics, or by selective and potent inhibitors of CYP3A4, such as the macrolide antibiotics, have resulted in serious theophylline toxicity (22). It is postulated that taken over time, the macrolide antibiotics act as mechanism-based inhibitors of CYP isoforms other than just CYP3A4. Some nonselective inhibitors of P450s, such as cimetidine, some p-blockers and calcium channel blockers, and others (19,22), also appear to inhibit the metabolism of theophylline enough to cause toxicity. 

Omeprazole, like cimetidine, can impair benzodiazepine metabolism and lead to adverse effects (SEDA-18, 43). Other drugs, including antibiotics (erythromycin, chloramphenicol, isoniazid), antifungal drugs (ketoconazole, itraconazole, and analogues), some SSRIs (fluoxetine, paroxetine), other antidepressants (nefazodone), protease inhibitors (saquinavir), opioids (fentanyl), calcium channel blockers (diltiazem, verapamil), and disulfiram also compete for hepatic oxidative pathways that metabolize most benzodiazepines, as well as zolpidem, zopiclone, and buspirone (SEDA-22,39) (SEDA-22,41). 

ALCOHOL CALCIUM CHANNEL BLOCKERS 1. Acute alcohol ingestion may t hypotensive effects. Chronic moderate or heavy drinking 1 hypotensive effects 2. Verapamil may t peaked serum concentration and prolong the effects of alcohol 1. Additive hypotensive effect with acute alcohol excess. Chronic alcohol excess is associated with hypertension 2. Uncertain at present, but presumed to be due to inhibition of the hepatic metabolism of alcohol, a mechanism similar to that with cimetidine, ranitidine and aspirin 1. Monitor BP closely as unpredictable responses can occur. Advise patients to drink alcohol only in moderation and to avoid large variations in the amount of alcohol drunk 2. Warn patients about potentiation of the effects of alcohol, particularly the risks to driving... 

An impressive list of compounds has been used to decrease cisplatin nephrotoxicity [ANF, glycine, diethyldithiocarbamate, calcium channel blockers, cimetidine, sodium thiosulphate, glutathione, other sulfidryl compounds,. ..]. Among them only sodium thiosulphate has received a significant clinical application and has been reported to reduce the renal toxicity of cisplatin administered locally by either the intra-arterial, intra-peritoneal or intrathoracic routes [50, 51]. However, controversies still exists as to the effect of sodium thiosulphate on cisplatin antitumor activity. Thus sodium thiosulphate may be most useful in combination with intraperitoneal cisplatin where it confers renal protection without altering local effects of cisplatin [51]. 

CYP3A4 alprazolam, calcium channel blockers, cisapride, clarithromycin, cyclosporin A, erythromycin, HIV protease inhibitors, lidocaine, midazolam, simvastatin, terfenadine carbamazepine, dexamethsone, phenobarbital, phenytoin, rifampicin, St John s wort cimetidine, erythromycin, grapefruit juice, HIV protease inhibitors, itraconazole, ketoconazole... 

A4 Amiodarone, azole antifungals, cimetidine, clarithromycin, cyclosporine, erythromycin, fluoroquinolones, grapefruit juice, HIV protease inhibitors, metronidazole, quinine. SSRIs, tacrolimus Antiarrhythmics, antidepressants, azole antifungals, benzodiazepines, calcium channel blockers, cyclosporine, delavirdine, doxorubicin, efavirenz, erythromycin, estrogens, HIV protease inhibitors, nefazodone. paclitaxel, proton pump inhibitors, HMG-CoA reductase inhibitors, rifabutin, rifampin, sildenafil, SSRIs, tamoxifen, trazodone, vinca anticancer agents... 

A. Cimetidine, and to a lesser extent ranitidine, reduces hepatic clearance and prolongs the elimination half-life of several dmgs as a result of inhibition of cytochrome P-450 activity and reduction of hepatic blood flow. Examples of drugs affected include phenytoin, theophylline, phenobatbital, cyclosporine, morphine, lidocaine, calcium channel blockers, tricyclic antidepressants, and warfarin. 

The plasma levels of diltiazem, isradipine and nifedipine are increased by cimetidine and it may possibly be necessary to reduce the dosages of these calcium-channel blockers. High doses of cimetidine may increase the bioavailability of lercanidipine. Although studies surest no important interactions occur between nicardipine or nisoldipine and cimetidine, the manufacturers advise caution. Plasma felodipine, lacidipine, nimodipine, and... 

No adverse interaction was seen in 22 patients given calcium-channel blockers, including nicardipine, with oral famotidine for 6 to 8 weeks. No changes in the pharmacokinetics or pharmacodynamics of a 12-hour intravenous infusion of nicardipine 24 mg were seen in 12 healthy subjects given intravenous cimetidine 300 mg every 6 hours for 48 hours. ... 

The interactions of cimetidine with diltiazem and nifedipine are established. Concurrent use need not be avoided but the increase in the calcium-channel blocker effects should be taken into account. It has been suggested that the dosage of diltiazem should be reduced by 30 to 50% " and that of nifedipine by 40 to 50%. " The interaction between verapamil and cimetidine is not well established, but monitor the effects until more is known. It has been suggested that the verapamil dose may need to be reduced by 50%. Monitoring is advised if isradipine is given with cimetidine and a reduction in isradipine dose may be required. ... 

Ranitidine does not interact significantly with diltiazem, nimodipine, nisoldipine or nifedipine, and is possibly a non-interacting alternative for cimetidine with other calcium-channel blockers. Note that the nitrendipine AUC was increased by 50% and 89% by ranitidine, although this was not considered clinically relevant. 

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