Quinidine with rifampin

Drugs that have been associated with elevations in quinidine concentrations include acetazolamide, the antacids magnesium hydroxide and calcium carbonate, and the H2-receptor antagonist cimetidine. Cimetidine inhibits the hepatic metabolism of quinidine. Phenytoin, rifampin, and barbiturates increase the hepatic metabolism of quinidine and reduce its plasma concentrations. 

Clinically important, potentially hazardous interactions with adefovir, alprazolam, amprenavir, anisindione, anticoagulants, buprenorphine, carbamazepine, dicumarol, dihydroergotamine, ergot, fosamprenavir, indinavir, ixabepilone, lovastatin, methadone, methysergide, midazolam, phenobarbital, phenytoin, quinidine, rifabutin, rifampin, sildenafil, simvastatin, triazolam, warfarin... 

Clinically important, potentially hazardous interactions with alprazolam, amiodarone, amphotericin B, arbutamine, bendroflumethiazide, benzthiazide, bisacodyl, bumetanide, carbimazole, chlorothiazide, chlorthalidone, cholestyramine, clarithromycin, conivaptan, cyclosporine, cyclothiazide, dan-shen, demeclocycline, devil s claw, dexmedetomidine, doxycycline, erythromycin, esomeprazole, ethacrynic acid, flunisolide, furosemide, ginseng, glycopyrrolate, glycopyrronium, hawthorn (fruit, leaf, flower extract), horsetail, hydrochlorothiazide, hydroflumethiazide, indapamide, licorice, lopinavir, mepenzolate, methyclothiazide, metolazone, minocycline, mistletoe, oxprenolol, oxytetracycline, paroxetine, phenylbutazone, polythiazide, propafenone, propantheline, quinethazone, quinidine, rabeprazole, rifampin, roxithromycin, sarsaparilla, senna, Siberian ginseng, squill, St John s wort, telithromycin, teriparatide, tetracycline, thiazide diuretics, tolvaptan, trichlormethiazide, verapamil... 

Nelfinavir (Viracept) is probably the most commonly used protease inhibitor because of its low incidence of serious adverse effects. Its most common side effects are diarrhea and flatulence these may resolve with continued use. In addition to the drugs contraindicated for use with all protease inhibitors, amiodarone, rifampin, and quinidine are contraindicated in patients taking nelfinavir. 

The pharmacokinetics of saquinavir is modified by agents that alter isoenzyme CYP3A4 of the cytochrome P-450 system and P-glycoprotein transporter. It should not be administered with midazolam, triazolam and ergot derivatives. The plasma concentrations of saquinavir are lower when coadministered with efavirenz, nevirapine or rifampin. Ritonavir reverses the effects of nevirapine on saquinavir. The coadministration of astemizole, terfenadine, amiodarone, bepridil, quinidine, propafenone or flecainide with saquinavir is also not recommended due to its potential for serious and/or life-threatening reactions. 

Inhibitors of OATP transport are typically ster-ically bulky compounds, including anions, cations, and neutral compounds (95). Various medications have been shown to interact with OATPs, including HMG CoA reductase inhibitors, cyclosporine, quinidine, rifampin, ketoconazole, verapamil, and certain protease inhibitors. Cyclosporine and rifampin have relatively high ratios of plasma concentration to Ki, suggesting the potential for clinically significant drug-drug interactions via modulation of OATP. On the other hand, plasma concentrations of pravastatin are... 

Clinically important, potentially hazardous interactions with abarelix, acenocoumarol, amisulpride, amprenavir, anisindione, anticoagulants, arsenic, astemizole, carbimazole, celiprolol, ciprofloxacin, dabigatran, degarelix, dicumarol, digoxin, diltiazem, enoxacin, fentanyl, fosamprenavir, gatifloxacin, grapefruit juice, lomefloxacin, methotrexate, moxifloxacin, nilotinib, norfloxacin, ofloxacin, oxprenolol, quinidine, quinolones, rifabutin, rifampin, rifapentine, ritonavir, simvastatin, sparfloxacin, sulpiride, tacrolimus, tipranavir, verapamil, warfarin, zuclopenthixol... 

Clinically important, potentially hazardous interactions with amiodarone, amitriptyline, amoxapine, benzodiazepines, bepridil, clomipramine, clonazepam, clorazepate, delavirdine, desipramine, diazepam, dihydroergotamine, doxepin, ergotamine, fentanyl, flurazepam, imipramine, ixabepilone, lidocaine, lorazepam, methysergide, midazolam, nortriptyline, oxazepam, phenytoin, protriptyline, quazepam, quinidine, rifampin, ritonavir, sildenafil, St John s wort, temazepam, tricyclic antidepressants, trimipramine, vitamin E... 

Clinically important, potentially hazardous interactions with amiodarone, anabolic steroids, antithyroid agents, barbiturates, bivalirudin, cimetidine, clofibrate, clopidogrel, cyclosporine, delavirdine, dextrothyroxine, disulfiram, fluconazole, glutethimide, imatinib, itraconazole, ketoconazole, metronidazole, miconazole, penicillins, phenylbutazones, piperacillin, quinidine, quinine, rifabutin, rifampin, rifapentine, rofecoxib, salicylates, sulfinpyrazone, sulfonamides, testosterone, thyroid, zileuton... 

Clinically important, potentially hazardous interactions with alfuzosin, alprazolam, amphotericin B, anisindione, antacids, aprepitant, astemizole, atorvastatin, bosentan, ciclesonide, cimetidine, clorazepate, conivaptan, cyproterone, dasatinib, dexamethasone, dicumarol, didanosine, eplerenone, erythromycin, ethotoin, fentanyl, fesoterodine, fosamprenavir, fosphenytoin, grapefruit juice, HMG-CoA reductase inhibitors, imatinib, ixabepilone, lapatinib, lopinavir, lovastatin, mephenytoin, methylprednisolone, micafungin, midazolam, nilotinib, pimozide, prednisolone, prednisone, quinidine, rifampin, rimonabant, rivaroxaban, sildenafil, silodosin, simvastatin, sirolimus, solifenacin, temsirolimus, terfenadine, tolvaptan, triazolam, vardenafil, vinblastine, vincristine, warfarin... 

Clinically important, potentially hazardous interactions with alfentanil, alfuzosin, alprazolam, amiodarone, amprenavir, aprepitant, astemizole, atazanavir, bepridil, buprenorphine, bupropion, carbamazepine, chlordiazepoxide, ciclesonide, clozapine, conivaptan, cyclosporine, cyproterone, dasatinib, diazepam, dihydroergotamine, ergot alkaloids, estazolam, eszopidone, etravirine, ezetimibe, fentanyl, fesoterodine, flecainide, flurazepam, fluticasone, halazepam, ivabradine, ixabepilone, ketoconazole, lapatinib, levothyroxine, meperidine, meptazinol, methysergide, midazolam, nifedipine, nilotinib, oral contraceptives, phenytoin, pimozide, piroxicam, propafenone, propoxyphene, quazepam, quinidine, ranolazine, rifabutin, rifampin, rifapentine, rimonabant, rivaroxaban, saquinavir, sildenafil, silodosin, simvastatin, solifenacin, St John s wort, tadalafil, temsirolimus, trabectedin, triazolam, vardenafil, voriconazole, zolpidem... 

Clinically important, potentially hazardous interactions with amiodarone, bepridil, dihydroergotamine, ergotamine, etravirine, flecainide, lovastatin, midazolam, pimozide, propafenone, quinidine, rifampin, simvastatin, St John s wort, triazolam... 

Although a less potent inducer of CYPs than rifampin, rifabutin does induce hepatic microsomal enzymes, with its administration decreasing the half-life of a number of different compounds, including zidovudine, prednisone, digi-toxin, quinidine, ketoconazole, propranolol, phenytoin, sulfonylureas, and warfarin. It has less effect than does rifampin on serum levels of indinavir and nelfinavir. 

C. Delavirdine Drug interactions are a major problem with delavirdine, which is metabolized by both CYP3A4 and CYP2D6. Its blood levels are decreased by antacids, ddl. phenytoin. rifampin, and nelfinavir. Conversely, the blood levels of delavirdine are increased by azole anti-fiingals and macrolide antibiotics. Delavirdine increases plasma levels of several benzodiazepines, nifedipine, protea.se inhibitors, quinidine, and warfarin. Delavirdine causes skin rash in up to 20% of patients, and the drug should be avoided in pregnancy since it is teratogenic in animals. 

With the introduction of RiF in 1967, the duration of combination therapy for the treatment of TB was significantiy reduced (from 18 to 9 months). Rifampin is nearly always used in combination with one or more other antitubercuiin agents. The drug is potentially hepatotoxic and may produce Gl disturbances, rash, and thrombocytopenic purpura. Rifampin is known to induce hepatic microsomai enzymes (cytochrome P450) and may decrease the effectiveness of oral contraceptives, corticosteroids, warfarin, quinidine, methadone, zidovudine, clarithromycin, and the azoie antifungai agents (see Chapter 10) (33). 

A potential case of an interaction between quinidine and flucloxacillin was demonstrated in a 63-year-old patient with recently diagnosed dilated cardiomyopathy who was admitted to the hospital with polymorphic ventricular tachycardia and ventricular fibrillation episodes induced by bradycardia. The patient was on a heart failure regimen of furosemide, spironolactone and perindopril, and was initiated on oral quinidine in the hospital for the prevention of ventricular arrhythmias. The patient s temporary pacemaker lead was removed and an implantable cardioverter-defibrillator was placed due to continued ventricular fibrillation. The next day, the patient became febrile. Culture of pacemaker lead tip and blood cultures were positive for S. aureus. Flucloxacillin and rifampin were initiated, but rifampin was discontinued due to the development of renal insufficiency and liver test abnormalities. These were normalised after rifampin was discontinued. The patient required continuous pacing to prevent ventricular tachycardia episodes, and quinidine was increased to 2800 mg per day (maximum daily dose). Quinidine plasma levels were subtherapeutic at 1.1 mg/L. The authors speculate that this interaction was due to quinidine being a substrate of Pgp and CYP3A4, and flucloxacillin s ability to induce these enzymes. While this may be a potential mechanism, the authors do not comment on how long the patient received rifampin. Rifampin is also a CYP3A4 inducer and could have been parf of fhe reason for fhe decrease in quinidine level [46 ]. 

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