Zidovudine with rifabutin

Didanosine, stavudine and zalcitabine are not expected to interact with rifabutin, but rifabutin may modestly increase the clearance of zidovudine. An isolated case describes undetectable rifabutin levels in a patient taking antiretrovirals including buffered didanosine. 

LiRC,Nightii ale S, Lewis RC, Colburn DC, NarangPK. Lack of effect of concanitant zidovudine on rifabutin kinetics in patients with AIDS-related ccmplex. Antmncrob Agents... 

A 35-year old Caucasian man with AIDS and multiple opportunistic infections, including Mycobacterium kansasii and Mycobacterium avium complex (MAC) disease developed moderate to severe primary sensorineural hearing loss after 4—5 months of therapy with oral azithromycin 500 mg/day. Other medications included ethambutol, isoniazid, rifabutin, ciprofloxacin, co-trimoxazole, fluconazole, zidovudine (later switched to stavudine), lamivudine, indinavir, methadone, mod-ified-release oral morphine, pseudoephedrine, diphenhydramine, megestrol acetate, trazodone, sorbitol, salbutamol by metered-dose inhaler and nebulizer, ipratropium, and oral morphine solution as needed. Significant improvement of the hearing impairment was documented 3 weeks after drug withdrawal. 

Clinically important, potentially hazardous interactions with abacavir, atorvastatin, bepridil, bupropion, carbamazepine, clarithromycin, cyclosporine, dexamethasone, digoxin, felodipine, fluticasone propionate, fosamprenavir, itraconazole, ketoconazole, lovastatin, methadone, midazolam, nicardipine, nifedipine, phenobarbital, phenytoin, rifabutin, simvastatin, sirolimus, St John s wort, systemic lidocaine, tacrolimus, tenofovir, trazodone, vinblastine, vincristine, voriconazole, warfarin, zidovudine... 

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. 

Ritonavir exhibits additive to synergistic effects against HIV when used in combination with reverse-transcriptase inhibitors such as zidovudine or zalcitabine. Ritonavir pro-dnces a large increase in the plasma concentration of amio-darone, astemizole, bepridil, bupropion, cisapride, clozapine, encainide, flecainide, meperidine, peroxicam, propafenone, propoxyphene, quinidine, rifabutin, and terfenadine. 

Items 6-7 A patient with AIDS has a CD4 count of 45/ xL. He is being maintained on a three-drug regimen of indinavir, zalcitabine, and zidovudine. For prophylaxis against opportunistic infections, he is also receiving cidofovir, fluconazole, rifabutin, and trimethoprim-sulfamethoxazole. 

Items 92-93. A 30-year-old hospitalized AIDS patient has a CD4 cell count of 50/ tL. He is being treated with a highly active antiretroviral therapy (HAART) regimen consisting of zidovudine (ZDV), lamivudine (3TC), and indinavir. Other drugs being administered to this patient include acyclovir, clarithromycin, foscamet, rifabutin, and trimethoprim-sulfamethoxazole. 

The pharmacokinetics of rifabutin are not affected by the concurrent use of zidovudine in AIDS patients, " and rifabutin does not affect the pharmacokinetics of zidovudine in HIV-positive patients, although one review found a trend towards increased zidovudine clearance. No increase in adverse effects appears to occur when rifabutin is given with zidovudine."... 

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