Terfenadine Quinupristin/Dalfopristin

PROPAFENONE I. ANTIARRHYTHMICS - disopyra-mide, procainamide 2. ANTIBIOTICS - macrolides (especially azithromycin, clarithromycin, parenteral erythromycin, telithromycin), quinolones (especially moxifloxacin), quinupristin/ dalfopristin 3. ANTICANCER AND IMMUNOMODULATING DRUGS -arsenic trioxide 4. ANTIDEPRESSANTS - TCAs, venlafaxine 5. ANTIEMETICS-dolasetron 6. ANTIFUNGALS-fluconazole, posaconazole, voriconazole 7. ANTIHISTAMINES - terfenadine, hydroxyzine, mizolastine 8. ANTI-M ALARIALS - artemether with lumefantrine, chloroquine, hydroxychloroquine, mefloquine, quinine 9. ANTIPROTOZOALS - pentamidine isetionate 10. ANTIPSYCHOTICS-atypicals, phenothiazines, pimozide II. BETA-BLOCKERS - sotalol 12. BRONCHODILATORS -parenteral bronchodilators 13. CNS STIMULANTS - atomoxetine Risk of ventricular arrhythmias, particularly torsades de pointes Additive effect these drugs prolong the Q-T interval. Also, amitriptyline, clomipramine and desipramine levels may be t by propafenone. Amitriptyline and clomipramine may t propafenone levels. Propafenone and these TCAs inhibit CYP2D6-mediated metabolism of each other Avoid co-administration... 

I. ANTIARRHYTHMICS - amiodarone, disopyramide, procainamide, propafenone 2. ANTIBIOTICS -macrolides (especially azithromycin, clarithromycin, parenteral erythromycin, telithromycin), quinolones (especially moxifloxacin), quinupristin/ dalfopristin 3. ANTICANCER AND IMMUNOMODULATING DRUGS-arsenic trioxide 4. ANTIDEPRESSANTS-TCAs, venlafaxine 5. ANTIEMETICS -dolasetron 6. ANTIHISTAMINES-terfenadine, hydroxyzine, mizolastine... 

In vitro studies have found that quinupristin/dalfopristin inhibits the CYP3A4-mediated metabolism of docetaxel, tamoxifen and terfenadine and is predicted to inhibit the metabolism of other drugs by this enzyme system. 

In vitro studies found quinupristin/dalfopristin inhibited the cytochrome P450 isoenzyme CYP3A4-mediated metabolism of docetaxel, tamoxifen, and terfenadine. Quinupristin/dalfopristin is predicted to raise the levels of other drugs ineluding antiarrhythmics (disopyramide, lidocaine, quinidine), antiretrovirals (such as delavirdine, indinavir, nevirapine, ritonavir), astemizole, carbamazepine, cisapride, methyl-prednisolone, paclitaxel, statins (but see Lipid regulating drugs , (p.l086)), and vinca alkaloids. More study is needed. 

Patients with hepatic insufficiency may not tolerate the drug at usual doses, however, because of increased area under the concentration curve of both parent drugs and metabolites. This may necessitate a dose reduction to 7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours in some patients. Quinupristin and dalfopristin are not metabolized by cytochrome P450 enzymes but significantly inhibit CYP 3 A4, which metabolizes warfarin, diazepam, astemizole, terfenadine, cisapride, nonnucleo- side reverse transcriptase inhibitors, and cyclosporine, among others. Dosage reduction of cyclosporine may be necessary. 

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