<unk>  is metabolized by enzymes of the cytochrome P450 system, in particular, by isozymes of the CYP3A superfamily. The activity of the CYP3A enzymes can be induced or inhibited by certain drugs (e.g., dexamethasone), which can cause it to affect the metabolism of many different drugs, including<unk> . If other CYP3A substrates — drugs that are broken down by CYP3A — such as simvastatin (Zocor), lovastatin (Mevacor), or atorvastatin (Lipitor)—are taken concomitantly with<unk> , levels of the substrates increase, often causing adverse effects. A noted drug interaction involves<unk>  and simvastatin, resulting in increased simvastatin levels and the potential for rhabdomyolysis. Another group of CYP3A4 substrates are drugs used for migraine such as<unk> gotamine and dihydroergotamine; their adverse effects may be more pronounced if<unk>  is associated. Earlier case reports on sudden death prompted a study on a large cohort that confirmed a link between<unk> , ventricular tachycardia, and sudden cardiac death in patients also taking drugs that prolong the metabolism of<unk>  (like verapamil or diltiazem) by interfering with CYP3A4. Hence,<unk>  should not be administered to people using these drugs, or drugs that also prolong the QT interval. Other examples include terfenadine (Seldane, Seldane-D), astemizole (Hismanal), cisapride (Propulsid, withdrawn in many countries for prolonging the QT time) and pimozide (Orap). Theophylline, which is used mostly in asthma, is also contraindicated.<unk>  and doxycycline can have a synergistic effect when combined and kill bacteria (E. coli) with a higher potency than the sum of the two drugs together. This synergistic relationship is only temporary. After approximately 72 hours, the relationship shifts to become antagonistic, whereby a 50/50 combination of the two drugs kills less bacteria than if the two drugs were administered separately. It may alter the effectiveness of combined oral contraceptive pills because of its effect on the gut flora. A review found that when<unk>  was given with certain oral contraceptives, there was an increase in the maximum serum concentrations and AUC of estradiol and dienogest.<unk>  is an inhibitor of the cytochrome P450 system, which means it can have a rapid effect on levels of other drugs metabolised by this system, e.g., warfarin.
Erythromycin
Cethromycin
Methicillin
Ampicillin
Meropenem
Clarithromycin
Natamycin
Cefotaxime