Clarithromycin and its dangerous drug interactions


  • Colchicine: the use of these two drugs together is contra-indicated in the case of renal or hepatic impairment, otherwise dosage adjustments for colchicine are required. Clarithromycin is to be avoided if a patient is already taking colchicine for gout prophylaxis. This combination increases colchicine levels via hepatic metabolism inhibition and P-gp-mediated transporter inhibition.

  • Ergotamine: co-administration of clarithromycin and ergotamine is contra-indicated as it can lead to ergot toxicity by affecting hepatic/intestinal enzyme CYP3A4 metabolism. This fatal combination can also cause vasospasm and ischemia of the extremities and other tissues even including the CNS.

  • Indapamide: the combination is contra-indicated or if needed requires close monitoring of potassium and other electrolytes as both these drugs cause QT prolongation, and can precipitate cardiac arrhythmias (hypokalemia).

  • Statins: clarithromycin increases the toxicity risks of these lipid lowering drugs and leads to rhabdomyolysis and myalgia, reason behind the contra-indication of the combination of these drugs with clarithro.

  • Quinidine: combination can increase the quinidine levels and so raise the QT interval. Their use should be avoided and an alternative should be opted.

  • Rifabutin: the combination increases rifabutin levels and ups the risk for uveitis, leukopenia. The mechanism behind it is the inhibition of hepatic metabolism.

  • Alprazolam: the use of clarithromycin with alprazolam is a serious life-threatening interaction because this very antibiotic increase the levels of alprazolam by affecting its hepatic/intestinal enzyme CYP3A4 metabolism and this could lead to increased CNS depression and psychomotor impairment.


  • Amiodarone: clarithromycin increases the effects of amiodarone by affecting its CYP3A4 metabolism. The combo can also cause QT prolongation and cause cardiac arrhythmias. So the use of this macrolide should either be avoided with this anti-arrhythmic or if needed should be monitored closely.
  • BCG vaccine: the combination of these two drugs put the patient on high likelihood of suffering from a serious life-threatening interaction because clarithromycin decreases the effects of BCG vaccine by pharmacodynamic antagonism. The combo is contra-indicated unless benefits outweigh the risks and no other better options are available. The antibiotic treatment should be completed first and then the vaccine should be administered.
  • Digoxin: clarithromycin increases the levels of digoxin by altering intestinal flora. It applies to the oral form of both drugs. Chances of serious life threatening interaction is present that’s why alternative should be used and if there is an absence of such an alternative, the administration should be monitored closely.


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