Clarithromycin; Erythromycin/Phenobarbital; Phenytoin Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

When these two medicines are taken together, your body may process your antibiotic more quickly and your seizure medication more slowly.

What might happen:

The blood level of your antibiotic may decrease, so it may not work as well. The amount of seizure medication in your blood may increase and cause more side effects than usual.

What you should do about this interaction:

Let your healthcare professionals (e.g. doctor or pharmacist) know you are taking these medicines together. Let your doctor know if your infection doesn't seem to be getting better. If you experience nausea, vomiting, confusion, dizziness, or other symptoms, contact your healthcare professional. It may be necessary to measure the blood levels of your seizure medicine. Your doctor may want to adjust the dose.Your healthcare professionals may already be aware of this drug interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Hafner R, Bethel J, Power M, Landry B, Banach M, Mole L, Standiford HC, Follansbee S, Kumar P, Raasch R, Cohn D, Mushatt D, Drusano G. Tolerance and pharmacokinetic interactions of rifabutin and clarithromycin in human immunodeficiency virus-infected volunteers. Antimicrob Agents Chemother 1998 Mar;42(3):631-9.
  • 2.Burger DM, Meenhorst PL, Mulder JW, Kraaijeveld CL, Koks CH, Bult A, Beijnen JH. Therapeutic drug monitoring of phenytoin in patients with the acquired immunodeficiency syndrome. Ther Drug Monit 1994 Dec;16(6):616-20.
  • 3.Milne RW, Coulthard K, Nation RL, Penna AC, Roberts G, Sansom LN. Lack of effect of erythromycin on the pharmacokinetics of single oral doses of phenytoin. Br J Clin Pharmacol 1988 Sep;26(3):330-3.
  • 4.Bachmann K, Schwartz JI, Forney RB Jr, Jauregui L. Single dose phenytoin clearance during erythromycin treatment. Res Commun Chem Pathol Pharmacol 1984 Nov;46(2):207-17.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.