Christopher K. Finch, PharmD

Penicillin-induced neurotoxicity was first recognized by Johnson and Walker in 1945 after intraventricular administration of benzylpenicillin.1,2 Subsequently, the β-lactams have been shown to have a higher rate of CNS effects than other classes of antibiotics.3,4

Carbamazepine is associatedwith numerousclinically significantdrug interactions.1 Thiswidely used agent ismost commonly prescribed for eitherseizure disorders or adjunctivepain management.

For more than 30 years, serumdigoxin concentrations (SDCs)have been monitored toensure safe, effective therapy.1,2Although the therapeuticrange for SDCs is often listed as either0.8 to 2.0 ng/mL or 0.5 to 2.0ng/mL, the results of clinical trials inthe 1990s suggest an upper limit of1.0 ng/mL for treatment of heart failure.3-11 An upper limit for the SDC of1.0 ng/mL is also recommendedfor patients who have heart failureand atrial fibrillation with rapid ventricularresponse.

Rifampin is associated with numerousclinically significantdrug interactions.1-4 New interactionswith rifampin-aswell as rifabutin-continue tobe reported in studies and clinical observations.Here we present highlightsof our recent update on the interactionsthat are most relevant toprimary care practice.5

A focus on the known clinically significant drug-drug interactions of phenytoin.

Phenytoin is one of the most commonly prescribed antiepileptic drugs in both acute and chronic settings; its use has been extensively described. Nevertheless, interactions between phenytoin and numerous other drugs continue to complicate seizure therapy; these have been documented in case reports, studies, textbooks, and epilepsy reviews.

Azole antifungals are widelyused to treat numerousinfections.1 Manywell-documented, clinicallysignificant drug interactionsare associated with these agents1,2