Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.

Ciclopirox nail lacquer (Penlac - Dermik) has been approved by the FDA for treatment of mild-to-moderate onychomycosis due to Trichophyton rubrum, without involvement of the lunula. The drug has been available for many years as a lotion and cream (Loprox) for treatment of cutaneous fungal infection

Sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra, Staxyn) have become the standard treatment for erectile dysfunction. Head-to-head comparisons of these agents are still lacking, but some differences between them and new recommendations for their dosing (see Table 2) are worth noting.

Eplerenone (e pler' en one; Inspra - Pharmacia), an aldosterone receptor antagonist similar to spironolactone (Aldactone, and others), has been approved by the FDA, but not yet marketed, for treatment of hypertension. It has also been tried for treatment of heart failure.

Vardenafil (Levitra -Bayer) is the second oral drug approved by the FDA for treatment of erectile dysfunction. Sildenafil (Viagra - Medical Letter 1998; 40:51), the first oral drug, has been available for 5 years. Pharmacokinetics, effectiveness, adverse effects, dosage and cost of the new drug are reviewed. Whether it offers any benefits over sildenafil is discussed.

View the Inhibitors and Inducers of CYP Enzymes, P-Glycoprotein, and Other Transporters tables

Fexofenadine (fex oh fen' a deen) hydrochloride (Allegra - Hoechst Marion Roussel) has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis. An active metabolite of terfenadine, fexofenadine is being heavily advertised as "nonsedating...without 'black box' warnings."

Sildenafil citrate (Viagra - Pfizer) is the first oral drug approved by the FDA for treatment of erectile dysfunction. Alprostadil is also marketed for this indication but must be injected into the corpus cavemosum (Caverject) or pushed into the urethra (MUSE).

Advertisements for clemastine (Tavist-1 - Sandoz), an ethanolamine oral antihistamine, have recently appeared on television and in major newspapers in the USA. Clemastine is an old drug (Medical Letter, 21:24, 1979) that has now become available without a prescription.

Terbinafine 1% cream (Lamisil - Sandoz), an allylamine synthetic antifungal drug chemically related to naftifine (Naftin - Medical Letter, 30:98, 1988), is now available in the USA for topical treatment of tinea pedis, tinea cruris, and tinea corporis infections. An oral formulation is available in Europe and is under investigation here.