Serious adverse interactions between drugs continue to be reported. Many of these are due to inhibition or induction of cytochrome P450 (CYP) enzymes, particularly CYP3A4. CYP3A is thought to be involved in the metabolism of more than 50 percent of currently prescribed drugs.2 CYP3A4, which is more abundantly expressed than CYP3A5, accounts for most CYP3A activity in vivo.

The FDA has approved oral and injectable formulations of the HIV-1 capsid inhibitor lenacapavir (Sunlenca – Gilead) for use with other antiretroviral drugs to treat multidrug-resistant HIV-1 infection (MDR-HIV) in heavily treatment-experienced adults whose current regimen is failing. Lenacapavir is the third drug to be approved exclusively for treatment of MDR-HIV; the intravenously administered CD4-directed antibody ibalizumab-uiyk (Trogarzo) and the orally administered HIV-1 gp120-directed attachment inhibitor fostemsavir (Rukobia) were approved earlier.

The FDA has approved a subcutaneous (SC) extended-release formulation of the mu-opioid receptor partial agonist and kappa-opioid receptor antagonist buprenorphine (Sublocade – Indivior) for once-monthly treatment of moderate to severe opioid use disorder. Sublocade is the first injectable buprenorphine product to be approved in the US. Buprenorphine is also available in sublingual formulations with or without the opioid antagonist naloxone, in a buccal formulation with naloxone, and as a subdermal implant (Probuphine).

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 Comparison Table: H2-Receptor Antagonists and PPIs

Donepezil hydrochloride (Aricept - Eisai), a piperidine-based acetylcholinesterase inhibitor, is now being marketed for oral treatment of cognitive symptoms in patients with mild to moderate dementia due to Alzheimer's disease. Donepezil is the second drug approved for this indication; tacrine hydrochloride (Cognex), also an acetylcholinesterase inhibitor, has been available in the USA for four years (Medical Letter, 35:87, 1993).

The FDA has approved tramadol hydrochloride extended-release (Ryzolt – Purdue) for treatment of moderate to moderately severe chronic pain in adults. Tramadol is already available in another extended-release formulation (Ultram ER) and in immediate-release tablets alone (Ultram, and others) and combined with acetaminophen (Ultracet, and others).

The FDA has approved oteseconazole (Vivjoa – Mycovia), a new oral azole antifungal, to reduce the incidence of recurrent vulvovaginal candidiasis (RVVC) in females with a history of RVVC. Oteseconazole is the first drug to be approved in the US specifically for treatment of RVVC.

Apremilast (Otezla – Celgene), an oral phosphodiesterase type-4 (PDE4) inhibitor, has been approved by the FDA for treatment of active psoriatic arthritis in adults. It is the fi rst PDE4 inhibitor to be approved for this indication.

The FDA recently approved the monoamine oxidase inhibitor (MAOI) selegiline in a transdermal (patch) formulation (Emsam - Bristol-Myers Squibb/Somerset) for treatment of major depressive disorder. Selegiline is also available in an oral formulation (Eldepryl, and others) for treatment of Parkinson's disease.