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.

Atazanavir (Reyataz - Bristol-Myers Squibb), a new protease inhibitor (PI), and emtricitabine (Emtriva - Gilead), a nucleoside analogue reverse transcriptase inhibitor (NRTI) chemically similar to lamivudine, have been approved by the FDA for treatment of HIV-1 infection. Both are taken once daily, unlike most anti-HIV drugs.

The FDA has approved the dipeptidyl peptidase-4 (DPP-4) inhibitor alogliptin (Nesina – Takeda) for treatment of type 2 diabetes. In addition to the single-ingredient product, the FDA also approved fixed-dose combinations of alogliptin/metformin (Kazano) and alogliptin/pioglitazone (Oseni) for the same indication. Alogliptin is the fourth DPP-4 inhibitor to become available in the US. The other three – saxagliptin (Onglyza), sitagliptin (Januvia), and linagliptin (Tradjenta) – are also available in fixed-dose combinations with metformin.

Lefamulin (Xenleta – Nabriva), a semisynthetic pleuromutilin antibiotic, has been approved by the FDA for IV and oral treatment of community-acquired bacterial pneumonia (CABP) in adults. It is the first systemic pleuromutilin antibiotic to be approved in the US; retapamulin (Altabax), a 1% topical ointment for treatment of impetigo, was approved in 2007.

The FDA has approved vonoprazan, a potassium-competitive acid blocker, copackaged with amoxicillin (Voquezna Dual Pak – Phathom) and with amoxicillin and clarithromycin (Voquezna Triple Pak) for treatment of Helicobacter pylori infection in adults. Vonoprazan is the first potassium-competitive acid blocker to be approved in the US. It has been available in Japan for treatment of various acid-related disorders since 2014. Vonoprazan is not available alone in the US.

About 2.5 million persons in the US had hepatitis C between 2017 and 2020. Guidelines from the American Association for the Study of Liver Diseases (AASLD) and the Infectious Diseases Society of America (IDSA) on management of hepatitis C virus (HCV) infection were updated in 2023.

When used for the appropriate seizure type, antiseizure medications (ASMs) are roughly equivalent in efficacy. In addition to the seizure type, the choice of drug is usually based on factors such as ease of use, spectrum of activity, adverse effects, interactions with other drugs, presence of comorbid conditions, suitability for elderly persons and those with childbearing potential, and cost. Treatment should begin with a single drug, increasing the dosage gradually until seizures are controlled or adverse effects become unacceptable. If seizures persist, expert clinicians generally...

The drugs of choice for treatment of viral infections (other than HIV) and their dosages are listed in Tables 1-6 on the pages that follow. Some of the indications and dosages recommended here have not been approved by the FDA. Vaccines used for the prevention of viral infections are discussed elsewhere.