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.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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Implanon (Organon), an implantable contraceptive containing the progestin etonogestrel, has been approved by the FDA. Two other implantable contraceptives, Norplant and Jadelle, which both contain levonorgestrel, are FDA-approved but not marketed in the US.

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 Triumeq (Viiv Healthcare), a fixed-dose combination of the integrase strand transfer inhibitor (INSTI) dolutegravir and the nucleoside reverse transcriptase inhibitors (NRTIs) abacavir and lamivudine, for once-daily treatment of HIV-1 infection. Dolutegravir (Tivicay) was approved as a single agent in 2013.

Tipranavir (Aptivus - Boehringer Ingelheim), a new protease inhibitor, has received accelerated approval from the FDA. It must be given with ritonavir (Norvir). The combination is indicated for use with other antiretrovirals to treat HIV infection in highly treatment-experienced adults who have ongoing viral replication or in those with HIV strains known to be resistant to multiple protease inhibitors.

Darunavir (Prezista - Tibotec), a new protease inhibitor, has received accelerated approval from the FDA for use in combination therapy of human-immunodeficiency virus (HIV) infection in previously treated adults. It is coadministered with low-dose ritonavir (Norvir), which increases its bioavailability.

Raltegravir (Isentress - Merck), the first in a new class of oral HIV drugs called HIV-1 integrase strand transfer inhibitors (InSTI), has received accelerated FDA approval for use in combination therapy for treatment-experienced adults infected with HIV-1 strains resistant to multiple antiretroviral agents.

Maraviroc (Selzentry - Pfizer), the first CCR5 (CC chemokine receptor 5) antagonist has received the same FDA approval but is restricted to use in adults with CCR5-tropic HIV-1 ("R5 virus"). A commercial assay is available for R5 tropism.

Artesunate for injection (Amivas LLC), a semi-synthetic artemisinin derivative, is now approved by the FDA for initial (induction) treatment of severe malaria in children and adults. It has been available from the CDC on a compassionate use basis since 2007. Artemether/lumefantrine (Coartem), another artemisinin-based drug, was approved earlier for oral treatment of uncomplicated Plasmodium falciparum malaria. IV artesunate is now the only FDA-approved injectable antimalarial drug available in the US; IV quinidine has been discontinued.