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.

The FDA has approved an extended-release intramuscular suspension formulation of the gonadotropin-releasing hormone (GnRH) agonist triptorelin (Triptodur – Arbor/Debiopharm) for twice-yearly treatment of central precocious puberty (CPP) in children ≥2 years old. Triptorelin has been available in the US for years as Trelstar for palliative treatment of advanced prostate cancer. Before the approval of Triptodur, Trelstar was used off-label for treatment of CPP.

Older patients are especially susceptible to drug-induced cognitive impairment. They are more likely to be taking multiple drugs, to have higher blood levels of those drugs because of renal or hepatic dysfunction, and to have pre-existing cognitive problems that make it difficult to detect the role of drugs causing new symptoms or making old ones worse.

The FDA has approved a long-acting fixed-dose combination of the stimulant dexmethylphenidate and the prodrug serdexmethylphenidate (Azstarys – Corium) for once-daily treatment of attention-deficit/hyperactivity disorder (ADHD) in patients ≥6 years old. Azstarys is the first product containing serdexmethylphenidate to become available in the US.