Concerns have surfaced again at the FDA and in the media about the safety of acetaminophen and the multiplicity of products on the market in the US that contain various amounts of it.

The FDA has approved a fixed-dose extended-release formulation of oxycodone and acetaminophen (Xartemis XR – Mallinckrodt) for oral treatment of acute pain severe enough to require an opioid. Oxycodone is available in the US as a single entity in oral immediate-release (Oxecta, and others) and extendedrelease (OxyContin) formulations. Immediate-release oxycodone is also available in combination with aspirin (Percodan, and others), acetaminophen (Percocet, and others), or ibuprofen (see Table 1).

The FDA has approved an extended-release oral formulation of the opioid agonist hydrocodone (Zohydro ER – Zogenix) for management of pain severe enough to require continuous, long-term therapy and for which alternative treatment options are inadequate. Zohydro ER is the first single-ingredient hydrocodone product to be marketed in the US. Hydrocodone has been available for years in combination with acetaminophen (Vicodin, and others) or ibuprofen (Vicoprofen, and others).

The FDA recently cleared the AmpliChip CYP450 Test (Roche), which analyzes blood-derived DNA to detect genetic variations in the activity of cytochrome P450 (CYP) enzymes CYP2D6 and CYP2C19 and determines the metabolizer status of the patient. The test is intended to help guide clinicians in prescribing individualized drug therapy. About 25% of all drugs, including many antidepressants and antipsychotics, are substrates of either CYP2D6 or CYP2C19. The test is being promoted initially to psychiatrists.

A fixed-dose combination of oxycodone 5 mg and ibuprofen 400 mg (Combunox - Forest Laboratories) is now available and is being heavily advertised for short-term treatment of moderate to severe acute pain.

The FDA has approved a second extended-release (ER) formulation of the oral opioid agonist hydrocodone (Hysingla ER – Purdue) for management of pain severe enough to require continuous long-term therapy and for which alternative treatment options are inadequate. Hysingla ER tablets have abuse-deterrent properties to discourage their misuse.

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 Drug Enforcement Administration (DEA) has reclassified all hydrocodone combination products as schedule II controlled substances; they were previously classified as schedule III. Hydrocodone alone (Zohydro ER) is already a schedule II controlled substance.

Alosetron hydrochloride (Lotronex - Glaxo Welcome), a selective serotonin receptor antagonist, has received FDA approval for treatment of irritable bowel syndrome (IBS) in women whose primary bowel symptom is diarrhea.