Rifaximin (Xifaxan - Salix), a non-absorbed oral antibiotic derived from rifampin (Rifadin, and others), has been approved by the FDA for treatment of travelers' diarrhea caused by noninvasive strains of Escherichia coli in patients 12 years of age or older. It has been available in Europe since 1987.

Patients with frequent, severe or disabling migraine headaches may benefit from taking a drug to prevent the attacks. Beta-blockers traditionally have been the prophylactic treatment of choice, but in recent years some antiepileptic drugs such as valproate (Depakote, and others) and topiramate (Topamax) have also been used for this indication. Valproate was approved by the FDA for such use in 1996. Now topiramate has also been approved.

Duloxetine hydrochloride (Cymbalta - Lilly), a selective serotonin and norepinephrine reuptake inhibitor (SNRI) available for treatment of depression, has also been approved by the FDA for treatment of neuropathic pain associated with diabetic peripheral neuropathy (DPN). Duloxetine is one of two drugs approved specifically for management of neuropathic pain due to diabetes; the other, pregabalin (Lyrica - Pfizer), will be marketed soon and will be reviewed in the next issue of The Medical Letter.

BiDil (NitroMed), a fixed-dose combination of isosorbide dinitrate and hydralazine, was approved by the FDA for adjunctive use in the treatment of heart failure in black patients.Both drugs are oral vasodilators that have been used together off-label for many years to treat heart failure in patients not responding to other drugs.

A highly concentrated omega-3 polyunsaturated fatty acid (PUFA) preparation (Omacor - Reliant) has been approved by the FDA as an adjunct to diet for treatment of very high plasma triglyceride concentrations (>=500 mg/dL). Omacor is a combination of the ethyl esters of icosapentaenoic (EPA) and docosahexaenoic (DHA) acids. It is the first drug derived from omega-3 PUFAs to be sold by prescription.

Zolpidem (Ambien - Sanofi-Aventis), a nonbenzodiazepine benzodiazepine receptor agonist, is the most frequently prescribed hypnotic in the US. As its patent approaches expiration, its manufacturer has received FDA approval to market an extended-release formulation of the drug, Ambien CR. The pharmacological rationale for doing so is that short-acting hypnotics like zolpidem are more effective at inducing sleep than they are at maintaining it.

The FDA has approved marketing of the corticosteroid mometasone furoate in an orally inhaled dry powder formulation (Asmanex Twisthaler - Schering-Plough) for maintenance treatment of asthma in patients at least 12 years old. Mometasone is also available as a mid-potency topical corticosteroid cream (Elocon) and as an intranasal spray (Nasonex) for treatment of allergic rhinitis.

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 lubiprostone (Amitiza - Sucampo/Takeda), a chloride channel activator, for treatment of chronic idiopathic constipation in adults. The only other prescription drug approved by the FDA for this indication (in 2004 for adults <= 65 years old) is tegaserod (Zelnorm), a partial agonist of serotonin that is also approved for constipation-predominant irritable bowel syndrome in women. Of course, numerous over-the-counter products are available for treatment of constipation.

Oxymorphone hydrochloride, a semi-synthetic opioid agonist, has been available for many years in the US as Numorphan (Endo) for parenteral use and as a rectal suppository. Now it has been approved by the FDA for oral administration as an immediate-release (IR) tablet (Opana) for treatment of moderate to severe acute pain, and as an extended-release tablet (Opana ER) for treatment of moderate to severe pain in patients requiring continuous opioid treatment for an extended period of time.