The FDA has approved a new 550-mg tablet of rifaximin (Xifaxan – Salix), a minimally absorbed oral antibiotic, to reduce the risk of recurrent hepatic encephalopathy (HE). A 200-mg tablet has been available for treatment of travelers’ diarrhea since 2004.

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.

The FDA has approved a conjugated polysaccharide vaccine, Menactra (Sanofi-Pasteur), for protection against disease caused by Neisseria meningitidis in people 11-55 years old, and the manufacturer has applied for approval for use in children 2 to 10 years old. An unconjugated meningoccocal polysaccharide vaccine (Menomune - Sanofi-Pasteur) has been licensed in the US since 1981.

Several readers have asked the Medical Letter to evaluate the effectiveness and safety of exogenous melatonin for treatment of insomnia and jet lag. Melatonin has not been approved by the US Food and Drug Administration (FDA), but is available in health food stores and apparently is being used as self-medication to treat a wide variety of disorders.

Six vaccines are recommended for routine use in adults living in the USA (Guide for Adult Immunization, 2nd ed, Philadelphia:American College of Physicians, 1990). Immunization recommendations for travel outside the USA were published in The Medical Letter, volume 32, page 33, April 6, 1990.

Mefloquine hydrochloride (Lariam - Roche), a new antimalarial drug chemically related to quinine, has been approved by the US Food and Drug Administration (FDA) for prevention and treatment of Plasmodium falciparum and P. vivax malaria.

Men with primary or secondary hypogonadism require lifelong androgen replacement to prevent osteoporosis and maintain normal muscle mass, erythropoiesis and sexual function (AM Matsumoto, Endocrinol Metab Clin North Am, 23:857, 1994). Until recently, the standard treatment for male hypogonadism has been an intramuscular injection of a long-acting testosterone ester every two to three weeks, which leads to serum testosterone concentrations that are high for a few days, normal for a few days more, and then may be subnormal until the next dose. Two transdermal preparations of testosterone...

The Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA) recommend using insect repellents to prevent infections transmitted by mosquitoes and ticks. Insect repellents applied to exposed skin should be used in conjunction with other preventive measures such as wearing pants and long-sleeved shirts and avoiding outdoor activities during peak mosquito-biting times. Mosquitoes can transmit diseasecausing pathogens, including Zika, chikungunya, dengue, West Nile, eastern equine encephalitis, and yellow fever viruses, and the malaria parasite....

Armodafinil (Nuvigil – Cephalon), the R-enantiomer of the non-amphetamine stimulant modafinil (Provigil – Cephalon; Alertec – Shire in Canada), is being promoted directly to the public for treatment of excessive daytime sleepiness associated with shift work.