As the weather becomes warmer, physicians may see more photosensitivity reactions due to systemic or topical drugs, perfumes, cosmetics or sunscreens. Even brief exposure to sunlight in warm or cold weather can cause intense cutaneous reactions in patients with drug-induced photosensitivity, and some patients may continue to be sensitive to sunlight long after stopping use of the offending agent.

The FDA has approved a 1% cream formulation of the antiparasitic drug ivermectin (Soolantra – Galderma) for topical treatment of inflammatory lesions of rosacea. Ivermectin is available in the US in tablets (Stromectol, and generics) for treatment of onchocerciasis and other worm infestations and as a 0.5% lotion (Sklice) for treatment of head lice.

0.5% malathion in 78% isopropanol was recently approved by the FDA for treatment of head lice.

Results from a double-blind trial suggest that off-label use of the oral antihyperglycemic drug metformin in patients with COVID-19 may decrease the risk of post-acute sequelae of SARS-CoV-2 infection ("long COVID").

On April 29, the NIH recommended against use of the antiparasitic drug ivermectin for treatment of COVID-19 outside of a clinical trial. The recommendation was made because recent randomized, placebo-controlled trials of ivermectin have produced negative results and because alternative drugs that have been shown to be effective for treatment of COVID-19 are available.

Levamisole (Janssen), an old antiparasitic drug widely used for treatment of ascariasis in animals, is now available from the National Cancer Institute (NCI) for investigational use with fluorouracil (5-FU; Adrucil; and others) as an adjuvant for treatment of resectable colon cancer that has metastasized to regional lymph nodes (Dukes stage C).

The FDA has approved the antiparasitic drug ivermectin in a 0.5% lotion (Sklice – Sanofi Pasteur) as a single-use topical treatment for head lice in patients ≥6 months old. Oral ivermectin (Stromectol – Merck) is effective for treatment of head lice resistant to other therapies, but it has not been approved by the FDA for this indication.

Rosacea is a common, chronic inflammatory facial eruption of unknown cause. It is more prevalent in women than in men, and disease onset typically occurs after age 30. Rosacea is characterized by erythema, telangiectasia, and flushing, and sometimes by recurrent, progressive crops of acneiform papules and pustules, usually on the central part of the face. Some patients develop granulomas and tissue hypertrophy, which may lead to rhinophyma (a bulbous nose), particularly in men. Blepharitis and conjunctivitis are common. Keratitis and corneal scarring occur rarely.

With increasing travel, immigration, use of immunosuppressive drugs and the spread of AIDS, physicians anywhere may see infections caused by parasites. The table in this document lists first-choice and alternative drugs for most parasitic infections.

Nitazoxanide (Alinia - Romark Labs), a new antiparasitic drug, has been approved by the FDA in a liquid formulation for treatment of diarrhea caused by Cryptosporidium parvum and Giardia lamblia in children 1 to 11 years old. It is the first drug approved for treatment of cryptosporidiosis and the first to become available as a liquid for treatment of giardiasis. The FDA is reviewing a tablet formulation of nitazoxanide for use in adults.