Acute toxic reactions to drugs of abuse continue to be important problems. Some patients may have mixed intoxications with complex combinations of signs and symptoms.

Primary hypothyroidism is usually the result of Hashimoto's (autoimmune) thyroiditis, thyroidectomy, or radioactive iodine therapy. Treatment of hypothyroidism with replacement doses of thyroid hormone is usually lifelong. Levothyroxine (LT4; synthetic thyroxine; Synthroid, and others) is the drug of choice.1

The Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA) recommend using insect repellents to avoid being bitten by mosquitoes, ticks, and other arthropods that transmit disease-causing pathogens. Repellents applied to exposed skin should be used in conjunction with other preventive measures such as wearing long-sleeved shirts, pants, and socks and avoiding outdoor activities during peak mosquito-biting times. Some insect repellents are listed in Table 1.

The recommendations for treatment of varicella-zoster virus (VZV) and herpes simplex virus (HSV) infections are listed in tables 1 and 2. Vaccination against VZV was reviewed in a previous issue.

Age-related macular degeneration (AMD) has two major forms: dry or non-neovascular (~90% of patients) and wet or neovascular (~10% of patients).

In addition to surgery and radiation therapy, a variety of drugs are used both singly and in combination to treat breast cancer. This article summarizes the principles of adjuvant therapy and treatment for metastatic disease. A summary of individual drugs and their adverse effects begins on page 3.

Antimicrobial prophylaxis can decrease the incidence of postoperative surgical site infection after some procedures. Since the last Medical Letter article on this subject, consensus guidelines have been published. Recommendations for prophylaxis in specific surgical procedures are listed in Table 1.

Excessive exposure to ultraviolet (UV) radiation can cause erythema, photoaging, and skin cancer. Sunscreens are widely used to reduce these risks, but questions remain about their effectiveness and safety. In 2021, the FDA proposed a rule that would require additional safety studies for some sunscreen active ingredients and mandate better UVA protection in sunscreen products.

This issue includes reviews of drugs for glaucoma, age-related macular degeneration (AMD), bacterial conjunctivitis, and dry eye disease. Allergic conjunctivitis is reviewed in a separate issue.

Initial treatment of allergic rhinitis (AR) depends on the severity of symptoms and whether they are intermittent or persistent (see Table 1).