Onychomycosis is caused most commonly by Trichophyton rubrum or T. mentagrophytes. About 10% of all persons worldwide and 40% of those ≥60 years old are believed to have the disease. Risk factors include older age, diabetes, poor peripheral circulation, smoking, HIV infection, psoriasis, and immunosuppression. Left untreated, onychomycosis can cause nail plate destruction, ingrown nails, and (particularly in patients with diabetes) secondary infections. Guidelines on treatment of onychomycosis have been published.

About 2.5 million persons in the US had hepatitis C between 2017 and 2020. Guidelines from the American Association for the Study of Liver Diseases (AASLD) and the Infectious Diseases Society of America (IDSA) on management of hepatitis C virus (HCV) infection were updated in 2023.

Influenza is generally a self-limited illness, but complications including pneumonia, respiratory failure, and death can occur, especially in persons at increased risk (see Table 1).

Most patients with multiple sclerosis (MS) present with the relapsing-remitting form of the disease. Pharmacologic treatment usually includes a disease-modifying drug, corticosteroids for acute exacerbations, and other drugs for managing symptoms such as fatigue, depression, and pain. Early use of disease-modifying therapy has improved clinical outcomes.

This article includes recommendations for management of most sexually transmitted infections (STIs) other than HIV and viral hepatitis. Some of the indications and dosages recommended here have not been approved by the FDA (see Table 1).

Irritable bowel syndrome (IBS) is a common disorder characterized by recurrent abdominal pain and altered bowel habits, often accompanied by bloating. IBS is classified by its predominant bowel symptom: constipation (IBS-C), diarrhea (IBS-D), mixed type (IBS-M), or unclassified (IBS-U). Since the exact cause of IBS is unknown, the goal of treatment is symptom control. Some over-the-counter (OTC) products and prescription drugs for IBS are listed in Tables 1-4. The safety of these drugs during pregnancy and lactation is described in Table 5 (online only).

Intrauterine devices (IUDs) and the etonogestrel implant are the most effective reversible contraceptive methods available. Hormonal oral contraceptives, patches, rings, and injectables are also effective in preventing pregnancy. When used alone, barrier and behavioral methods generally have higher failure rates than other methods (see Table 1). Selection of a contraceptive method is usually based on patient-specific factors and personal preference

An oral nonopioid analgesic is often sufficient for acute treatment of mild to moderate migraine pain without severe nausea or vomiting. A triptan is the drug of choice for treatment of moderate to severe migraine in most patients without vascular disease. Treatment of pain when it is still mild to moderate in intensity improves headache response and reduces the risk of recurrence.

American College of Cardiology/American Heart Association (ACC/AHA) guidelines for treatment of hypertension were last published in 2018. Treatment of hypertensive urgencies and emergencies is not discussed here.