Disruption of tear-film homeostasis (altered composition, reduced production, rapid evaporation) and resulting ocular surface inflammation cause the discomfort and blurred vision of dry eye disease. Many cases are caused by tear evaporation due to meibomian gland dysfunction. Other precipitating factors can include lacrimal gland dysfunction, poor eyelid function, environmental factors, extended screen time, inflammatory conditions such as Sjögren's syndrome, and use of some ocular or systemic drugs such as antihistamines, retinoids, or selective serotonin reuptake inhibitors...

Concerns have arisen anew about possible use of biological weapons. The pathogens considered most likely to be used for this purpose are discussed in this article. A good source for additional information is www.usamriid.army.mil/education/bluebook.html.

Because of concerns about the possibility of bioterrorism involving smallpox, the US government is reinstituting smallpox vaccination (https://www.cdc.gov/smallpox/; www.idsociety.org/bt/toc.htm). Vaccination is currently expected to proceed in three phases: the military and hospital smallpox response teams first, other health care workers, police and firefighters second, and the general public in the third phase. Except for the military, vaccination will be...

Many different drugs are used for treatment of osteoarthritis pain, but none of them prevent progression of the disease. Nonpharmacologic approaches including weight management, exercise, tai chi, physical therapy, assistive devices, and total joint arthroplasty can also be used. The American College of Rheumatology (ACR) has published new guidelines for the management of osteoarthritis of the hip, hand, and knee.

The FDA has licensed two new pneumococcal conjugate vaccines (PCVs) for prevention of invasive pneumococcal disease in adults: Prevnar 20 (PCV20; Pfizer), which contains antigens from 20 serotypes of pneumococcus, and Vaxneuvance (PCV15; Merck), which contains antigens from 15 serotypes. Two other pneumococcal vaccines are available in the US: Prevnar 13 (PCV13; Pfizer), a 13-valent conjugate vaccine licensed for use in persons ≥6 weeks old, and Pneumovax 23 (PPSV23; Merck), a 23-valent pneumococcal polysaccharide vaccine licensed for use in persons ≥2 years...

Many prescriptions for eye drops call for instillation of 1-2 drops. But Medical Letter consultants in ophthalmology seem to agree that all eye drops should generally be given in doses of only one drop. The volume of a single drop can vary with the viscosity of the solution, the design of the dropper, and patient technique. The average volume of a drop is 35-50 microliters, but can be as high as 75 microliters. An eye brimming with fluid holds 30 microliters at best, so even one drop is often an overdose. A second either washes out the first or increases the possibility of systemic toxicity,...

The drugs of choice for treatment of fungal infections are listed in the table that begins on page 62. Some of the indications and dosages recommended here have not been approved by the FDA. More detailed guidelines for some of these infections are available online from the Infectious Diseases Society of America (www.idsociety.org).

Clostridioides (formerly Clostridium) difficile infection (CDI) is the most common infectious cause of healthcare-associated diarrhea in adults. Guidelines on management of CDI have recently been updated.

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.

Most respiratory tract infections are caused by viruses. Bacterial respiratory tract infections are usually treated empirically with antibiotic therapy that targets the most probable causative pathogens. Recommended antibiotic regimens for outpatient treatment of some common respiratory tract infections are listed in Table 1 for adults and Table 2 for children.