Clinically Relevant Drug-Drug Interactions in Primary Care.

Drug interactions are common in the primary care setting and are usually predictable. Identifying the most important and clinically relevant drug interactions in primary care is essential to patient safety. Strategies for reducing the risk of drug-drug interactions include minimizing the number of drugs prescribed, re-evaluating therapy on a regular basis, considering nonpharmacologic options, monitoring for signs and symptoms of toxicity or effectiveness, adjusting dosages of medications when indicated, and adjusting administration times. Inhibition or induction of cytochrome P450 drug metabolizing isoenzymes is the most common mechanism by which clinically important drug interactions occur. The antimicrobials most likely to affect the international normalized ratio significantly in patients receiving warfarin are trimethoprim/sulfamethoxazole, metronidazole, and fluconazole. An empiric warfarin dosage reduction of 30% to 50% upon initiation of amiodarone therapy is recommended. In patients receiving amiodarone, limit dosages of simvastatin to 20 mg per day and lovastatin to 40 mg per day. Beta blockers should be tapered and discontinued several days before clonidine withdrawal to reduce the risk of rebound hypertension. Spironolactone dosages should be limited to 25 mg daily when coadministered with potassium supplements. Avoid prescribing opioid cough medicines for patients receiving benzodiazepines or other central nervous system depressants, including alcohol. Physicians should consider consultation with a clinical pharmacist when clinical circumstances require the use of drugs with interaction potential.

Vision Loss in Older Adults.

Vision loss affects 37 million Americans older than 50 years and one in four who are older than 80 years. The U.S. Preventive Services Task Force concludes that current evidence is insufficient to assess the balance of benefits and harms of screening for impaired visual acuity in adults older than 65 years. However, family physicians play a critical role in identifying persons who are at risk of vision loss, counseling patients, and referring patients for disease-specific treatment. The conditions that cause most cases of vision loss in older patients are age-related macular degeneration, glaucoma, ocular complications of diabetes mellitus, and age-related cataracts. Vitamin supplements can delay the progression of age-related macular degeneration. Intravitreal injection of a vascular endothelial growth factor inhibitor can preserve vision in the neovascular form of macular degeneration. Medicated eye drops reduce intraocular pressure and can delay the progression of vision loss in patients with glaucoma, but adherence to treatment is poor. Laser trabeculoplasty also lowers intraocular pressure and preserves vision in patients with primary open-angle glaucoma, but long-term studies are needed to identify who is most likely to benefit from surgery. Tight glycemic control in adults with diabetes slows the progression of diabetic retinopathy, but must be balanced against the risks of hypoglycemia and death in older adults. Fenofibrate also slows progression of diabetic retinopathy. Panretinal photocoagulation is the mainstay of treatment for diabetic retinopathy, whereas vascular endothelial growth factor inhibitors slow vision loss resulting from diabetic macular edema. Preoperative testing before cataract surgery does not improve outcomes and is not recommended.

Vision loss in older persons.

Family physicians have an essential role in assessing, identifying, treating, and preventing or delaying vision loss in the aging population. Approximately one in 28 U.S. adults older than 40 years is visually impaired. Vision loss is associated with depression, social isolation, falls, and medication errors, and it can cause disturbing hallucinations. Adults older than 65 years should be screened for vision problems every one to two years, with attention to specific disorders, such as diabetic retinopathy, refractive error, cataracts, glaucoma, and age-related macular degeneration. Vision-related adverse effects of commonly used medications, such as amiodarone or phosphodiesterase inhibitors, should be considered when evaluating vision problems. Prompt recognition and management of sudden vision loss can be vision saving, as can treatment of diabetic retinopathy, refractive error, cataracts, glaucoma, and age-related macular degeneration. Aggressive medical management of diabetes, hypertension, and hyperlipidemia; encouraging smoking cessation; reducing ultraviolet light exposure; and appropriate response to medication adverse effects can preserve and protect vision in many older persons. Antioxidant and mineral supplements do not prevent age-related macular degeneration, but may play a role in slowing progression in those with advanced disease.