Clinicians often ask about using appetite-stimulating drugs for unintentional weight loss in the elderly. Rapid weight loss in older patients is associated with a higher risk of infection, falls, fractures, and death. Causes of unintentional weight loss in the elderly include disease (e.g., cancer, infection, dental problems), psychiatric illness (e.g., depression, dementia), and socioeconomic factors (e.g., grief). Medications can cause weight loss by causing anorexia (e.g., digoxin, SSRIs, phenytoin), dry mouth (e.g., anticholinergics, loop diuretics), taste or smell disturbance (e.g., allopurinol, ACE inhibitors, calcium channel blockers), swallowing difficulties (e.g., bisphosphonates, potassium), and nausea or vomiting (e.g., iron, metformin, opioids). But in about 25% of patients, there is no identifiable cause of weight loss. The key to management is nutritional support and treating underlying problems such as depression, dental problems, etc. But when this isn't enough, appetite stimulants SOMETIMES help. These can "boost" appetite and cause modest weight gain but there's NO proof that they prolong survival.
Megestrol (Megace). The synthetic progestin megestrol acetate (Megace) is FDA approved for AIDS-associated weight loss. Dose 800 mg/day orally, administered as the oral suspension in a single dose. It can help the elderly gain weight, but any extra weight is often just fat, not muscle. In fact, lean body mass can be decreased, possibly due to drops in cortisol or testosterone. Megestrol also increases the risk of venous thrombosis. Be careful giving it to patients who are bed-bound or have a history of DVT or PE. The tablets are available in Egypt only in the 40 mg and 160 mg.
Mirtazapine (Remeron) probably stimulates appetite by blocking certain histamine and serotonin receptors. Save mirtazapine for older patients with depression, there's no proof it helps weight gain in patients who aren't depressed. Recommend giving mirtazapine at bedtime because it may cause sedation and dizziness. It poses a fall risk due to sedation, dizziness, and orthostatic hypotension. Dry mouth, constipation, and fatigue are also common side effects.
Tricyclics, cyproheptadine (Trictin), and dronabinol (Marinol) may increase appetite, but there's less evidence that they help the elderly gain weight. Cyproheptadine (Trictin) 2 mg orally twice daily or three times daily with meals. May increase over 3 weeks to a usual maintenance dose of 8 - 12 mg/day PO given in two or three divided doses. Weight gain is usually noted during the first few weeks of therapy. Avoid these due to their CNS side effects. Stop drugs if weight doesn't increase within 3 to 6 months. Also review the patient's med profile for drugs that may cause weight loss such as SSRIs, metformin and opioids.
REFERENCES
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Aoyama L, Weintraub N, Reuben DB. Is weight loss in the nursing home a reversible problem? J Am Med Dir Assoc. 2005 Jul-Aug;6(4):250-6. Available at: https://pubmed.ncbi.nlm.nih.gov/16005411
Reuben DB, Hirsch SH, Zhou K, Greendale GA. The effects of megestrol acetate suspension for elderly patients with reduced appetite after hospitalization: a phase II randomized clinical trial. J Am Geriatr Soc. 2005 Jun;53(6):970-5. Available at: https://agsjournals.onlinelibrary.wiley.com/doi/10.1111/j.1532-5415.2005.53307.x
Fox CB, Treadway AK, Blaszczyk AT, Sleeper RB. Megestrol acetate and mirtazapine for the treatment of unplanned weight loss in the elderly. Pharmacotherapy. 2009 Apr;29(4):383-97. Available at: https://pubmed.ncbi.nlm.nih.gov/19323618
