A review of 17 studies that assessed specific drug interactions in elderly patients found that 16 of the studies reported an elevated risk for hospitalization in older adults associated with drug interactions.
These interactions included angiotensin-converting enzyme (ACE) inhibitors and potassium-sparing diuretics; ACE inhibitors or angiotensin receptor blockers and sulfamethoxazole/trimethoprim (SMX/TMP); benzodiapines or zolpidem and other medications; calcium channel blockers and macrolide antibiotics; digoxin and macrolide antibiotics; lithium and loop diuretics or ACE inhibitors; phenytoin and SMX/TMP; sulfonylureas and antimicrobial agents; theophylline and ciprofloxacin; and warfarin and antimicrobial agents or non-steroidal anti-inflammatory drugs.
The researchers concluded that when the elderly receive drug therapy, it should be absolutely necessary for the achievement of well-defined goals. They also recommend that an evidence-based, high-priority list of drug interactions in the elderly be developed and maintained.
For more info, see Hines, L.E. et al. (2011). Potentially harmful drug-drug interactions in the elderly: A review. American Journal of Geriatric Pharmacotherapy, 9, 364-377.