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- Interactions
Selected Common Drug-Disease Interactions in Aging:
Congestive Heart Failure:
Decreased clearance of many medications
Benign Prostatic Hypertrophy:
Obstructive symptoms with anticholinergic drugs
Chronic Renal Insufficiency:
NSAIDS, aminoglycosides, contrast dye
Postural Hypotension:
May be worsened with diuretics, antihypertensives, tricyclic antidepressants, L-dopa, vasodilators, others
Dementia:
Superimposed delirium can result with anticholinergics, opiates, and psychotropic agents
Selected interactions of Drugs, Food, and Nutrition:
Drug therapy can contribute to anorexia:
digoxin, narcotics, NSAIDS, others
Dry mouth can contribute to poor intake:
clonidine, B-blockers, TCAs, antihistamines
Frequent laxative use:
fat soluble vitamin deficiencies
Food can impair absorption of:
Some medications, such as bisphosphonates
Selected Drug-Drug Interaction Examples:
Absorption; impaired by resins and fiber products
Metabolism:
cimetidine inhibits oxidative metabolism of several other medications
induction of enzymes by alcohol or phenytoin: increases metabolism of other agents cleared by the same enzymes
Renal excretion:
NSAIDS reduce renal prostaglandins and decrease renal blood flow, and thus may reduce effects of some diuretics
Competition for renal tubular secretion: (e.g. Digoxin renal excretion reduced by several other antiarrhymics)
Protein Binding changes are important for highly protein bound agents with narrow therapeutic index:
Particularly when drug is displaced and metabolism is inhibited:
Example: warfarin with sulfonamides, which both displace drug (increased free concentration) and inhibit hepatic metabolism
