narrow therapeutic window
2 interactions related to narrow therapeutic window
alcohol + lithium
Lithium has a narrow therapeutic window and is cleared almost entirely by the kidneys. Alcohol promotes urination and dehydration, which can reduce renal lithium clearance and push serum lithium levels higher — toward the toxic range (tremor, confusion, unsteadiness, vomiting). Alcohol also independently destabilizes mood in bipolar disorder, and its early intoxication signs can mask the early warning signs of lithium toxicity.
smoking + theophylline
Combustion products in tobacco smoke induce the liver enzyme CYP1A2, speeding up how fast the body clears theophylline. Smokers therefore tend to need more theophylline to stay in range, and stopping smoking can reverse this within days and push levels into a toxic range unless the dose is reviewed.