narrow therapeutic index
3 interactions related to narrow therapeutic index
taurine + lithium
Taurine has weak diuretic and natriuretic activity in the kidney, which can theoretically alter renal clearance of lithium and shift serum lithium concentrations. Because lithium has a narrow therapeutic window and is cleared almost entirely by the kidneys, any agent affecting renal sodium handling can change steady-state levels and increase the risk of toxicity or therapeutic failure.
lithium + caffeine
Caffeine increases renal clearance of lithium by promoting natriuresis and increasing glomerular filtration, so chronic caffeine intake lowers lithium blood levels. A sudden reduction in caffeine intake can raise serum lithium into the toxic range, while abruptly increasing caffeine can lower levels and worsen mood symptoms.
caffeine + theophylline
Caffeine and theophylline are closely related methylxanthines that share the CYP1A2 metabolic pathway and compete for the same adenosine receptors. Concurrent use can raise theophylline levels and add pharmacodynamically to cause tachycardia, tremor, nausea, seizures or arrhythmias.