Amoxicillin absorption is best on an empty stomach, reaching peak plasma concentrations within 1-2 hours. Food slows absorption. Distribution is widespread, penetrating most body tissues and fluids, except for the cerebrospinal fluid unless the meninges are inflamed. It binds minimally to plasma proteins (approximately 17-20%), ensuring a high concentration of free drug available to combat infection.
Metabolism and Excretion
Amoxicillin is primarily metabolized by the liver, with a small portion excreted unchanged in the urine. About 80% of the drug is excreted via the kidneys within eight hours, primarily as inactive metabolites. Renal excretion is dependent on glomerular filtration and tubular secretion. Patients with renal impairment require dose adjustments to prevent accumulation.
Specific Considerations for Renal Impairment
For patients with reduced kidney function, dosage modifications are necessary to prevent drug accumulation and toxicity. Creatinine clearance is commonly used to guide these adjustments. Dosage reduction or extended dosing intervals are employed, ensuring safe and effective treatment. Consult prescribing information for specific guidelines based on creatinine clearance values.
