MEDizzy - In most patients, an antibiotic is eliminated 25% by hepatic

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General principles of drug action in pharmacology

In most patients, an antibiotic is eliminated 25% by hepatic metabolism, 50% by renal filtration, and 25% by biliary excretion. If the normal maintenance dose rate is 5 10 mg/hour, what dose rate will you administer to a patient 12 normal with a creatinine clearance that is (assume that hepatic and biliary clearances are normal)?

ExplanationMaintenance dose rate 5 (clearance) × (desired plasma concentration), and the whole body clearance is the sum of all the individual organ clearances. In most patients, the hepatic metabolism, renal filtration, and biliary excretion account for 25%, 50%, and 25% of the whole body clearance, respectively. Since the creatinine clearance in this patient indicates that the renal filtration is only half normal, the renal clearance of the drug will be decreased by half. This means that the whole body clearance will be 75% of that of normal (25% hepatic, 25% renal, and 25% biliary). Therefore, the dose should also be 75% of the standard dose.