[The geriatric pharmacology of cefazolin, cefradin and sulfisomidine]

Abstract

Clinical pharmacology of 3-(5-methyl-1,3,4-thiadiazol-2-ylthiomethyl)-8-oxo-7-(tetrazol-1-ylacetamido)-5-thia-1-azabicyclo-(4,2,0)oct-2-en-carbonic acid (cefazolin) and D-7-[2-amino-(cyclohexa-1,4-dien-1-yl)-acetamido]-3-methyl-8-oxo-5-thia-1-aza-(4,2,0)-oct-2-ene-2-carbonic acid monohydrate (cefradine) was compared in young and old adults without renal disease after i.v. injection of 1 g. Mean serum levels of cefazolin after 4 h and 6 h were significantly higher in old persons (25.0 and 14.7 mug/ml, resp.) than in young persons (16.2 and 7.8 mug/ml, resp.). Serum concentrations of cefradine after 2 and 4 h were found also higher in the aged (11.2 and 4.4 mug/ml, resp.) than in young adults. Half-life of cefazolin was prolonged from normally 94 min to 189 min, half-life of cefradine from 32 min to 72 min. Skin blister fluid punctured once for antibiotic assay contained less cefazolin in old persons (after 4 and 6 h only 22.4 and 17.4 mug/ml, resp.) than in young persons (32.7 and 27.6 mug/ml, resp.). Cefradine levels in skin blister fluid 0.5 and 1 h after i.v. injection showed also a significant difference (11.4 and 11.9 mug/ml, resp.) in old persons, 17.3 and 16.5 mug/ml, resp., in young persons). Elimination constants (alpha, beta, kel, k12, k21) were always lower in geriatric patients. Renal clearance of cefazolin was reduced from 83 ml/min to 43 ml/min, and renal clearance of cefradine from 378 ml/min to 152 ml/min. After i.v. injection of 1 g 6-sulfanilamido-2,4-dimethyl-pyrimidine (sulfisomidine) total content of the drug in blood was higher in elderly people than in young persons, but proportion of acetylated sulfisomidine was nearly the same in both groups (15%). It is supposed that higher serum levels of some drugs in old persons (over 70 years) can be explained by impaired renal excretion and slower tissue penetration of the compound from the blood.