Inconstancy of "Constantly" Infused Penicillin

To the Editor:—  Penicillin is commonly administered by intravenous infusion over several hours. Physicians assume that constant volumes of drug-containing solution are delivered as long as the infusion is running. A recent study of penicillin serum levels indicated a wide fluctuation in experimental infusions, even if closely attended.¹ To document this finding in patients with infectious diseases already receiving intravenously administered penicillin, serum samples were obtained at hourly intervals from three such patients, and the amount of penicillin assayed by a disk modification of the cup-plate method with Bacillus subtilis. The hourly volume of penicillin-containing solution infused was also measured, and compared to the amount the physician had ordered. Each patient was studied twice, at first while the rate of infusion was carefully watched by one of us (D.H.), and again when the "drip" was left unattended, as is the common practice on most general medical wards. The Table