This study compared the penetration of moxalactam and cefazolin into the human atrial appendage after simultaneous administration of both drugs by two routes. Nineteen adult patients scheduled for coronary vein bypass surgery randomly received 10 mg of moxalactam and cefazolin per kg by either the intramuscular or intravenous (bolus) route on administration of anesthesia. Concentrations of cefazolin in serum were significantly greater than concentrations of moxalactam at all times for both routes of administration. There were no significant differences, however, in the concentration of these drugs in atrial appendages, although concentrations of both agents administered intravenously were significantly greater than of drugs administered intramuscularly. (19.3 ± 10.3 and 21.0 ± 11.0 jxg/g intravenously versus 8.3 ± 3.6 and 10.1 ± 3.2 ,ug/g intramuscularly for moxalactam and cefazolin, respectively).We recently reported that the pharmacokinetics of moxalactam and cefazolin in normal adults are as distinctive after simultaneous intravenous infusion as they are after separate infusion, and we proposed that the method of simultaneous administration may have significant advantages for comparisons of the penetration of antibiotics into tissue (8). This study was designed to compare the atrial appendage penetration of moxalactam with that of cefazolin after simultaneous administration by either the intravenous (i.v.) or the intramuscular (i.m.) route.
MATERIALS AND METHODSSubjects and drug administration. A total of 19 adult patients, 15 males and 4 females, ranging from 45 to 76 years in age and from 52 to 111 kg in weight, scheduled for coronary vein bypass surgery, were included in this study and gave informed consent. None had a history of bypass surgery or allergy to ,B-lactam antibiotics. All patients had normal serum creatinine levels (<1.4 mg/dl) except two (1.5 and 2.9 mg/dl), and all patients had normal serum bilirubin levels ('1.1 mg/ dl) at the time of surgery. Patients were allocated by a table of random numbers to receive both antibiotics by either the i.m. route (9 patients) or the i.v. route (10 patients).Lot 3TU65A of cefazolin sodium and lot CT-4765-OM of moxalactam disodium (Eli Lilly & Co., Indianapolis, Ind.) were used in this study. Immediately before surgery, the antibiotics were reconstituted with bacteriostatic normal saline or sterile water for injec-* To whom requests for reprints should be addressed. (804) 786-7625 tion according to the manufacturer's recommendation (3.0 and 2.5 ml/g for moxalactam and cefazolin, respectively). The resulting assumed concentrations were 270 mg/ml for moxalactam and 330 mg/ml for cefazolin. A dose of 10 mg of each drug per kg was given to each subject. Both moxalactam and cefazolin were given at the same time into either a rapidly running i.v. line over 1 to 2 min (bolus study) or separately into each deltoid muscle shortly after beginning anesthesia. The mean time (with standard deviation) between drug administration and removal of the atrial appendage was 4...
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