The in vitro activity of teicoplanin, a new antibiotic related to vancomycin, was determined against 456 gram-positive cocci. The activity of teicoplanin in comparison with that of vancomycin was similar against staphylococci but 4 to 40 times higher against enterococci and I8-hemolytic and viridans streptococci. The single-dose pharmacokinetics of teicoplanin were studied in six healthy volunteers after administration of 3 and 6 mg/kg intravenously and of 3 mg/kg intramuscularly. The kinetic parameters after both intravenous doses were very similar. The curves for concentration in plasma for the 3-and 6-mg/kg intravenous doses showed a triexponential decline with elimination half-lives of 47.3 and 44.1 h, respectively. The percentages of the doses recovered in urine (0 to 102 h) were 43.2 and 44.1%, respectively. The areas under the plasma curves were dose related: 256.5 and 520.9 ,tg/h per ml, respectively. The bioavailability of teicoplanin after injection of 3 mg/kg intramuscularly was 90%, and the peak level was 7.1 ,ug/ml. The mean levels in plasma 24 h after the 3-mg/kg doses were 2.1 and 2.3 ,ug/ml, respectively, and the mean level in plasma 24 h after the 6-mg/kg intravenous dose was 4.2 ,ug/ml.Teicoplanin is a glycopeptide antibiotic related to vancomycin and ristocetin. It has formerly been described as teichomycin A2, one of the major components of a complex of antibiotics produced by Actinoplanes teichomyceticus nov. sp. ATCC 31121 (1, 16). Teicoplanin is active in vitro and in vivo against gram-positive microorganisms (2,5,7,8,11,12,14,15,18 with inocula of 105 to 106 CFU per spot delivered by a multipoint inoculator. Growth of the streptococci (except for Streptococcus faecalis) was supported with 5% lysed horse blood added to the medium. The antibiotics were tested in twofold serial dilutions at concentrations ranging from 0.004 to 128 ,ug/ml. The plates were incubated overnight at 36°C, except those containing oxacillin and inoculated with staphylococci, which were incubated at 30°C for 24 h. The MIC was read as the lowest concentration of antibiotic which allowed no visible growth.Pharmacokinetic study design. Six healthy male volunteers participated in this study after providing informed consent. They ranged in age from 22 to 23 years and averaged 74.3 ± 6.4 kg (mean ± standard deviation) in weight and 1.93 ± 0.10 m2in surface area; mean creatinine clearance was 108.4 + 14.9 ml/min. They were considered to be normal on the basis of medical history, renal and liver function tests, comnplete blood count, and urinalysis. A history of hypersensitivity to drugs was not present in any of the study subjects.Teicoplanin was administered in a triple-crossover design at the following intravenous and intramuscular doses (strictly adjusted per kilogram of body weight): 3 and 6 mg/kg (in 20 ml of physiological saline) intravenously (i.v.) through a forearm vein as a slow (5-min) bolus injection, and 3 mg/kg (as 100 mg/ml saline solution) intramuscularly (i.m.), deep in the lateral gluteal region. The dif...