Comparative bioavailability and safety of two intramuscular ceftriaxone formulations

OBJECTIVE: To determine if two ceftriaxone solutions of different concentrations are bioequivalent when administered intramuscularly. DESIGN: Double-blind, single-dose, two-period, randomized crossover study. SETTING: A clinical research center. SUBJECTS: Seventeen healthy volunteers. INTERVENTION: Ceftriaxone 500 mg administered in either 2 or 1.4 mL of lidocaine 1% solution, with final ceftriaxone concentrations of 250 and 350 mg/mL, respectively. MAIN OUTCOME MEASURES: Blood samples were assayed for ceftriaxone concentrations with HPLC and pharmacokinetic parameters were calculated from the resulting plasma-concentration time profiles: maximum plasma concentration (Cmax) of ceftriaxone and areas under the concentration-time curve (AUC) from 0 to 36 h and 0 to infinity were the primary parameters considered in the determination of bioequivalence. RESULTS: The two solutions were generally well tolerated and had similar safety profiles. Administration of both solutions resulted in similar mean values for all pharmacokinetic parameters. Statistical analysis showed no significant differences between the two solutions in any pharmacokinetic parameter, indicating that the two solutions are statistically bioequivalent (p < or = 0.05). The 90% CI for the ratio of the means for AUC0-36 (0.86 to 1.11), AUC0.36 (0.89 to 1.14), and Cmax (0.84 to 1.12) are within the Food and Drug Administration range of bioequivalence (0.80 to 1.25). CONCLUSIONS: These results demonstrate that the more concentrated solution of ceftriaxone (350 mg/mL) is bioequivalent to the currently marketed solution of 250 mg/mL.