Benzathine penicillin G: a model for long-term pharmacokinetic comparison of parenteral long-acting formulations.

WHAT IS KNOWN AND OBJECTIVE:   Long-acting intramuscular penicillin G injection is an important product for the management of some severe infections. However, testing the bioequivalence of such long-acting formulations is difficult. Our aim was to undertake such a test using a generic formulation containing 1 200 000 IU of benzathine penicillin G powder and an innovator's product (Retarpen(®) 1·2 million units; Sandoz, Switzerland). METHODS:   In an open, double-blind, randomized, two-periods, two-group crossover study, 12 healthy male volunteers received both formulations of benzathine penicillin G on two different days with a 5-month washout period between the doses and a sampling period of over 500 h. A simple, sensitive and rapid high-performance liquid chromatography (HPLC)-UV method was developed and validated for determination of penicillin G plasma concentrations and other pharmacokinetic (PK) parameters. RESULTS AND DISCUSSION:   The analytical method used produced linear responses within a wide analyte concentration range with average within-run and between-run variations of below 15% with acceptable recovery, accuracy and sensitivity. The primary PK parameters we used were maximum plasma concentration (Cmax ), time to reach the maximal concentration (Tmax ) and the area under the plasma concentration vs. time curve from time zero to the last sampling time (AUC0→t ) using a standard non-compartmental approach. Based on these parameters, the two formulations were bioequivalent. WHAT IS NEW AND CONCLUSION:   We illustrate the bioequivalence testing of a very long-acting product. The data indicate that the generic test formulation and the branded reference formulation were bioequivalent in fasting healthy Iranian male volunteers.

Stationary cuvette: a new approach to obtaining analytical curves by UV-VIS spectrophotometry.

BACKGROUND: Investigations in the field of pharmaceutical analysis and quality control of medicines require analytical procedures that achieve suitable performance. An analytical curve is one of the most important steps in the chemical analysis presenting a direct relationship to features such as linearity. OBJECTIVE: This study has the aim of developing a new methodology, the stationary cuvette, to derive analytical curves by spectroscopy for drug analysis. METHODOLOGY: The method consists basically of the use of a cuvette with a path length of 10 cm, containing a constant volume of solvent in which increasing amounts of a stock solution of the sample are added, droplet by droplet. After each addition, the cuvette is stirred and the absorbance is measured. This procedure was compared with the currently used methodology, which requires a labour-intensive dilution process, and possible sources of variation between them were evaluated. RESULTS: The results demonstrated that the proposed technique presented high sensitivity and similar reproducibility compared with the conventional methodology. In addition, a number of advantages were observed, such as user-friendliness, cost-effectiveness, accuracy, precision and robustness. CONCLUSION: The stationary cuvette approach may be considered to be an appropriate alternative to derive analytical curves for analysing drug content in raw materials and medicines through UV-VIS spectrophotometry.

Treatment of latent syphilis in HIV-infected patients with 10 d of benzylpenicillin G benethamine: a prospective study in Maputo, Mozambique.

Neurosyphilis has been reported in HIV-infected patients previously treated with penicillin G benzathine, which does not achieve treponemicidal levels in cerebrospinal fluid. Therapy combining benzylpenicillin G and its repository form benzylpenicillin G benethamine could be a potentially effective alternative enhanced regimen for treating latent syphilis in HIV-infected patients because peak serum and cerebrospinal fluid concentrations would be achieved early post-administration by the former molecule and sustained for 24 h due to the prolonged half-life of the latter. In this study, 23 asymptomatic HIV and Treponema pallidum co-infected patients received 10 d of combined therapy (2 M IU intramuscular once daily) and were followed up at 3, 6 and 12 months. None experienced side effects or clinical symptoms. Of the 18 patients who were evaluated 1 y later, 8 (44.4%) exhibited serological treatment failure, defined as a positive serum rapid plasma reagin test. In conclusion, a 10-d regimen combining penicillin G and penicillin G benethamine seems to be of no benefit compared to currently recommended treatment.

Colloidal carriers for benzathine penicillin G: nanoemulsions and nanocapsules.

The main purpose of this work is to formulate benzathine penicillin G nanoemulsion and nanocapsules, to evaluate their physicochemical and stabilising characteristics, and to determine their antimicrobial activity and penicillin in vitro release kinetics. Nanoemulsions were produced by the spontaneous emulsification approach and nanocapsules of poly (D,L-lactic acid-co-glycolic acid) polymer (PLGA) were prepared by the method of interfacial deposition of a pre-formed polymer. A 207+/-8 nm mean diameter nanoemulsion formulation maintained stability for more than 5 months at 4 degrees C. Stable nanocapsules with 224+/-58 nm mean diameter were obtained, which remained stabilised over 120 days at 4 degrees C. The penicillin encapsulation ratio in the nanocapsules was 85%. The in vitro release profiles indicated that penicillin released from the nanoemulsion was similar to the one observed from nanocapsules. However it can be clearly deduced from the in vitro kinetic analysis that the antibiotic cannot be protected in colloidal delivery systems. Nevertheless, stable formulations obtained in this investigation supply a potential dosage form to encapsulate more easily soluble drugs.