Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Cephalexin Monohydrate

Coupling Drug Dissolution with BCS

PURPOSE

The purpose of this study is to develop a Temporal Biopharmaceutic Classification System (T-BCS), linking Finite Dissolution Time (F.D.T.) and Mean Dissolution Time (M.D.T.) for Class I/III drugs and Mean Dissolution Time for saturation (M.D.T.s.) for Class II/IV drugs.

METHODS

These parameters are estimated graphically or by fitting dissolution models to experimental data and coupled with the dose-to-solubility ratio (q) for each drug normalized in terms of the actual volume of dissolution medium (900 mL).

RESULTS

Class I/III drugs consistently exhibited q values less than 1, aligning with expectations based on their solubility, while some Class II/IV drugs presented a deviation from anticipated q values, with observations of q < 1. This irregularity was rendered to the dissolution volume of 250 mL used for biopharmaceutical classification purposes instead of 900 mL applied as well as the dual classification of some sparingly soluble drugs. Biowaivers were also analyzed in terms of M.D.T., F.D.T. estimates and the regulatory dissolution time limits for rapidly and very-rapidly dissolved drugs.

CONCLUSIONS

The T-BCS is useful for establishing correlations and assessing the magnitude of M.D.T., F.D.T., or M.D.T.s. for inter- and intra-class comparisons of different drugs and provide relationships between these parameters across all the models that were utilized.

IVIVC Revised

PURPOSE

To revise the IVIVC considering the physiologically sound Finite Absorption Time (F.A.T.) and Finite Dissolution Time (F.D.T.) concepts.

METHODS

The estimates τ and τd for F.A.T. and F.D.T., respectively are constrained by the inequality τd ≤ τ; their relative magnitude is dependent on drug's BCS classification. A modified Levy plot, which includes the time estimates for τ and τd was developed. IVIVC were also considered in the light of τ and τd estimates. The modified Levy plot of theophylline, a class I drug, coupled with the rapid (30 min) and very rapid (15 min) dissolution time limits showed that drug dissolution/absorption of Class I drugs takes place in less than an hour. We reanalyzed a carbamazepine (Tegretol) bioequivalence study using PBFTPK models to reveal its complex absorption kinetics with two or three stages.

RESULTS

The modified Levy plot unveiled the short time span (~ 2 h) of the in vitro dissolution data in comparison with the duration of in vivo dissolution/absorption processes (~ 17 h). Similar results were observed with the modified IVIVC plots. Analysis of another set of carbamazepine data, using PBFTPK models, confirmed a three stages absorption process. Analysis of steady-state (Tegretol) data from a paediatric study using PBFTPK models, revealed a single input stage of duration 3.3 h. The corresponding modified Levy and IVIVC plots were found to be nonlinear.

CONCLUSIONS

The consideration of Levy plots and IVIVC in the light of the F.A.T. and F.D.T. concepts allows a better physiological insight of the in vitro and in vivo drug dissolution/absorption processes.

A Systematic Review on the Clinical Pharmacokinetics of Cephalexin in Healthy and Diseased Populations

Cephalexin is a first-generation β-lactam antibiotic used in adults and pediatrics to treat various streptococcal and staphylococcal infections. This review aims to summarize and evaluate all the pharmacokinetic (PK) data on cephalexin by screening out all pertinent studies in human beings following the per oral (PO) route. By employing different online search engines such as Google Scholar, PubMed, Cochrane Central, and Science Direct, 23 studies were retrieved, among which nine were in healthy subjects, five in diseased ones, and the remaining were drug-drug, drug-food, and bioequivalence-related. These studies were included only based on the presence of plasma concentration-time profiles or PK parameters, i.e., maximum plasma concentration (Cmax), half-life (t1/2) area under the curve from time 0-infinity (AUC0-∞), and clearance (CL/F). A dose-proportional increase in AUC0-∞ and Cmax can be portrayed in different studies conducted in the healthy population. In comparison to cefaclor, Cmax was recorded to be 0.5 folds higher for cephalexin in the case of renal impairment. An increase in AUC0-∞ was seen in cephalexin on administration with probenecid, i.e., 117 µg.h/mL vs. 68.1 µg.h/mL. Moreover, drug-drug interactions with omeprazole, ranitidine, zinc sulfate, and drug-food interactions for cephalexin and other cephalosporins have also been depicted in different studies with significant changes in all PK parameters. This current review has reported all accessible studies containing PK variables in healthy and diseased populations (renal, dental, and osteoarticular infections, continuous ambulatory peritoneal dialysis) that may be favorable for health practitioners in optimizing doses among the latter.

Fabrication and In Vitro Drug Delivery Evaluation of Cephalexin Monohydrate-Loaded PLA:PVA/HAP:TiO2 Fibrous Scaffolds for Bone Regeneration

Owing to the excellent osteoconductive property of hydroxyapatite, we aimed to design a cephalexin monohydrate-loaded PLA:PVA/HAP:TiO₂ nanofibrous scaffold to improve the drug delivery efficiency toward bone regenerative applications. In this study, HAP:TiO₂ (anatase and rutile phases) samples were prepared by a coprecipitation method, which were later blended with PLA:PVA polymeric solution (with and without the drug) to fabricate a nanofibrous matrix via the electrospinning technique. All the prepared samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, contact angle, porosity, and tensile strength tests. Further, in vitro biodegradation and the drug-releasing ability were examined by varying the concentration of cephalexin monohydrate in the composite matrix. Deposition of the apatite layer on the scaffolds was examined after incubation in simulated body fluid solution to confirm the bioactivity of the prepared nanofibers. Biocompatibility by the MTT assay and osteogenic differentiation by ARS staining were evaluated by culturing MG63 cells on PLA:PVA/HAP:TiO₂ nanofibers, which could ensue better support for cell proliferation. Consequently, the sustained release profile and better biocompatibility of the scaffolds revealed a strong potential use in bone regenerative applications.

Formulation of Self-Nanoemulsifying Drug Delivery System of Cephalexin: Physiochemical Characterization and Antibacterial Evaluation

A cephalexin (CEP) self-nanoemulsifying drug delivery system (SNEDDS) was developed in this study to improve the drug’s oral administration. The CEP-SNEDDS was made utilizing an aqueous titration method employing Lauroglycol 90, Poloxamer 188, and Transcutol-HP. Box-Behnken design (BBD) with three factors at three levels was used for optimization, and their impacts on globule size (nm), transmittance (percent), and emulsification time (s) were assessed. The optimized formulation (Opt-F3) was further tested for zeta potential, refractive index, percent transmittance, thermodynamic stability, in-vitro release, ex vivo permeability, antibacterial activity, and bioavailability. The chosen formulation (Opt-F3) had a globule size of 87.25 ± 3.16 nm, PDI of 0.25, zeta potential of −24.37 mV, self-emulsification duration of 52 ± 1.7 s, and percentage transmittance of 99.13 ± 1.5%, viscosity of 96.26 ± 2.72 cp, and refractive index of 1.29 ± 0.1. It showed a sustained release profile (94.28 ± 5.92 percent in 24 h). The Opt-F3 formulation had 3.95 times the permeability of CEP-dispersion. In comparison to CEP-dispersion, it also demonstrated greater antibacterial efficacy against tested Gram-positive and Gram-negative pathogens. The oral bioavailability of Opt-F3 is 3.48 times higher than that of CEP-dispersion, according to an in-vivo investigation. It has been determined that the prepared CEP-SNEDDS may be an advantageous carrier for CEP delivery.

Evaluation of Excipient Risk in BCS Class I and III Biowaivers

The objective of this review article is to summarize literature data pertinent to potential excipient effects on intestinal drug permeability and transit. Despite the use of excipients in drug products for decades, considerable research efforts have been directed towards evaluating their potential effects on drug bioavailability. Potential excipient concerns stem from drug formulation changes (e.g., scale-up and post-approval changes, development of a new generic product). Regulatory agencies have established in vivo bioequivalence standards and, as a result, may waive the in vivo requirement, known as a biowaiver, for some oral products. Biowaiver acceptance criteria are based on the in vitro characterization of the drug substance and drug product using the Biopharmaceutics Classification System (BCS). Various regulatory guidance documents have been issued regarding BCS-based biowaivers, such that the current FDA guidance is more restrictive than prior guidance, specifically about excipient risk. In particular, sugar alcohols have been identified as potential absorption-modifying excipients. These biowaivers and excipient risks are discussed here.