Saliva versus plasma bioequivalence of rusovastatin in humans: validation of class III drugs of the salivary excretion classification system

Detection and quantification of prostaglandin E2 in saliva by liquid chromatography-tandem mass spectrometry using microextraction by packed sorbent

The detection of eicosanoids in saliva samples can assist pharmacokinetic/pharmacodynamic studies due to the facility of obtaining samples, minimal discomfort and high adherence of volunteers to the study. The present study enabled determine prostaglandin E₂ concentrations in saliva samples, using a microextraction by packed sorbent methodology and subsequent detection in liquid chromatography-tandem mass spectrometry. Twelve volunteers underwent scaling and coronary-radicular polishing of the upper molars and sequential saliva collections: 0.25-96 h after ingestion of a 600 mg ibuprofen tablet, to quantify prostaglandin E₂ concentrations. There was an increase in the level of prostaglandin E₂ with a significant difference after the dental procedure (0.25 h) compared to 11, 24, 48 and 72 h (*p < 0.05). After taking the drug, these levels begin to decrease up to 5 h, returning to normal in the subsequent hours. The method was developed and validated with linearity between 2.4 and 1250 ng/mL and r2 above 0.9932. The limit of quantitation was about 2.4 ng/mL. The coefficients of variation and the relative standard errors of the accuracy and precision analyzes were < 15%. The proposed extraction and analysis methodology proved to be efficient, fast and promising for pharmacokinetic/pharmacodynamic assays after using anti-inflammatory drugs.

In Vitro Dissolution and in Silico Modeling Shortcuts in Bioequivalence Testing

Purpose: To review in vitro testing and simulation platforms that are in current use to predict in vivo performances of generic products as well as other situations to provide evidence for biowaiver and support drug formulations development. Methods: Pubmed and Google Scholar databases were used to review published literature over the past 10 years. The terms used were “simulation AND bioequivalence” and “modeling AND bioequivalence” in the title field of databases, followed by screening, and then reviewing. Results: A total of 22 research papers were reviewed. Computer simulation using software such as GastroPlus™, PK-Sim^® and SimCyp^® find applications in drug modeling. Considering the wide use of optimization for in silico predictions to fit observed data, a careful review of publications is required to validate the reliability of these platforms. For immediate release (IR) drug products belonging to the Biopharmaceutics Classification System (BCS) classes I and III, difference factor (ƒ₁) and similarity factor (ƒ₂) are calculated from the in vitro dissolution data of drug formulations to support biowaiver; however, this method can be more discriminatory and may not be useful for all dissolution profiles. Conclusions: Computer simulation platforms need to improve their mechanistic physiologically based pharmacokinetic (PBPK) modeling, and if prospectively validated within a small percentage of error from the observed clinical data, they can be valuable tools in bioequivalence (BE) testing and formulation development.

Comparative assessment of saliva and plasma for drug bioavailability and bioequivalence studies in humans

Aims: To study the pharmacokinetics of selected drugs in plasma and saliva matrixes in healthy human volunteers, and to suggest using non-invasive saliva sampling instead of plasma as a surrogate in bioavailability and bioequivalence (BA/BE) studies.

Methods: Four different pilot BA/BE studies were done in 12–18 healthy humans. Saliva and plasma samples were collected for 3–5 half life values of metformin, tolterodine, rosuvastatin, and paracetamol after oral dosing. Saliva and plasma samples were assayed using LC-MSMS, and then pharmacokinetic parameters were calculated by non-compartmental analysis using Kinetica program. Effective intestinal permeability (P_eff) values were also optimized to predict the actual average plasma profile of each drug by Nelder-Mead algorithm of the Parameter Estimation module using SimCYP program.

Results: All studied drugs showed salivary excretion with strong correlation coefficients between saliva and plasma concentrations. The optimized P_eff ranged 1.44–68.3 × 10⁻⁴ cm/s for the drugs under investigation. Saliva/plasma concentrations ratios ranged 0.17–1.5. Inter and intra individual variability of primary pharmacokinetic parameters in saliva matrix was either close to or higher than plasma matrix. This requires larger sample size in saliva studies for some drugs.

Conclusion: Our results suggest that there is a potential in BA/BE studies for saliva to be considered as a surrogate for plasma concentration, which goes along with drug regulations. The use of saliva instead of plasma in such studies makes them non-invasive, easy and with a lower clinical burden.