Therapeutic drug monitoring with valproate–Why product selection is an important factor

Total valproate versus free valproate in therapeutic drug monitoring for bipolar disorder: A cross-sectional study

INTRODUCTION

The debate about observing total versus free serum valproate levels for therapeutic drug monitoring (TDM) has been unresolved for decades. This study was planned to assess the agreement between the total versus free valproate levels and the advantage of one method over the other in TDM.

METHODS

The present cross-sectional study was done on 93 patients with bipolar disorder. The intraclass correlation coefficient, Bland Altman analysis, and Lin's concordance analysis were done to assess the agreement between the total and free valproate concentrations. Linear and polynomial models were constructed to evaluate the relation between the two measurements. Receiver operating characteristics analysis was done to compare the accuracy for differentiating remission from non-remission on Young's mania rating scale (YMRS).

RESULTS

The intraclass correlation coefficient and Lin's concordance correlation coefficient were 0.491 (p = .002) and 0.055 (95% CI:0.037, 0.073), respectively. Bland Altman's analysis showed proportional bias. A polynomial model of second order was found to be the best fit for the prediction of free valproate from the data for total valproate, and 81.4% of the variability in free valproate could be explained when adjusted for albumin levels. The area under the curve for total valproate was 0.60 when compared to free valproate 0.56 for differentiating between remission and non-remission, but the comparison between the two ROC analyses was not statistically significant.

CONCLUSION

Free valproate does not provide any added advantage over the total valproate levels; hence, total valproate levels may continue to be used as the marker for drug monitoring.

Cocrystals by Design: A Rational Coformer Selection Approach for Tackling the API Problems

Active pharmaceutical ingredients (API) with unfavorable physicochemical properties and stability present a significant challenge during their processing into final dosage forms. Cocrystallization of such APIs with suitable coformers is an efficient approach to mitigate the solubility and stability concerns. A considerable number of cocrystal-based products are currently being marketed and show an upward trend. However, to improve the API properties by cocrystallization, coformer selection plays a paramount role. Selection of suitable coformers not only improves the drug’s physicochemical properties but also improves the therapeutic effectiveness and reduces side effects. Numerous coformers have been used till date to prepare pharmaceutically acceptable cocrystals. The carboxylic acid-based coformers, such as fumaric acid, oxalic acid, succinic acid, and citric acid, are the most commonly used coformers in the currently marketed cocrystal-based products. Carboxylic acid-based coformers are capable of forming the hydrogen bond and contain smaller carbon chain with the APIs. This review summarizes the role of coformers in improving the physicochemical and pharmaceutical properties of APIs, and deeply explains the utility of afore-mentioned coformers in API cocrystal formation. The review concludes with a brief discussion on the patentability and regulatory issues related to pharmaceutical cocrystals.

Utility, promise, and limitations of liquid chromatography-mass spectrometry-based therapeutic drug monitoring in precision medicine

Therapeutic drug monitoring (TDM) is typically referred to as the measurement of the concentration of drugs in patient blood. Although in the past, TDM was restricted to drugs with a narrow therapeutic range in order to avoid drug toxicity, TDM has recently become a major tool for precision medicine being applied to many more drugs. Through compensating for interindividual differences in a drug's pharmacokinetics, improved dosing of individual patients based on TDM ensures maximum drug effectiveness while minimizing side effects. This is especially relevant for individuals that present a particularly high intervariability in pharmacokinetics, such as newborns, or for critically/severely ill patients. In this article, we will review the applications for and limitations of TDM, discuss for which patients TDM is most beneficial and why, examine which techniques are being used for TDM, and demonstrate how mass spectrometry is increasingly becoming a reliable and convenient alternative for the TDM of different classes of drugs. We will also highlight the advances, challenges, and limitations of the existing repertoire of TDM methods and discuss future opportunities for TDM-based precision medicine.