Primaquine Diphosphate: Comprehensive Profile

Quantitative 1H NMR method for analyzing primaquine diphosphate in active pharmaceutical ingredients

Thermal analysis, Fourier Transform IR, the isotropic chemical shift of ¹H NMR in different solvents, their temperature dependence and spin-lattice relaxation time constant (T₁), solution 1D and 2D NMR, and solid-state ¹³C and ³¹P NMR (magic angle spinning NMR) were employed to obtain full information and elucidate the structures of primaquine diphosphate (PQD) samples used for quality controlling malaria medicines. Additionally, a simple, rapid, specific, and reliable quantitative method (qNMR) was developed to determine the PQD level in the raw material of active pharmaceutical ingredients (APIs). The method was developed using ethylene carbonate (EC) as the internal standard and dimethylsulfoxide-d₆ (DMSO-d₆) as the NMR solvent. For the API qNMR, ¹H NMR signals at 3.82 and 1.22 ppm were used. The qNMR methodology, through the linearity, range, LOD and LOQ, stability, precision, robustness, and accuracy, was validated within the requirements of guidelines. The accuracy of the qNMR was evaluated by comparing it to a pharmacopeial HPLC technique and there were no statistical differences (p > 0.05). The proposed qNMR method authentically supports and endorses the current pharmacopoeial methods used for determining the PQD content.

Optimization of primaquine diphosphate tablet formulation for controlled drug release using the mixture experimental design

A tablet formulation based on hydrophilic matrix with a controlled drug release was developed, and the effect of polymer concentrations on the release of primaquine diphosphate was evaluated. To achieve this purpose, a 20-run, four-factor with multiple constraints on the proportions of the components was employed to obtain tablet compositions. Drug release was determined by an in vitro dissolution study in phosphate buffer solution at pH 6.8. The polynomial fitted functions described the behavior of the mixture on simplex coordinate systems to study the effects of each factor (polymer) on tablet characteristics. Based on the response surface methodology, a tablet composition was optimized with the purpose of obtaining a primaquine diphosphate release closer to a zero order kinetic. This formulation released 85.22% of the drug for 8 h and its kinetic was studied regarding to Korsmeyer-Peppas model, (Adj-R(2) = 0.99295) which has confirmed that both diffusion and erosion were related to the mechanism of the drug release. The data from the optimized formulation were very close to the predictions from statistical analysis, demonstrating that mixture experimental design could be used to optimize primaquine diphosphate dissolution from hidroxypropylmethyl cellulose and polyethylene glycol matrix tablets.