Assessment of Spectroscopic Interaction of Lamivudine/Metronidazole with Dihydroartemisinin – Piperaquine Antimalarial Tablet

In vitro interactions between dihydroartemisinin (DHA) or piperaquine (PQ) components of antimalarial dihydroartemisinin-piperaquine (DP) with lamivudine/metronidazole were studied using Fourier transform infrared spectroscopy (FTIR). One milligram of either of lamivudine or metronidazole was mixed with 1 mg of crushed and powdered DP tablet and the admixture pelletized with 20 mg potassium bromide (KBr) powder. The pellets were scanned at 2 mm/s over wavenumber region of 4000 to 500 cm-1. The bond vibrations of DHA and PQ were consistent with the reference literature values. Lamivudine shifted (C=O) bond stretching of DHA from 1735 to 1649 cm-1 and (O-H) stretching from 2926 to 2922 cm-1. The endoperoxide bond vibration was shifted from 875 to 866 cm-1. Lamivudine also shifted the characteristic aromatic (C-H) bending of PQ from 775 to 796 cm-1. The aromatic and aliphatic (C-N) stretchings were shifted from 1367 to 1384 cm-1 and 1274 to 1278 cm-1, respectively. Metronidazole shifted the (C=O) stretching of DHA from 1735 to 1643 cm-1 and lactone (C-O-O-C) stretching from 875 to 883 cm-1. The (O-H) stretching was shifted from 2926 to 2935 cm-1. Piperaquine aromatic (C-H) bending was shifted from 775 to 727 cm-1 while aromatic (C-Cl) stretching vibration from 1145 to 1143 cm-1. The vibrational spectra shifts caused by lamivudine and metronidazole on the characteristic spectra vibration of DHA and PQ were adjudged insignificant. There was no in vitro interaction between lamivudine/metronidazole and the actives of DP tablet. The drugs may not pose any biopharmaceutical implications on co-administration with DP tablet.