Lamivudine is known to exhibit polymorphism and the needle-shaped crystals are named as Form I and the bipyramidal crystals as Form II. The FT-Raman spectrum of lamivudine Form II and I shows characteristic bands at 798, 463 cm -1 and 697 cm -1 Raman shifts, respectively. FT-Raman spectroscopy method combined with chemometrics was developed for quantitative analysis of lamivudine Form II in lamivudine Form I drug substance. Solid mixtures of Form I and Form II shows the relative intensity of the characteristic bands at 798, 463 and 697 cm -1 were proportional to the relative amounts of Form I and Form II in mixtures. A calibration was made which is linear in the range from 1.0 to 20.0 % (w/w) of Form II in Form I. The results indicate that levels down to 3.0 % (w/w) of Form II could be quantified using this non-destructive approach, with less than 1.5 % (w/w) limit of detection.

A simple FT-Raman spectroscopic method was developed for identification of finasteride polymorph form in finished dosage form. Finasteride polymorph form I was used in the tablet preparation and the weight fraction of finasteride in tablet was only about 0.023. The method was successfully used to identify the polymorphic form of finasteride in tablet and also to detect up to a level of about 15% of the other polymorph of finasteride present in the solid dosage. The dosage form was characterized by different techniques i.e. powdered X-ray diffraction, infrared spectroscopy and Raman spectroscopy. Based on literature survey, only Raman spectroscopy method is able to identify the polymorph of finasteride in dosage form.