Stability of lamotrigine in two extemporaneously prepared oral suspensionsat 4 and 25 degrees C

The stability of lamotrigine 1 mg/mL in two extemporaneously prepared oral suspensions at 4 and 25 degrees C was studied. Lamotrigine tablets were ground to powder, and the powder was combined with a 1:1 mixture of Ora-Sweet and Ora-Plus or a 1:1 mixture of Ora-Sweet SF a nd Ora-Plus (Paddock Laboratories) to produce two 1-mg/mL suspensions. One 100-mg lamotrigine tablet was used to prepare one 100-mL batch of each susp ension. The suspensions were stored in amber polyethylene terephthalate pre scription bottles at 4 or 25 degrees C. Samples were collected on days 0, 7 , 14, 28, 42, 56, 70, and 91 for analysis of lamotrigine content by highper formance liquid chromatography; pH was measured, and the samples were visua lly observed against a black and white background. The mean concentration of lamotrigine was >99% of the initial concentration in all samples throughout the 91-day study period; there was no change in apparent pH, odor, or physical appearance. Lamotrigine 1 mg/mL in two extemporaneously compounded oral suspensions was stable for 91 days in polyethylene terephthalate prescription bottles at 4 and 25 degrees C.