Stability of an extemporaneous alcohol-free melatonin suspension

Abstract

Purpose: The stability of alcohol-free oral suspensions of melatonin 1 mg/mL, extemporaneously prepared from two commercially available melatonin tablet products, was studied.

Methods: Four 1-mg/mL melatonin suspensions were prepared. Formulations A and B contained 20 crushed 3-mg tablets of melatonin combined with a 1:1 mixture of Ora-Plus and either Ora-Sweet or Ora-Sweet SF to produce a volume of 60 mL. Formulations C and D were prepared by crushing 20 combination tablets containing melatonin 3 mg and pyridoxine hydrochloride 10 mg and then combining the powder with a 1:1 mixture of Ora-Plus and either Ora-Sweet or Ora-Sweet SF to produce a 60-mL volume. The suspensions were prepared in triplicate and stored at room temperature in amber plastic prescription bottles. Immediately after preparation and on days 7, 15, 30, 60, and 90, the samples were assayed in duplicate by stability-indicating high-performance liquid chromatography (HPLC). The samples were also evaluated for any changes in color, odor, and taste.

Results: HPLC analysis demonstrated that at least 94% of the initial melatonin concentration in formulations A and B, and at least 98% of that in formulations C and D, remained throughout the 90-day study period. Detectable changes in color, odor, or taste occurred in all of the formulations.

Conclusion: Extemporaneously prepared, alcohol-free, 1-mg/mL suspensions of melatonin and melatonin-pyridoxine hydrochloride in a 1:1 mixture of Ora-Plus and either Ora Sweet or Ora Sweet SF were stable for at least 90 days when stored in 2-oz amber plastic bottles at room temperature.