Stability of Propylthiouracil
The stability of propylthiouracil in two extemporaneously prepared suspensions at 4 and 25 °C was studied.

Commercially available 50-mg propylthiouracil tablets were used to prepare suspensions in 1:1 Ora-Sweet:Ora-Plus and in 1:1 1% methylcellulose:Simple Syrup, NF, to yield a propylthiouracil concentration of 5 mg/mL. Each suspension was stored in 10 amber plastic prescription bottles, 5 of them at 4 °C and the other 5 at 25 °C. Three samples were taken from each bottle at 0, 7, 14, 28, 42, 56, 70, and 91 days for assay by stability-indicating high-performance liquid chromatography.

More than 90% of the initial propylthiouracil concentration was retained in both suspensions for 70 days at 25 °C and for 91 days at 4 °C. There were no changes in physical appearance, color, or odor, and the pH remained essentially unchanged.

Propylthiouracil 5 mg/mL in two extemporaneously prepared oral suspensions was stable for at least 70 days at 25 °C and for at least 91 days at 4 °C.

Propylthiouracil is used in pediatric patients with hyperthyroidism. It is available as a 50-mg tablet, but no liquid dosage form is commercially available. Infants and young children cannot swallow tablets and are provided doses based on body weight. The initial dosage, 5-10 mg/kg/day in neonates and 5-7 mg/ kg/day in children, is given in three divided doses. The maintenance dosage is one third to one half of the initial dosage. The tablet must be broken or crushed to powder and the desired amount of drug mixed in some vehicle just before administration of each dose. This requires additional effort by the caregiver and creates the potential for error in drug administration. An appropriate option would be to administer doses in an extemporaneously prepared liquid dosage form. Little is known, however, about the stability of propylthiouracil in extemporaneously prepared suspensions.

The objective of our study was to determine the physical and chemical stability of propylthiouracil in two extemporaneously prepared oral suspensions stored at 4 and 25 °C.