Periactin is a prescription medication containing 4mg of Cyproheptadine HCl per tablet. It comes in a pack of 20 tablets and is manufactured by Algorithm. Cyproheptadine is an antihistamine medication that helps treat allergic reactions and other conditions as prescribed by healthcare providers. The medication comes in a white box with red and blue branding. Each tablet contains 4mg of the active ingredient Cyproheptadine HCl. The product requires a valid prescription and should only be taken under medical supervision. Store at room temperature away from moisture and heat. The medication should be taken exactly as prescribed by your healthcare provider.