Cramp Bark Side Effects, Interactions and Warnings Cramp Bark Side Effects, Interactions and Warnings May reduce blood pressure. Cramp bark has a relaxant effect on the uterus.– Uterine relaxant properties of Viburnum. — Jarboe CH, et al. — Nature. 1966 Nov 19;212(64):837. May cause interactions with sedative or blood pressure medications. Herbal Side Effects, Interactions and Warnings Supplement Side Effects, Interactions and Warnings Prescription Drug Interactions and Warnings Prescription Information Resources Disease Information last update: March 2014
