Drotaverine hydrochloride

Drotaverine hydrochloride is a type 4 cyclic nucleotide phosphodiesterase (PDE4) inhibitor, and is an antispasmodic drug, used to enhance cervical dilation during childbirth. Drotaverine hydrochloride is structurally related to papaverine drotaverine not only relaxed the precontracted tracheal preparations but also decreased mediator-induced contraction. These effects of drotaverine were concentration dependent, with a significantly higher potency on the KCl-induced response, than on either the histamine or methacholine induced one. A similar result was noted for nifedipine. The PDE inhibitor, theophylline, also relaxed the precontracted preparations but was ineffective on the mediator-induced contraction in a physiologically relevant concentration range.