A formulation for oral transmucosal administration of at least one active principle with antispasmodic and/or analgesic effect, including the active principle in base form and/or in salt form, an aqueous alcohol solution titrating at least 35° alcohol by weight, the active principle being present in a state of stable and complete dissolution in the aqueous alcohol solution. Also, a method of preparing this formulation and its use for treating spastic crises.