The present invention includes a transdermal composition which contains a pharmaceutically effective amount of a cannabinoid for delivery of the cannabinoid to the bloodstream of a user. The composition may comprise the following components: a surfactant-lecithin organogel; and a cannabinoid. The composition may also comprise an exogenous terpene. The cannabinoid is capable of diffusing from the composition into the bloodstream of the user, and may be used in methods for treating a patient suffering from a condition such as pain, nausea and emesis, convulsions, muscle spasm, inflammation, depression, and cachexia.