Background and Objectives Spinal mepivacaine has been reported as a reliable anesthetic for ambulatory anesthesia. Its pharmacologic properties are midway between those of bupivacaine and lidocaine, and it can be used in intermediate duration ambulatory surgical procedures.

Methods A patient taking clonidine transdermal patches (TTS) to control high blood pressure received spinal mepivacaine for surgical repair of a ruptured meniscus with arthroscopy.

Results The resulting duration of sensory and motor block were 12 and 8.5 hours, respectively. These are more than four times as long as the reported mean durations with this spinal local anesthetic. We hypothesized that the use of clonidine via TTS for the previous 16 months contributed to this unusual delay of recovery from spinal anesthesia.

Conclusions Clonidine can increase the duration of spinal anesthetics. Even though this well-known effect has been considered mostly beneficial, it can be an adverse effect when spinal ambulatory anesthesia is given to patients receiving clonidine TTS or clonidine in other forms for long-term treatment of hypertension or other diseases.