[Evaluation of preincisional mexiletine administration to alleviate postoperative pain]

Mexiletine, an antiarrhythmic agent, was preincisionally administered intravenously for the purpose of reducing postoperative pain. Twenty-eight female patients for mastectomy were studied. The patients were divided into three groups. Group 1 received no mexiletine. Group 2 received bolus administration of mexiletine 1 mg.kg-1 with additional continuous administration of 1 mg.kg-1.hr-1 for 75 minutes. Group 3 received bolus administration of mexiletine 2 mg.kg-1. The requirement of butorphanol as a postoperative analgesic within 1 hour after mastectomy in Group 3 was significantly lower than that in Group 1 (P < 0.05), but butorphanol requirement in Group 2 was not significantly lower than that in Group 1. Plasma mexiletine concentration was slightly higher in Group 3 (1.7 micrograms.ml-1) than that in Group 2 (1.0 microgram.ml-1) immediately after the intravenous mexiletine administration, although there was no significant difference. The results indicate that mexiletine 2 mg.kg-1 as preoperative bolus administration maintains its plasma concentration above 1.7 micrograms.ml-1, and is clinically effective for reducing the postoperative pain after mastectomy.