Oral administration of stavudine induces hyperalgesia without affecting activity in rats

We have investigated whether long-term oral administration of the nucleoside reverse transcriptase inhibitor (NRTI) stavudine affects nociception in Sprague-Dawley rats, and whether any changes of nociception are accompanied by deterioration in activity and appetite. Stavudine (50 mg kg(-1)) was administered to rats orally once daily for six weeks in gelatine cubes. Mechanical hyperalgesia of the tail was assessed using a bar algometer, and thermal hyperalgesia by tail immersion in 49 degrees C water. Withdrawal latencies were compared to those of rats receiving placebo gelatine cubes. Withdrawal latencies to the noxious thermal challenge were not affected by stavudine, but those to the mechanical challenge were significantly decreased in rats receiving stavudine, compared to rats receiving placebo, from week three to week six of drug administration (P<0.05, ANCOVA with Newman Keuls post-hoc comparisons). The overall condition of the rats was assessed by recording daily voluntary wheel running distance and maximum running speed, food intake and body mass. Daily stavudine administration did not adversely affect voluntary running activity, appetite or growth. We have shown that long-term daily oral administration of the NRTI stavudine results in mechanical hyperalgesia in rats within three weeks without affecting appetite, growth and physical activity.