Guaifenesin enhances the analgesic potency of paracetamol in mice.
OBJECTIVE
Guaifenesin is used as an expectorant and it has been reported to possess muscle relaxant and sedative activity. Guaifenesin has been used as a component of composite OTC analgesics containing paracetamol for many years. The aim of our study was to ascertain effects of guaifenesin on paracetamol analgesic activity and locomotor performance.


METHODS
Antinociceptive efficacy was tested in mice using an acetic acid (0.7%) writhing test. Locomotor performance was tested in rota-rod test and activity cage. All drugs were given orally and tested in mice.


RESULTS
In combination with a subeffective dose of guaifenesin (200 mg/kg), the ED(50) for paracetamol in the writhing test was significantly lower (82.2 mg/kg) than that of paracetamol administered alone (233.7 mg/kg). Guaifenesin alone did not show an analgesic effect. Guaifenesin did not produce statistically significant locomotor impairment in the rota-rod test at doses enhancing analgesic activity of paracetamol, although there was a trend for decreased locomotor activity in activity cage.


CONCLUSIONS
The present results indicate that guaifenesin may enhance analgesic activity of paracetamol.
Dolezal
T
T
Department of Pharmacology, 3rd Faculty of Medicine, Charles University of Prague, Ruska 87, 100 34 Prague, Czech Republic. Tomas.Dolezal@lf3.cuni.cz
Krsiak
M
M
D000082:Acetaminophen / Q000494:pharmacology*; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D004357:Drug Synergism; D006140:Guaifenesin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods
D000700:Analgesics; D000082:Acetaminophen; D006140:Guaifenesin