Analgesic and psychomotor effects of thiopental at subanesthetic concentrations in human volunteers

Abstract

Our laboratory results do not support the long-held belief that barbiturates are "antanalgesic" or hyperalgesic, at least for cold-pressor-induced pain.

Comparative effects of thiopental and propofol on atrial vulnerability: electrophysiological study in a porcine model including acute alcoholic intoxication

“…The next infusion aims to replace drug lost from the circulation and hence maintain a constant plasma level. Our aim was to maintain a thiopental plasma concentration of 10-15 mg ml À1 to achieve sedation without losing spontaneous breathing 13 and responses to hypercarbia and hypoxia. 14 We employed thiopental sodium at an initial dose of 4 mg kg À1 , followed by a series of infusion steps of decremental rates from 0.3 to 0.09 mg kg À1 min À1 .…”

Thiopental Does Not Produce Hyperalgesia: A Laboratory Study Using Two Human Experimental Pain Models

“…For instance, Young (1997) found no increase in pain responses following an infusion of thiopental. Rather, with their highest dose infusion, thiopental produced reductions in pain intensity to ice immersion; notably, this analgesic effect was weaker when compared with fentanyl [17]. Banschapp and colleagues (2010) found similar results after administering the GABA A receptor agonist propofol, demonstrating marked decreases in hyperalgesic area [2].…”

“…In contrast, others have found GABA A agonists to demonstrate analgesic properties [2,[13][14][15][16]. For instance, Young (1997) found no increase in pain responses following an infusion of thiopental. Rather, with their highest dose infusion, thiopental produced reductions in pain intensity to ice immersion; notably, this analgesic effect was weaker when compared with fentanyl [17].…”

“…In addition, most investigations did not ensure double-blind procedures and lacked a placebo control. Notably, a randomized, controlled, double-blind design to assess the effects of barbiturates on pain responses has been employed in just a single study by Young et al (1997) [17], in which analgesic effects of thiopental were reported. However, interpretation of these results is constrained by the thiopental effect concentration, which, although modeled, was not measured, and by a male predominance in subject recruitment (nine males to three females).…”

“…A second deficiency in the literature is that acute experimental pain paradigms such as the ice water immersion used by Young et al [17] provide only a partial perspective of a substance's analgesic properties. In particular, central sensitization (the heightened pain response resulting when the spinal cord dorsal horn neurons become hypersensitized following a sustained afferent barrage) is not assessed by this approach.…”