Analgesic Effect of Acetylsalicylic Acid (ASA) Versus a Lithium-ASA combination: An Evoked Potential Study Employing Radiant Heat Stimulation with a CO₂Laser

Abstract

Objective experimental algesimetry was used to assess quantitative differences in analgesic properties between acetylsalicylic acid (ASA, 750 mg) and a special combination of ASA, trilithium citrate and quinine-2 HCl (750 mg, 126 mg, 4.5 mg) in a placebo-controlled double-blind crossover study on nine healthy subjects. Radiant heat stimulation was applied with a CO2 laser and somatosensory evoked vertex potentials (LSEP) were recorded while the subjects were simultaneously engaged in an adaptive pursuit tracking task in order to stabilize their vigilance. The N1 amplitude of the LSEP decreased under both verum medications; however, the drug combination was significantly more effective. The time course of this effect was attended by a marked intradiurnal variation of the LSEP amplitudes. The role of lithium in the combination with ASA and quinine-2 HCl (Togal) and an amplification of the analgesic potency of ASA are discussed.