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We conducted a double-blind cross-over study in ten volunteers aged from 19 to 30 years, to compare the pain control effects of a single oral dose of two analgesic compounds (drug A: propyphenazone mg 250, ethylmorphine mg 5, caffeine mg 5; drug B: dipyrone mg 500, diphenhydramine mg 12.5, adiphenine mg 5, ethyl aminobenzoate mg 2.5) in an experimental pain model using stimulation of dental pulp. Constant voltage stimuli were delivered through silver chloride electrodes placed in contact with the vestibular surface of the upper medial incisor. At the beginning of the session, the pain input was graded by asking the subject to identify the weakest stimulus perceived (threshold level) and the strongest stimulus endurable (tolerance level). The range between threshold and tolerance level was divided in nine steps plus a subliminal step. The ten steps were delivered randomly, and each series of steps was repeated eight times. The subjects were instructed to rate the pain sensation in an arbitrary scale of 5 degrees. The procedure was repeated at 60 min and 180 min after drug administration. Each subject received two tablets of drug A or drug B in two different sessions at weekly intervals. Statistical analysis of the procedures showed that neither drug A nor drug B significantly affected the pain threshold. Drug A significantly reduced the total pain score (P less than 0.01) and its action peaked 60 min after administration.(ABSTRACT TRUNCATED AT 250 WORDS)