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July 27, 1964

Pentazocine vs Morphine

Author Affiliations

Stanford, Calif

JAMA. 1964;189(4):332. doi:10.1001/jama.1964.03070040082032

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To the Editor:—  Cass and associates, after carrying out a controlled study of the analgesic effects of pentazocine and morphine in man (JAMA188:112 [April 13] 1964), concluded that "Pentazocine in 40 mg dosage approaches though is not equal to the analgesic effectiveness of morphine sulfate 20 mg." From the data presented in Table 1 of their communication it is possible to calculate total pain relief (Clin Pharmacol Ther1:163, 1960), ie, the areas between the time effect curves and baseline shown in their Fig 2. The totals of one-, two-, three-, and four-hour observations are as follows: morphine 20 mg = 7.99, pentazocine 20 mg = 4.11, pentazocine 40 mg = 5.80. When these data are plotted on semi-log paper and extrapolated to an equal effect level it is apparent that the best graphic estimate of an equivalent dose of 20 mg of morphine would be approximately 90 mg of

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