The effects of physostigmine 1 mg I V were studied on the analgesia, sedation and reduction in respiratory rate induced by morphine 10mg/60kg 1 v in 10 patients recovering from surgery. Within 5–10min, physostigmine abolished the somnolent effect of morphine and restored the respiratory rate to pre-drug values Analgesia, assessed by an independent observer and by the patient was, if anything, increased by physostigmine. The analeptic effect of physostigmine lasted 40–60 min