The dried juice of the unripe seed-capsules of the white Indian poppy, Papaver somniferum.The action of opium depends upon the 20– 25 ALKALOIDS it contains. Of these, the chief is MORPHINE, the amount of which varies from around 9–17 per cent. Other alkaloids include codeine, narcotine, thebaine, papaverine, and naceine.
The importation into Britain of opium is strictly regulated under the Dangerous Drugs Acts. Similar regulations govern the sale and distribution of any preparation of morphine or diamorphine (heroin) stronger than 1 part in
500. (See DEPENDENCE.)
Action The action of opium varies considerably, according to the source of the drug and the preparation used.
In small doses, opium produces a state of gentle excitement, the person ﬁnding their imagination more vivid, their thoughts more brilliant, and their power of expression greater than usual. This stage lasts for some hours, and is succeeded by languor. In medicinal doses this stage of excitement is short and is followed by deep sleep. When potentially poisonous doses are taken, sleep comes on quickly, and passes into coma and death (see OPIOID POISONING). The habitual use of opium produces great TOLERANCE, so that opium users require to take large quantities daily before experiencing its pleasurable eﬀects. The need for opium also confers tolerance, so that people suﬀering great pain may take, with apparently little eﬀect beyond dulling the pain, quantities which at another time would be dangerous.