Opium and oesophageal cancer: effect of morphine and opium on the metabolism of N-nitrosodimethylamine and N-nitrosodiethylamine in the rat.

The high incidence of oesophageal cancer in Northern Iran has been associated with opium. N-Nitrosamines are the only carcinogens known to induce oesophageal cancer in animals. Ethanol, which is the major influence on oesophageal cancer incidence in the West, inhibits the first pass clearance of N-nitrosodimethylamine in animals and increases the alkylation of oesophageal DNA by oesophageal cancer-inducing N-nitrosamines. The experiments now reported were to test whether opium or morphine, which is the major alkaloid in opium, have a similar effect. It is shown that administration of morphine to rats does increase the ethylation of oesophageal DNA by N-nitrosodiethylamine and may reduce the first pass clearance of N-nitrosodimethylamine by the liver, but only at high doses of morphine.