Effects of timing, dosage, and duration of morphine intake during pregnancy on the amount of morphine in meconium in a rat model.

Meconium drug analysis is a new and sensitive test for detecting the intrauterine exposure of infants to drugs of abuse. To explore other potential, diagnostic use of the test, we studied, in timed pregnant rats, the relationship between timing, dosage, and duration of morphine administration to the dam and the concentration of morphine, analyzed by radioimmunoassay, in their pups' meconium. The term 'meconium' refers to both the intestine and its contents. Due to the minute size of the pups' intestines, the intestinal contents were not separated from the intestines. The mean morphine concentration in meconium was found to be significantly (p < 0.05) higher in the groups treated with a higher morphine dose (10 vs. 5 mg/ kg/day), longer duration of treatment (7-20 vs. 18-20 days), or treated during the last week of gestation (14-20 vs. 1-6 or 7-13 days). We conclude that the concentration of a drug in the meconium is related to amount, timing, or duration of the drug exposure of the fetus, in utero. The quantitative analysis of drugs in the meconium, therefore, provides added information which enhances the diagnostic use of the test.