Following absorption, codeine is metabolized by the liver and metabolic products are excreted in the urine. Approximately 10 percent of the administered codeine is demethylated to morphine, which may account for its analgesic activity. Little unchanged drug is excreted in the urine, but most metabolic products appear in the urine within 24 hours. Acetaminophen and codeine phosphate oral solution is indicated for the relief of mild to moderate pain. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low.
Sulfite sensitivity is seen more frequently in asthmatic than in nonasthmatic people.
The respiratory depressant effects of narcotics and their capacity to elevate cerebrospinal fluid pressure may be markedly exaggerated in the presence of head injury, other intracranial lesions or a pre-existing increase in intracranial pressure. Furthermore, narcotics produce adverse reactions which may obscure the clinical course of patients with head injuries. The administration of this product or other narcotics may obscure the diagnosis or clinical course of patients with acute abdominal conditions. The patient using this drug should be cautioned accordingly. No long-term studies in animals have been performed with acetaminophen or codeine to determine carcinogenic potential or effects on fertility.