Thus, concomitant ingestion of phenobarbital may increase the likelihood of liver necrosis in acetaminophen overdose. Codeine should be given with caution to patients with severe respiratory depression. The depressant effect of codeine may be enhanced by the concurrent administration of sedatives and tranquilizers. In recommended therapeutic doses, acetaminophen is usually well tolerated. The incidence of gastrointestinal upset is less than after salicylate administration.
Skin rash occurs occasionally.
The rash is usually erythematous or urticarial. Average or large doses of codeine may cause various gastrointestinal symptoms such as nausea, vomiting and constipation. Caffeine may cause nausea, nervousness, insomnia, headache, vomiting, palpitation, vertigo, muscle tremor, sensory disturbances, excessive diuresis in sensitive patients. Large doses may cause gastric ulceration. Codeine and related narcotic analgesics depress respiration by action on the brain stem respiratory centres.