Reference

Plasma codeine and morphine concentrations after therapeutic oral doses of codeine-containing analgesics

Plasma codeine and morphine concentrations after therapeutic oral doses of codeine-containing analgesics. Findlay, John W. A.; Jones, Evelyn C.; Butz, Robert F.; Welch, Richard M. (Wellcome Res. Lab., Dep. Med. Biochem., Research Triangle Park, N.C., USA). Clin. Pharmacol. Ther., 24(1), 60-8 (English) 1978. CODEN: CLPTAT. ISSN: 0009-9236. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacodynamics) Plasma concns. of codeine (I) and morphine [57-27-2] were detd. by specific radioimmunoassays in healthy human subjects at various times following oral administration of analgesic prepns. contg. therapeutic doses of I phosphate [52-28-8]. Following administration of I phosphate (60 mg) in combination with aspirin (650 mg) or acetaminophen (600 mg) to 2 sep. groups, mean peak I plasma concns. and b-phase elimination half-lives were 159 ng/mL and 2.9 h or 138 ng/mL and 2.4 h, resp. Mean max. concns. of metabolically produced morphine were 6.8 ng/mL (aspirin-I phosphate administration) and 7.4 ng/mL (acetaminophen-I phosphate). Following drug administration, the mean ratio of the areas under the resp. plasma concn.-time curves for morphine and I was 0.095 for the aspirin-I phosphate study and 0.12 for the acetaminophen-I phosphate study. Thus, free morphine represented about 10% of the free I area in each case. Thus, metabolically produced morphine may influence or be responsible for the analgesic efficacy of I.

Lack of inhibition of paracetamol absorption by codeine

Lack of inhibition of paracetamol absorption by codeine. Bajorek, P.; Widdop, B.; Volans, G. (Dep. Pharmacol., Guy's Hosp., London, Engl.). Br. J. Clin. Pharmacol., 5(4), 346-8 (English) 1978. CODEN: BCPHBM. ISSN: 0306-5251. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacodynamics) In normal volunteers, oral administration of codeine phosphate [52-28-8] (15 mg) 30 min previously did not influence the absorption of paracetamol [103-90-2] (1000 mg, orally).