CODEINE PHOSPHATE

Chemical properties

White or almost white, crystalline powder or small, colourless crystals.

Originator

Actacode Linctus,Sigma

The Uses of CODEINE PHOSPHATE

Antitussive; analgesic (narcotic).

brand name

Ambenyl Cough Syrup (Parke-Davis); Colrex Compound (Solvay Pharmaceuticals).

Therapeutic Function

Narcotic analgesic, Antitussive

Clinical Use

Codeine is used extensively to treat moderate to mild pain. Codeine is a weak μ agonist, but approximately 10% of an oral dose (30–60 mg) is metabolized to morphine, which contributes significantly to its analgesic effect. The plasma half-life of codeine after oral dose is 3.5 hours. The dose of codeine needed to produce analgesia after parenteral dose causes releases of histamine sufficient to produce hypotension, pruritus, and other allergic responses. Thus, administration of codeine by parenteral route is not recommended.

Veterinary Drugs and Treatments

In small animal medicine, codeine is used principally as an oral analgesic when salicylates are not effective and parenteral opiates are not warranted. It may also be useful as an antitussive or an antidiarrheal.

Drug interactions

Potentially hazardous interactions with other drugs
Antibacterials: metabolism increased by rifampicin.
Antidepressants: possible CNS excitation or depression with MAOIs - avoid concomitant use, and for 2 weeks after stopping MAOI; possible CNS excitation or depression with moclobemide; increased sedative effects with tricyclics.
Antihistamines: increased sedative effects with sedating antihistamines.
Antipsychotics: enhanced hypotensive and sedative effects.
Dopaminergics: avoid with selegiline.
Nalmefene: avoid concomitant use.
Sodium oxybate: enhanced effect of sodium oxybate - avoid.

Metabolism

Codeine is metabolised by O- and N-demethylation in the liver to morphine, norcodeine, and other metabolites including normorphine and hydrocodone. Metabolism to morphine is mediated by the cytochrome P450 isoenzyme CYP2D6, which shows genetic polymorphism.
Codeine and its metabolites are excreted almost entirely by the kidney, mainly as conjugates with glucuronic acid.