SYNDOL

Codeine is a centrally acting weak analgesic. Codeine exerts its effect through μ opioid receptors, although codeine has low affinity for these receptors, and its analgesic effect is due to its conversion to morphine. Codeine, particularly in combination with other analgesics such as paracetamol, has been shown to be effective in acute nociceptive pain. The anti-tussive activity of codeine is probably due to its depressant effect on the medullary cough centre in the brain.

Paracetamol is a medication used to treat pain and fever. It does appear to selectively inhibit COX activities in the brain, which may contribute to its ability to treat fever and pain.

Doxylamine, an ethanolamine, first-generation antihistamine crosses the blood-brain barrier and exerts an antiemetic action by selectively binding to H₁ receptors in the brain. Doxylamine is an antihistamine commonly used as a sleep aid. This drug is also used to relieve symptoms of hay fever (allergic rhinitis), hives (rash or itching), and other allergic reactions. Doxylamine is also a potent anticholinergic.

Caffeine is structurally related to the methylxanthines theophylline and theobromine. Caffeine’s main action is as a CNS stimulant.