Chimps in an open-air forested enclosure have spotted veterinarian Raven Jackson carrying a caddy packed with their morning's juice treats and frozen bananas. A half-dozen dark-haired chimpanzees crowd the wire metal gate and wait for her to dispense the goodies.
Codeine is a narcotic. It is a pain reliever and a cough suppressant. Promethazine is an antihistamine. It blocks the effects of the naturally occurring chemical histamine in your body. The combination of codeine and promethazine is used to treat cold or allergy symptoms such as runny nose, sneezing, and cough.
Prometh is a great potentiator and on substnces such as codeine and dihydrocodeine wil boost the conversion into morphine. Meperidine of course does not gain this benefit because, sadly, it is not metabolised (of course) into morphine in any way shape or form.