Question

make up a mapping of the metabolism of the following opioids: morphine,hydrocodone,oxycodone,fentanyl,buprenorphine,codeine, and methadone.

Answer 1

The aim of Drug metabolism is ultimately to make a drug hydrophilic to facilitate its excretion in the urine.

Opioid metabolism takes mainly  in the liver by the production of various enzymes.
There are 2 forms of metabolism: phase 1 metabolism (modification reactions) and phase 2 metabolism (conjugation reactions).
Phase 1 metabolism typically subjects the drug to oxida tion or hydrolysis. This stage is involved by cytochrome P450 (CYP) enzymes.The cytochrome enzymes facilitate reactions like Dealkykation of nitrogen,sulphur snd oxygen etc,aromatic, aliphatic, or N-hydroxylation; N-oxidation; sulfoxidation; deamination; and dehalogenation.

Phase 2 metabolism conjugates the drug to hydrophilic substances, such as glucuronic acid, sulfate, glycine, or glutathione.
The important reaction of phase 2 is glucuronidation.

Opioid	phase 1	phase2	extra
Morphine	none	glucuronidation via UGT2B7
Hydrocodone	CYP2D6	NONE	Hydromorphone is a metabolite of hydrocodone,It undergoes phase 2 rexn
Oxycodone	CYP3A4 CYP2D6	None	oxycodone produces oxymorphone which undergoes further metabolism
Fentanyl	CYP3A4	none
buprenorphine	CYP3A4		Buprenorphine and norbuprenorphine Are excreted via urine
codeine	CYP2D6

methadone.

CYP3A4 CYP2B6 CYP2C8 CYP2D6 CYP2D6 CYP2C9

NONE.