Phase I Metabolism
Definition
Functionalisation reactions (oxidation, reduction, hydrolysis) that introduce or expose a polar group on the drug molecule, mostly catalysed by cytochrome P450 isoenzymes in the hepatic endoplasmic reticulum. Produces metabolites that may be active, inactive or more toxic than the parent.
Related terms
- 6-Monoacetylmorphine (6-MAM)
- A transient diagnostic metabolite of heroin (diacetylmorphine) formed by the rapid hydrolysis of one acetyl group. Half-life is 6 to 25 minutes...
- Benzoylecgonine (BE)
- The major hydrolysis metabolite of cocaine, formed by carboxylesterase action on the methyl ester of cocaine. Half-life is around 6 hours in...
- Phase II Metabolism
- Conjugation reactions (glucuronidation, sulphation, glutathione conjugation, acetylation, methylation, glycine conjugation) that attach a polar endogenous group to the drug or its Phase...
- Post-Mortem Redistribution (PMR)
- The phenomenon where drug and poison concentrations shift between body compartments after death, generally moving out of solid organs back into the...
- Therapeutic, Toxic and Lethal Ranges
- Plasma concentration ranges that guide interpretation, derived from population studies and case reports. They are guidelines, not absolutes. Tolerance, idiosyncratic response, polypharmacy...
- Volume of Distribution (Vd)
- The apparent volume in which a drug is distributed in the body, calculated as dose divided by plasma concentration at time zero....
Explained in
- Drug Metabolism, Distribution and Metabolite IdentificationFunctionalisation reactions (oxidation, reduction, hydrolysis) that introduce or expose a polar group on the drug molecule, mostly catalysed by cytochrome P450...