Biotransformation Pathways

The most important biotransformation pathways of drugs are:

1. decomposition and combustion to CO₂ and H₂O (example: ethanol),

2. degradation by decarboxylation or deamination (elimination of COO- and NH2-),

3. oxidation or reduction (example: barbiturates),

4. spontaneous or enzymatic hydrolysis (water separation).

The biotransformation pathways run independently of whether the metabolites formed are ineffective, effective, harmless or harmful to the organism. Biotransformation can therefore lead to detoxification if the metabolite is more non-toxic than the original substance, or to poisoning if the metabolite becomes more toxic.