Pharma gyan Pandit

Biotransformation

Biotransformation of drugs is the process of metabolizing the parent drug compound and occurs mainly in the liver (hence the term hepatic metabolism) to different compounds called metabolites. The drug metabolite may have decreased, increased or undergone no change in pharmacological activity compared to the parent drug. It may also have a different activity. Some drugs are what are termed pro-drugs – that is the drug itself is pharmacologically inactive until it is metabolized by the liver to its active form. A good example is codeine, which is metabolized to morphine by the body. The metabolite is more polar (i.e. chemically charged) than the parent drug and therefore is more readily excreted by the kidney. Drug metabolism can influence dose and frequency of dosing. Drugs which are metabolized quickly have a short duration of action and need to be administered more often (two, three or four times daily). Drugs which are metabolized slowly can have a longer duration of action and may only need to be given on a once-daily basis.