Secondary pharmacological implications of metabolism

Metabolites may be either pharmacologically inactive or active. Active metabolites may exhibit a similar activity to the drug or a different activity or be toxic (Table 9.1). In addition, they may exhibit different side effects. 

Drug metabolism can occur in all tissues and most biological fluids. However, the widest range of metabolic reactions occurs in the liver. A more substrate-selective range of metabolic processes takes place in the kidney, lungs, brain, placenta and other tissues. 

Inactive Routes that result in the formation of inactive metabolites are often referred to as 

The metabolite may exhibit either a different potency or duration of action or both to the original drug. 

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