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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

 Glucuronide formation is the most common phase II reaction.

 Sometimes, the parent drug may undergo phase II conjugation directly.

 In some cases, a drug may undergo a series of consecutive reactions resulting in the
formation of dozens of metabolites.

Examples: conjugation of salicylic acid with glycine to form salicyluric acid OR

glucuronic acid to form salicylglucuronide.

Factors affecting drug metabolism

1. Species
2. Age
3. Sex and hormones

4. Disease state
5. Drug- drug interactions

Enzyme Induction

• Some drugs and chemicals induce synthesis of metabolizing enzymes so that they will

increase rate of metabolism of another drug and as a consequence, the half life of the

latter will be shorter and the dose must be increased. These drugs are called enzyme

inducers.

• As a result, these drugs may decrease bioavailability of other administered drugs that

are metabolized by these enzymes.

 For example, phenobarbital induces the CYP
450
 So if a patient who routinely ingest barbiturates or tranquilizers and who

must, for medical reasons, be treated with warfarin or dicumarol (oral

anticoagulants).

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