A patient’s weight affects drug concentrations in the blood due to an increase in volume into which the drug is distributed.
A higher proportion of body fat increases the amount of lipid-soluble, slowly metabolized drugs that can be stored in these tissues.
CYP1A2 and CYP2E1 are more active in men, whereas CYP3A4 and CYP2D6 have been shown to be more active in women. Drugs metabolized by CYP1A2, such as clomipramine, clozapine, olanzapine, paracetamol, and theophylline will be deactivated more rapidly in men. Drugs metabolized by CYP2D6, such as codeine, fluoxetine, hydrocodone, metoprolol, paroxetine, sertraline, haloperidol, desipramine, and imipramine will be deactivated more rapidly in women.
UDP-glucuronyl transferases, sulfotransferases, and methyl transferases are more active in men. Drugs conjugated by these enzymes will be deactivated more rapidly in men.
Hepatic blood flow is lower in women. Therefore biotransformation in the liver will be slower for women than men.