Pharmacology Notes

Maprotiline and mirtazapine are absorbed from the GI tract, distributed widely in the body, metabolized by the liver, and excreted by the kidneys.

Bupropion is well absorbed from the GI tract and metabolized by the liver. Its metabolites are excreted by the kidneys. It appears to be highly bound to plasma proteins.

Venlafaxine is rapidly absorbed after oral administration, partially bound to plasma proteins, metabolized in the liver, and excreted in urine.

Trazodone is well absorbed from the GI tract, distributed widely in the body, and metabolized by the liver. About 75% is excreted in urine; the remainder is excreted in stool.

Nefazodone is rapidly and completely absorbed but, because of extensive metabolism, only about 20% of the drug is available. The drug is almost completely bound to plasma proteins and is excreted in urine.

Maprotiline and mirtazapine probably increase the amount of norepinephrine, serotonin, or both in the CNS by blocking their reuptake by presynaptic neurons (nerve terminals).

Bupropion was once thought to inhibit the reuptake of the neurotransmitter dopamine; however, it more likely acts on nonadrenergic receptors.

Venlafaxine is thought to potentiate neurotransmitter activity in the CNS by inhibiting the neural reuptake of serotonin and norepinephrine.

Trazodone, although its action is unknown, is thought to exert antidepressant effects by inhibiting the reuptake of norepinephrine and serotonin in the presynaptic neurons.

Nefazodone’s action isn’t precisely defined. It inhibits neuronal uptake of serotonin and norepinephrine. It’s also a serotonin antagonist, which explains its effectiveness in treating anxiety.

Maprotiline and mirtazapine interact with CNS depressants to cause an additive effect.

Bupropion combined with levodopa, phenothiazines, or TCAs increases the risk of adverse reactions, including seizures.

Trazodone may increase serum levels of digoxin and phenytoin. Its use with antihypertensive agents may increase hypotensive effects. CNS depression may be enhanced if trazodone is administered with other CNS depressants.

Nefazodone may increase the digoxin level if administered with digoxin. It increases CNS depression when combined with CNS depressants.