Moclobemide May Help Depression and Post-Partum Blues
Monoamine oxidase inhibitors (MAO-Is) are a type of antidepressant that is often effective for people with anxious depression or comorbid panic attacks, especially when other antidepressants don’t work. This may be because MAO-Is work on all three neurotransmitter systems implicated in depression: dopamine, norepinephrine, and serotonin.
In a recent study presented at the 65th Annual Scientific Convention of the Society of Biological Psychiatry, Julia Sacher et al. found that six weeks of therapeutic doses of the MAO-I moclobemide (at doses of 300 mg twice a day) significantly decreased monoamine oxidase A, as measured by PET scans in brain regions implicated in mood disorders. In a comparison of moclobemide, placebo, and the herbal preparation St. John’s Wort, only moclobemide had a significant effect.
There are various types of MAO-Is, and their different effects are currently being investigated. Moclobemide is an MAO-I that is selective for monoamine oxidase A, and it is currently only available in Canada. Two nonselective MAO-Is, tranylcypromine (Parnate) and phenelzine (Nardil), are available in the US. A selective monoamine oxidase type B (MAO-B) inhibitor, selegiline, is FDA-approved for the treatment of depression as a patch. St. John’s Wort is thought to inhibit monoamine oxidase type A in addition to its other potential antidepressant mechanisms.
Editor’s Note: MAO-Is prevent monoamine oxidase from metabolizing norepinephrine, as it normally would, and the large amounts of norepinephrine that remain when one is treated with an MAO-I can lead to high blood pressure and severe headaches.
The selective monoamine oxidase inhibitors moclobemide and selegiline have fewer cardiovascular side effects than the nonselective MAO-Is tranylcypromine and phenelzine. With the nonselective MAO-Is, it is important to avoid foods that have high levels of tyramine, such as aged cheeses, because tyramine can release norepinephrine.
The MAO-I tranylcypromine has often shown excellent antidepressant effects in bipolar depression, but moclobemide and the selegiline patch have not been widely studied in bipolar depression.
Brain MAO-A Linked to Post-Partum Depression
The Sacher et al. study that moclobemide inhibits MAO-A in human brain takes on added importance when combined with another study by the same research group published in the Archives of General Psychiatry this year, which found that women with post-partum blues have more monoamine oxidase type A in their brains 4 to 6 days following delivery than nonpregnant women do. Because post-partum blues are a risk factor for developing full-blown post-partum depression, these findings raise the possibility that treatment with monoamine oxidase inhibitors may be able to reduce the incidence of post-partum depression.
During the post-partum period, monoamine oxidase type A increases as a result of the drop in circulating estrogens that occurs at this time; estrogens normally suppress MAO-A. This increase in MAO-A leads to the more rapid metabolism of many neurotransmitter monoamines, reducing their levels in blood and brain, thus potentially propelling a subsequent depression. Given the findings of Sacher et al., that clinical treatment with usual doses of the selective monoamine oxidase A inhibitor moclobemide clearly inhibits human MAO-A in brain, drugs such as moclobemide and the selegiline patch deserve further investigation for potential treatment and/or prevention of post-partum depression.
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