Always looking for novel ways to treat bipolar disorder, researchers have turned to an old standby for Tylenol overdose: n-acetyl cysteine (NAC). Among other causes, mood disorders may be a result of oxidative or metabolic imbalances in the brain caused by low levels of the biochemical glutathoine. NAC works to restore these imbalances, which are possibly at the root bipolar depression, by working as an antioxidant.
While its absolute efficacy has not been proven, one randomized controlled trial showed statistically significant improvement in overall depressive symptoms in bipolar patients on long-term therapy with 1g of NAC taken twice daily in a capsule formulation.1 This is a non-FDA approved version, which is only available as a nutritional supplement. Unlike the liquid and injection available by prescription, only a small percentage of the capsule formulation is active because it is broken down so quickly by the body.2
The study results also have to be interpreted with caution because the trial only involved 75 patients. Another limitation is that the time to next mood episode was the same regardless of whether the patient was taking NAC or placebo. On the positive side, the trial took place over a 24-week period and showed moderate improvement in symptoms. Despite the lack of published evidence, some U.S. psychiatrists are finding a useful place for NAC in clinical practice.
Although NAC is typically described as well tolerated, the side effects may be appreciable. Nausea, abdominal pain, vomiting, constipation, and diarrhea are common with oral treatment.
Recommendation: Because of its sparse efficacy data and at times noxious side effects, this nutritional supplement has a limited place in therapy.