Yes, magnesium definitely affects anti-anxiety/depression medications. Magnesium has been shown to treat depression, anxiety, etc., at least as well or better than prescription medications used for those purposes. What the abstract at the following link appears to say is that in general, medications in that class tend to boost the availability of magnesium in red blood cells (erythrocytes).
Interactions between magnesium and psychotropic drugs.Abstract
Psychotropic drugs (antidepressants, antimanic drugs, antipsychotics, analgesic opioids, and others) are among the most frequently used medicines. Between these drugs and magnesium there are pharmacokinetic and pharmacodynamic interactions. Erythrocyte magnesium is decreased in patients with severe major depression (MD) vs normal subjects (44 +/- 2.7 mg/L in MD group vs 59.1 +/- 3.2 mg/L in control group, p < 0.01). Therapy with sertraline, 150 mg/day p.o. -21 days or with amitryptiline 3 x 25 mg/day p.o. 28 days increases significantly erythrocyte concentration of magnesium (56.9 +/- 5.22 mg/L after sertraline vs 44 +/- 2.7 mg/L before sertraline, p < 0.01). In patients with acute paranoid schizophrenia, erythrocyte magnesium concentration is decreased vs healthy subjects. Haloperidol, 8 mg/day, p.o. for 21 days or risperidone, 6 mg/day p.o. for 21 days have increased significantly erythrocyte magnesium concentration (46.21 +/- 3.1 mg/L before haloperidol and 54.6 +/- 2.7 mg/L after haloperidol, p < 0.05). Antimanic drugs (mood stabilizers) as carbamazepine, 600 mg/day, p.o., 4 weeks and sodium valproate, 900 mg/day p.o., 4 weeks, increased significantly magnesium in patients with bipolar disorder type I. Increased magnesium status positively correlated with enhancement of the clinical state. The existent data sustain the idea that an increase of erythrocyte magnesium is involved in the mechanism of action of some psychotropic drugs. Magnesium supply decreased the intensity of morphine-induced physical drug dependence. In heroin addicts, the plasma magnesium concentration is decreased.
IOW, the relative timing of when you take those medications and when you take magnesium may matter, even though the article only analyzed and reported on a long-term effect. For all we know, there might be a huge short-term effect. Do you see what I'm saying? The drugs might be boosting magnesium levels in RBCs while robbing magnesium from other cells.
IOW those drugs work by artificially boosting your RBC magnesium level while robbing magnesium from everywhere else. This can make it appear that your magnesium level is fine, when it is not. But if your serum magnesium level is tested, it will be low because the drugs move it to your RBCs. IOW, IMO the medications are causing your symptoms.
Are you taking any B-6? If you happen to be B-6 deficient your ability to absorb magnesium will be compromised. But on the other hand, B-6 aids in the production of tryptophan, which of course is needed for the production of serotonin. So high doses of B-6 might cause drowsiness.
Tex