Reversible Inhibitors of Monoamine Oxidase (RIMAs)

RIMAs are a new generation of MAOIs developed specifically to be safer than their older counterparts. Unlike the older MAOIs, RIMAs only inhibit the enzyme, monoamine oxidase type A, not monoamine oxidase type B, as do the older MAOIs. By preserving the activity of brain chemicals involved in depression, RIMAs make these chemicals more available for normal brain function. RIMAs do not, however, prevent the breakdown of tyramine in food, so that tyramine levels do not accumulate in the body to any dangerous degree.

RIMAs do not hang on irreversibly to monoamine oxidase enzyme either - making it much less risky for people who may need to switch to a different antidepressant within a few days of stopping the drug. RIMAs appear to be almost as effective in the treatment of depression as are the MAOIs, they do not affect sleep, are non-sedating and non-agitating.

They may, however, cause insomnia if taken too late in the day, and gastrointestinal discomfort as well as headache and dry mouth have been reported with RIMA use as well.

The only currently available RIMA in Canada is moclobemide (Manerix).

How to minimize side effects when taking Manerix   

• Get up slowly if you are lying or sitting down to minimize dizziness.
• Use talcum powder if sweating occurs.
• Chew sugarless gum or suck on sugarless candy to increase salivation if dry mouth occurs. Frequent tooth brushing helps too.
• Increase dietary fiber, exercise more often and drink lots of fluids if constipation occurs.
• Try reading under a bright light and hold book at a distance or wearing reading glasses if blurred vision occurs. Prescribed eye drops may also help.
• Take the medication after meals to minimize potential food interactions.
• Avoid excessive amounts of tyramine-containing foods, including aged cheese and sauerkraut.
• Take no other drugs without first consulting your doctor or pharmacist and avoid all products containing dextromethorphan.
• If you miss your dose by more than 5 hours, skip the missed dose and continue with your next scheduled dose.
• Don't stop taking the medication abruptly, otherwise headache, irritability or agitation may occur.

There are a number of new antidepressants that have properties that are often special to that particular agent. These medications include nefazodone (Serzone), venlafaxine (Effexor) and bupropion (Wellbutrin).

Serzone blocks the reuptake pump from removing serotonin in the synapse - just as the SSRIs do. At the same time, it also blocks certain sites on cells which normally receive messages from transmitting cells. This additional blocking action is thought to enhance its antidepressant effects. Blocking some of serotonin's activity in the receiving cell appears to decrease side effects associated with the SSRIs, especially sexual side effects, insomnia and agitation. However, Serzone does cause drowsiness, stomach upset and headache in some people, as do other SSRIs.

Effexor similarly affects the reuptake pump but instead of preventing just the depletion of serotonin in the gap between cells, it prevents the depletion of another brain chemical, norepinephrine, which is also implicated in depression and anxiety. Stomach upset (mainly nausea) appears to be the most common side effect reported with Effexor use, but headache, somnolence, dry mouth and dizziness have also been noted.

Wellbutrin in turn blocks the removal of another important brain chemical, dopamine, as well as norepinephrine, from the gap between transmitting and receiving neurons, the net effect of which is to alleviate depression. Reported side effects with Wellbutrin include restlessness, agitation, insomnia, tremor, headache and, in excessively high doses (although rarely) seizures. On the plus side for many depressed patients, Wellbutrin does not cause weight gain and about one-quarter of patients who take the medication report weight loss. Wellbutrin is also not associated with loss of sexual desire as are some of the SSRIs, nor is orgasmic or erectile function impaired. Hence, if sexual side effects from other antidepressant medications prove troublesome, it may be possible to switch to a different medication such as Serzone or Wellbutrin to lessen these effects.

How to minimize side effects associated with the newer cyclic antidepressants   

• Avoid taking Serzone with grapefruit juice as blood levels of the drug may increase.
• Use analgesics if headache persists with Effexor.
• Take Effexor with food if nausea occurs.
• Chew sugarless gum, or use sugarless candy to increase salivation if dry mouth occurs with any of the medications. Frequent tooth-brushing helps too.
• Use talcum powder if sweating occurs.
• Don't stop Effexor, Serzone or Wellbutrin abruptly, otherwise withdrawal symptoms may occur including muscle aches, dizziness, headache, nausea, chills and diarrhea.

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