- 23 Apr 2009
Of all the classes of antidepressants, the tricyclic antidepressants, or TCAs, have been studied most. (“Tricyclic” refers to the drug’s three-ring chemical structure.) The TCAs shown to work best are desipramine, imipramine, and amitriptyline. All of these products have some troublesome side effects – sedation, dry mouth, lowered blood pressure. Because it has the lowest incidence of side effects, desipramine is usually my first choice for treatment if I am using a tricyclic antidepressant. If a patient has trouble sleeping, I will consider prescribing a product that is more sedating, such as imipramine or amitriptyline.
Of course, because of her purging, a bulimic patient may have trouble keeping anything in her stomach. Medicine won’t do any good if it doesn’t get absorbed. I therefore ask my patients to take their medication just before bedtime, so the drug has time to work.
Sensible practice means giving the lowest dose of medication that still has a chance of producing benefit. Doing so minimizes the risk of side effects. If the patient doesn’t seem to be responding, I gradually increase the dosage. We usually see results within a week or two, but, as in treatment for depression, an adequate trial of these medications often needs a good six weeks.
During the course of therapy it’s necessary to monitor the levels of the medication in the patient’s body. We do so by analyzing blood samples. This step is important because different people metabolize medications at different rates. Two people on the same dosage regimen may show very different plasma levels, and may thus have completely different responses to the medicine. We try to achieve the same plasma levels in bulimics as we do in depressed patients who use the medication.
Getting the right concentration of the drug can mean the difference between therapeutic success and failure. One study showed that a group of patients with a plasma level of desipramine that was below the therapeutic range noticed no improvement in their bulimia. But when the concentration was raised, four out of six patients stopped bingeing.
Some patients incorrectly think that “if a little medication works, then taking more should work even better.” Nortriptyline (another tricyclic), for example, has what we call a “therapeutic window.” This means there are both minimum and maximum levels of concentration that will provide benefits. Above or below those levels, the drug loses its effectiveness.
I also discuss the possible side effects with my patients before I write the prescription. Doing so helps prepare them for any problem they may have with the medication. This in turn improves compliance. If the patient is suicidal or psychotic, or if she abuses drugs or alcohol, antidepressants must be used with extreme caution.
As I’ve said, medications are just part of an overall treatment plan. Prescribing antidepressants without setting up a solid psychotherapeutic relationship with the patient may hurt her chances of getting better.
*61/35/5*
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