Generics Blog|Medical-Care News

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For your elderly nursing home patients who are agitated, a recently approved antipsychotic agent may be an alternative to traditional antipsychotics, according to Ned H. Cassem, MD. Risperidone (Risperdal) has received FDA approval for the treatment of schizophrenia and other psychotic disorders.

“It’s a great help for us, because it helps people to settle down without the bad side effects that have troubled us up to now,” said Dr. Cassem.

He said risperidone’s main advantage, when given at low doses, is its relatively low incidence of parkinsonian side effects and tardive dyskinesia, common adverse effects of conventional antipsychotics. Until now, the only drug to offer this advantage was clozapine, which carried the risk of agranulocytosis, according to Dr. Cassem. Because this is not a significant risk with risperidone, weekly white blood cell monitoring is not required.

Risperidone is the first drug in a new chemical class called ben-zisoxazole derivatives. Although its exact mechanism for inducing fewer extrapyramidal side effects is unknown, the drug’s clinical benefits appear to derive from blockade of both serotonin and dopamine receptors.

For agitation, Dr. Cassem recommends a daily dose of 0.5 to 1 mg given at bedtime, not to exceed 10 mg/d.

Dr. Cassem is associate professor, Harvard Medical School, and chief of psychiatry, Massachusetts General Hospital, Boston.

Source: American College of Physicians 75th Annual Session, Miami Beach, FL

ANTIDEPRESSANT INTERACTIONS

The latest generation of antidepressants, the selective serotonin reuptake inhibitors — fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), sertraline (Zoloft), and nefazodone (Serzone) –seem to have fewer side effects than their predecessors. However, as laboratory studies indicate, many of these newer agents have the potential to do more than elevate mood; they may also affect the metabolism of other drugs. The SSRIs do so by acting on the cytochrome P450 system — a family of approximately 30 closely related enzymes. These enzymes play a vital role in breaking down certain drugs in the liver so that they can be used by and eliminated from the body.

The cytochrome P450 system isn’t completely understood, but researchers have discovered that most of us don’t make all of the enzymes in the system and that our ability to make the enzymes diminishes with age. For that reason, each of us responds to drugs somewhat differently, and we often need to use a trial-and-error approach to find the right medication.

Taking an SSRI can further alter our individual response to other drugs. Each of the SSRIs inhibits one or more of the cytochrome P450 enzymes. As a result, medications that are metabolized by these enzymes — be they antihistamines, analgesics, or other antidepressants — may be absorbed less rapidly and remain in circulation for longer periods in people who are taking SSRIs. In some cases, an SSRI may increase the effectiveness of a second drug, allowing lower doses to be used; in others, an SSRI may cause toxic levels of the other drug to accumulate. For that reason, if you are taking one of the SSRIs it is important to let your clinician know the other medications — prescription and over-the-counter — that you are taking.

The chart below lists the SSRIs and the medications with which they might interact.

POSSIBLE INTERACTIONS AMONG COMMON DRUGS

Prozac, Zoloft: Elavil, Anafranil, Norpramin, Tofranil, Pamelor, Ludiomil, Valium, Xanax, Versed, Halcion, quinidine, Hismanal, Seldane, Lopressor, Inderol, Procardia, Adalat, Clozaril, Haldol, Moban, Triavil, Risperdal, Mellaril, codeine, Percodan, Talwin, Iidocaine, Mevacor, tamoxifen, testosterone, dextromethorphan

Paxil: Elavil, Anafranil, Norpramin, Tofranil, Pamelor, Ludiomil, Lopressor, Haldol, Moban, Triavil, Risperdal, Mellaril, codeine, Percodan, Talwin, dextromethorphan

Luvox: Elavil, Tofranil, Pamelor, Norpramin, Lopressor, Inderol, Clozaril, Haldol, Moban, Triavil, Risperdal, Mellaril, codeine, Percodan, methadone, Talwin, dextromethorphan, tacrine, caffeine, theophylline

Serzone: Norpramin, Xanax, Valium, Versed, Halcion, quinidine, Hismanal, Seldane, Cardizem, Procardia, Adalat, Iidocaine, hydrocortisone, dexamethasone