Ziprasidone chemical structure
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Ziprasidone

Ziprasidone (Geodon®) was the fifth atypical antipsychotic to gain FDA approval. Ziprasidone is FDA approved for the treatment of schizophrenia, and the intramuscular injection form of ziprasidone is approved for acute agitation in schizophrenic patients. Clinical trials were conducted in acute cases of mania. Long-term trials have not been conducted for acute bipolar symptoms. Any "hypersensitivity to the product" -- including any of the adverse events noted during clinical trials-- should be grounds for discontinuance. It has been approved for acute episodes indicative of bipolar type I. It has not been studied in adolescents or children (under age 10). more...

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Such a trial has been ordered by the FDA as one condition during the approval process. The brand name (Geodon®) has been suggested to bring to mind the phrase 'down (don) to earth (geo)' referring to the goals of medication.

Pharmacology

Ziprasidone has a high affinity for dopamine, serotonin, and alpha-adrenergic receptors and a medium affinity for histaminic receptors. Ziprasidone is somewhat unique among the "atypicals" in that it also displays some inhibition of synaptic reuptake of serotonin and norepinephrine, although the clinical significance of this is unknown. The mechanism of action of ziprasidone is unknown. However it is theorized that its antipsychotic activity is mediated primarily by antagonism at dopamine receptors, specifically D2. Serotonin antagonism may also play a role in the effectiveness of ziprasidone, but the significance of 5-HT2A antagonism is debated among researchers. Antagonism at histaminic and alpha adrenergic receptors likely explains some of the side effects of ziprasidone, such as sedation and orthostasis.

Pharmacokinetics

The systemic bioavailability of ziprasidone administered intramuscularly is 100%, or 60%, administered orally with food. After a single dose intramuscular administration, the peak serum concentration typically occurs at about 60 minutes after the dose is administered, or earlier. Steady state plasma concentrations are achieved within one to three days. The mean half-life (T 1/2) ranges from two to five hours. Exposure increases in a dose-related manner and following three days of intramuscular dosing, little accumulation is observed.

Metabolism

Ziprasidone is hepatically metabolized by aldehyde reductase. Minor metabolism occurs via cytochrome P450 3A4. Medication that induce (e.g carbamazepine) or inhibit (e.g. ketoconazole) CYP3A4 have been shown to decrease and increase, respectively, blood levels of ziprasidone. There are no known induces or inhibitors of aldehyde reductase.

Adverse Events

Ziprasidone may increase the QTc interval in some patients and may increase the risk of a type of heart arrythmia known as torsades de pointes. Ziprasidone should be used cautiously in patients taking other medications likely to interact with ziprasidone or increase the QTc interval.

Adverse events reported for ziprasidone include sedation, insomnia, orthostasis, akathisia and other permanent extrapyramidal side-effects such as tardive dyskinesia. Rarely, temporary speech disorders may result.

The medication can cause any conceivable side effect. See the FDA label for more information.

Recently, the FDA required the manufacturers of all atypical antipsychotics to include a warning about the risk of hyperglycemia and Type II diabetes with atypical antipsychotics. Some evidence suggests that ziprasidone may not be as bad as some of the other atypical antipsychotics at causing insulin resistance and weight gain. In fact, in a trial of long term therapy with ziprasidone, overweight patients (BMI>27) actually had a mean weight loss overall. Ziprasidone, though, is not a weight loss drug. The weight loss reflected in this study on ziprsidone was really reflective of patients who had gained weight on other antipsychotics who were now trending back toward their baseline.

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Meds alert: old schizophrenia drug stands up to new ones
From Science News, 9/24/05 by B. Bower

A class of recently developed medications for schizophrenia has rapidly become psychiatrists' treatment of choice. Small, pharmaceutical company-funded trials had suggested that the drugs are safer and more effective than a generation of antipsychotic substances that has been used since the 1950s.

A new federally funded study of unprecedented size and length calls into question that conclusion. One of the older medications alleviates schizophrenia symptoms about as well as three of the newer, so-called atypical antipsychotics do, say psychiatrist Jeffrey A. Lieberman of Columbia University and his colleagues.

A fourth atypical antipsychotic, olanzapine, yielded slightly more reduction in symptoms than the other drugs did. However, 9 percent of those receiving olanzapine experienced substantial weight gain and metabolic disturbances that can cause diabetes and shorten life, more than twice the proportion for any other drug in the study.

Two-thirds of patients taking olanzapine stopped using it before the 18-month study ended, but three-quarters of participants randomly assigned to any of the other four drugs halted treatment before the study ended. Patients typically stopped using a drug because of lack of improvement or unacceptable side effects.

Schizophrenia patients typically try several antipsychotics before settling on one. "There's no question that atypical antipsychotics work, but they don't fulfill all expectations," says Lieberman.

Atypical antipsychotics cost up to 10 times as much as the older drugs do. Schizophrenia, which affects roughly 1 in 100 people around the world, is a chronic illness that includes hallucinations, delusions, confused thinking, and severe apathy. Antipsychotic medications primarily quell hallucinations and delusions.

Lieberman's team studied 1,493 patients, 18 to 65 years old, who have schizophrenia. These volunteers were already receiving an antipsychotic medication and various types of psychosocial treatment at any of 57 clinical sites in the United States.

Initial results from the project, which ran from 2001 through 2004, appear in the Sept. 22 New England Journal of Medicine.

Participants began treatment with a new drug, randomly chosen from five medications. The four atypical antipsychotics were olanzapine, quetiapine, risperidone, and ziprasidone; the older drug was perphenazine.

The researchers were surprised to find that muscle rigidity, tremors, and other movement disorders that psychiatrists had primarily associated with older drugs occurred at the same low rate with all five medications tested. The most-common side effects for the drugs included sleep problems, constipation, and decreased sex drive.

Lieberman's data dovetail with earlier U.S. evidence (SN: 2/9/02, p. 83) and with a recent clinical study in England, described at a schizophrenia conference in April. In the latter test, 250 patients with schizophrenia exhibited comparable improvement over 1 year, regardless of whether they had been randomly assigned to receive an atypical antipsychotic or an older drug.

"These results remind us that some people do very well on cheap and cheerful first-generation drugs," says psychiatrist Peter B. Jones of the University of Cambridge in England, who directed the British study.

The new studies "support the view that we have a big problem with all [antipsychotic] drugs," remarks psychiatrist William T. Carpenter Jr. of the University of Maryland School of Medicine in Baltimore. Drug companies still need to develop antipsychotic drugs that ease thinking disturbances and apathy, which play crucial disabling roles in schizophrenia, he says.

Olanzapine-induced weight gain and metabolic changes may be especially dangerous, Carpenter notes, because patients with schizophrenia typically smoke, rarely exercise, and eat poorly. "That scares the hell out of me," he says.

COPYRIGHT 2005 Science Service, Inc.
COPYRIGHT 2005 Gale Group

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