Ziprasidone chemical structure
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Geodon

Ziprasidone (sold as 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. more...

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It has been approved for acute episodes indicative of bipolar type I. It has not been studied in adolescents or children (under age 10). 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.

Read more at Wikipedia.org


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Geodon for injection - New & Approved
From OB/GYN News, 8/15/02 by Elizabeth Mechcatie

(IM ziprasidone, Pfizer)

An intramuscular formulation of the atypical antipsychotic for treating acute agitation in schizophrenic patients who need an IM antipsychotic for rapid control of agitation. The first atypical antipsychotic to be approved in an IM formulation.

* Recommended Dosage: 10 mg (every 2 hours) to 20 mg (every 4 hours) as needed up to a maximum of 40 mg/day.

* Special Considerations: Contraindicated in patients with QTc prolongation, due to dose-related effect on prolongation of the QTc interval of the electrocardiogram.

In studies of oral Geodon, some patients had QTc increases, which can lead to torsades de pointes, but there were no cases of arrhythmias or sudden unexplained deaths. Modest increases in the mean QTc interval also were seen within 2 hours of the intramuscular dose, Pfizer reported at an FDA advisory panel meeting in 2001. Coadministration with oral Geodon not recommended.

* Comment: This approval "is a significant advancement in treatment options for patients who are suffering with acute agitation," said Dr. Daniel Casey, chief of psychiatric research and psychopharmacology at Veterans Affairs Medical Center, Portland, Ore. It "will be used in a wide range of clinical situations where significant agitation is the immediate clinical concern," he predicted.

IM Geodon has the advantage of having "equal or better efficacy" than the shortacting antipsychotics used for decades in treating acute agitation in patients with a wide range of diagnoses, but it has far fewer side effects, particularly extrapyramidal symptoms, Dr. Casey noted. Geodon is nor associated with dysphoria, a common side effect of typical antipsychotics, and does not pose a risk of dependence, an issue with intramuscular benzodiazepines, he added.

QTc prolongation with Geodon is "very well characterized, and there are no data to suggest that it correlates with any clinical consequences," Dr. Casey said. Among more than 200,000 patients who have been treated with oral Geodon, there have been no reports of torsades, other arrhytmias, or increased rates of sudden unexpected deaths. There is no evidence that the IM formulation will be different, he said.

Dr. Casey was a consultant to Pfizer in the analysis of the clinical trial data.

COPYRIGHT 2002 International Medical News Group
COPYRIGHT 2002 Gale Group

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