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Disadvantages of Olanzapine Offset by Its Ability to Reduce Hospital Admissions: Presented at CPA

By Alison Palkhivala

MONTREAL, CANADA -- November 20, 2007 -- Adverse effects that have been associated with olanzapine (Zyprexa(R)) -- such as weight gain, high cost, and increased incidence of type 2 diabetes -- may be offset by the drug's ability to reduce the risk of hospitalisation, according to a benefit-risk-cost analysis.

"The important thing for use was how people are interpreting the CATIE [Clinical Antipsychotic Trials of Intervention Effectiveness] study," Senior Author James L. Karagianis, MD, Clinical Research Physician, Eli Lily Canada, Inc., said in an interview. "It seems to mean different things for different people. One of the ways of making it more relevant to clinicians is looking at number needed to treat [NNT] and number needed to harm [NNH]."

"The two outcomes that we thought were the most relevant to the clinician's decision to prescribe was the benefit of avoiding a hospitalisation and the hazard or risk of weight gain more than 7%," said Dr. Karagianis. "We often hear of olanzapine being associated with weight gain, so 'number needed to harm' can help us see how much of a problem that is compared to the other drugs, while the number needed to treat can help figure out how frequently you can avoid a hospitalisation event by using olanzapine compared to some of the other drugs."

Dr. Karagianis and colleagues used data from CATIE to obtain the NNT to avoid one hospitalisation as well as the NNH for weight gain of 7% with use of olanzapine instead of quetiapine, perphenazine, ziprasidone, or risperidone. He presented the findings here on November 16 at the 57th Annual Conference of the Canadian Psychiatric Association (CPA).

Relative to olanzapine, the NNT for hospitalisation was 4.60 for perphenazine, 2.70 for quetiapine, 6.20 for risperidone, and 3.60 for ziprasidone. The NNH for weight gain of at least 7%, again in relation to olanzapine, was -5.55 for perphenazine, -7.19 for quetiapine, -6.26 for risperidone, and -4.44 for ziprasidone.

"By choosing olanzapine instead of quetiapine, for example, you have to treat 2.7 people with olanzapine instead of quetiapine to avoid one hospitalisation event," explained Dr. Karagianis. "On the negative side, you would have to treat 7.19 people with olanzapine instead of quetiapine to expect an additional person gaining 7% or more of their body weight.

"The question is, is that a reasonable tradeoff to make? Only a patient and doctor can make that decision for themselves, but if you assume those [outcomes] are of equal value, you can calculate what's called a 'likelihood of being helped or harmed' ratio," Dr. Karagianis said. "It's basically the number needed to harm for the bad event divided by the number needed to treat for the good event. And in every case, when you compare olanzapine to each of the comparators, you get a relationship of more than one, which suggests that you have a greater probability of being benefited by the good thing than you have of being harmed by the bad thing."

Using Canadian data, the investigators also performed a cost analysis in which the cost of the drug was offset by the degree to which it is expected to reduce the risk of a hospital stay, which itself was estimated to cost an average of $10,415. Using that calculation, olanzapine is actually less costly than quetiapine. Calculating the costs of antidiabetic drugs that might need to be prescribed as a result of olanzapine use results in an additional $55 to $74 needing to be spent per 100 patients treated with olanzapine instead of perphenazine, quetiapine, or risperidone.

When selecting a therapy, "you always have to think about the risks and the benefits together," concluded Dr. Karagianis.

The study was conducted by Eli Lilly, Canada, Inc.


[Presentation title: Benefit-Risk-Cost Assessment of the Use of Olanzapine in the Treatment of Schizophrenia: A Canadian Context for the Interpretation of CATIE. Poster P16]

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