Large Population-Based Study Confirms Increased Risk of VTE With Antipsychotics
Major Finding: Patients taking antipsychotics had a 32% greater risk of venous thromboembolism, compared with those not on the drugs.
Data Source: A nested case-control study of 115,023 primary care patients in the United Kingdom.
Disclosures: The authors reported that they have no relevant financial relationships.
FROM THE BRITISH MEDICAL JOURNAL
Overall, antipsychotic users had a 32% greater risk of VTE than did nonusers. Among those on antipsychotics, 38% were current users and their increase in risk was 56% compared with 36% for recent users. The risk was not significantly increased for past users. Among current antipsychotic users, 15% had started a new drug within the 3 months prior to the index date. This group of new users showed a greater increase in risk (97%) than did continuing users (29%).
Patients who were prescribed atypical antipsychotic drugs had a greater risk of VTE than did those who were prescribed conventional antipsychotics – 73% compared with 28%. Patients who had received only one prescription in the previous 12 months had a significantly greater risk (32%) than did those receiving none. In addition, those who were prescribed two or more different antipsychotics had a greater risk (99%) than did those who received only one (29%).
The most commonly prescribed drug was prochlorperazine – a high-potency phenothiazine – which also is commonly prescribed for nausea, vomiting, and vertigo. Prochlorperazine was prescribed for 75% of the total number of those on antipsychotics. The other most commonly prescribed drugs were (in order) risperidone, haloperidol, olanzapine, chlorpromazine, trifluoperazine, and quetiapine. Separate odds ratios were estimated for exposure to these drugs, with highest risks for those patients who were prescribed quetiapine, chlorpromazine, and haloperidol, with adjusted odds ratios of 2.81, 1.77, and 2.17, respectively.
Individuals with a diagnosis of dementia were at higher risk than were those with diagnoses of schizophrenia, bipolar disorder, or none of these conditions. There was a more than threefold increase associated with cancer and a roughly 13-fold increase associated with recent surgery or fractures. “Individuals prescribed statins or aspirin in the past 24 months had a lower risk of venous thromboembolism, and those prescribed NSAIDs, oral contraceptives, hormone replacement therapy, tamoxifen, or antimanics had a higher risk,” the authors noted.
The number needed for harm for any antipsychotic use in the past 24 months for patients aged 65 years and older was 1,044; for new users in the past 3 months this number was 344; and for continuing users it was 1,152. The corresponding numbers of excess cases of VTE per 10,000 treated patients were 10, 29, and 9, respectively.
The study authors reported that they have no relevant financial relationships.
