Psychosomatics 47:73-74, February 2006
doi: 10.1176/appi.psy.47.1.73
© 2006 Academy of Psychosomatic Medicine
Oxcarbazepine-Induced Thrombocytopenia
Jamal Mahmud, M.D.,
Maju Mathews, M.D.,
Sunil Verma, M.D., and
Biju Basil, M.D.
Received February 2, 2005; accepted March 9, 2005. From the Dept. of Psychiatry, Drexel Univ. College of Medicine, Philadelphia, PA. Address correspondence and reprint requests to Dr. Jamal Mahmud. e-mail: jamalmfr{at}yahoo.com
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INTRODUCTION
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Oxcarbazepine is an antiepileptic drug indicated mainly for partial seizures, neuropathic pain, and trigeminal neuralgia. It is also used as a mood-stabilizer in bipolar disorder.1 Oxcarbazepine has a chemical structure similar to carbamazepine; i.e., it is a keto-derivative, but it differs in its metabolism.2 It is rapidly reduced to its active metabolite MHD (monohydroxy derivative). The bioavailability of its oral formulation is high, above 95%. It is rapidly absorbed, with peak plasma concentrations achieved in 1–3 hours. It has almost-absent or minimal enzyme-inducing effects.
Thrombocytopenia is the decrease in platelet count to less than 150,000/µl (normal range: 150,000/µl–400,000/µl). Thrombocytopenia can be caused by a number of drugs, including anticonvulsants, antihypertensives, heparin, procainamide, sulfonamides, thiazide diuretics, etc.
Thrombocytopenia is not a reported side effect of oxcarbazepine in adults. The package insert of oxcarbazepine mentions that there is a possibility of thrombocytopenia in children previously treated with antiepileptic drugs. Here, we describe the first-ever case of decrease in the number of platelets as a result of oxcarbazepine use.
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Case Report
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A 63-year-old Asian American woman with history of depression with psychotic features and multiple past psychiatric hospitalizations was brought to the hospital for increasingly disorganized behavior and paranoid ideation. She was on clozapine 275 mg but had become noncompliant with blood testing, leading to discontinuation of the clozapine, thus requiring hospitalization.
On the day of admission, the patient was disheveled, withdrawn, selectively mute, guarded, paranoid, and was responding to auditory hallucinations. She refused initial lab work and ECG, but the results of lab work done later were within normal limits, at 300,000/µL. The patient was initially started on nortriptyline and risperidone. She did not show any response, and she became more withdrawn and isolated. She was not interacting with her peers, and she became agitated, which necessitated the addition of lorazepam to the regimen.
Because there was no positive response, the nortriptyline and risperidone were stopped; she was started on aripiprazole, and the antidepressant medication was changed to venlafaxine.
She continued to be withdrawn and isolated, and did not participate in activities, even after an adequate trial with the new medications. Oxcarbazepine 300 mg bid was then added as adjunctive therapy to her ongoing treatment with venlaflaxine and aripiprazole. The patient showed a good response to this, and there was an improvement in her mood and energy levels. She became more interactive in groups and daily activities on the unit. After being on oxcarbazepine for some days, she developed a low-grade fever, and complete blood count (CBC) with differential showed her platelet count to be 208,000. The internal-medicine consult team evaluated the patient for ITP (idiopathic thrombocytopenic purpura), but there was no other clinical evidence to suggest this condition. The partial thromboplastin time, prothrombin time, and international normalized ratio were within normal limits. The CBC monitoring was done every day, and the platelet count continued to fall—to 110,000 by the seventh day and 18,000 by the 10th day of treatment. Because no other medications had been introduced during this period, we concluded that this decrease in platelets was secondary to oxcarbazepine, and it was discontinued. Platelet monitoring on the fourth day after discontinuation of oxcarbazepine revealed a count of 250,000, and, by the seventh day, it was within normal limits.
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Discussion
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A cause-and-effect relationship between oxcarbazepine and thrombocytopenia is being postulated because a previously normal blood profile became abnormal without any other change in pharmacotherapy or medical causes. This abnormality also corrected itself when the offending agent was discontinued.
In this case report, we have tried to convey the possibility that thrombocytopenia may result from therapy with oxcarbazepine. Physicians prescribing this agent should be aware of this side effect, and we advise screening with hemograms and blood-profile monitoring.
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REFERENCES
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- Ghaemi SN, Berv DA, Klugman J, et al: Oxcarbazepine treatment of bipolar disorder. J Clin Psychiatry 2003; 64:943–945[Medline]
- May TW, Korn-Merker E, Rambeck B: Clinical pharmacokinetics of oxcarbazepine. Clin Pharmacokinetics 2003; 42:1023–1042[CrossRef][Medline]
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