To the Editor:
Tamsulosin hydrochloride, CAS number 106463-17-6, is a selective antagonist for alpha(1A) and alpha(1D) adrenoreceptors that is used in the treatment of benign prostate hyperplasia (BPH) Citation1-3. We report the first case of acute intoxication with tamsulosin hydrochloride.
A 78-yr-old female was admitted following an unintentional overdose of tamsulosin. Late in the evening she had ingested five tablets of tamsulosin (0.4 mg) prescribed for her husband for the treatment of BPH. She mistook the drug for herbal tablets that she usually took for insomnia. The next morning she complained of a headache and dizziness and collapsed while getting up. At the time of admission, the patient was alert, with good verbal response. She had a pulse of 47–50 beats/min and orthostatic hypotension (BP 100/50 mmHg while lying and 60/40 in sitting position). Physical examination was otherwise normal. An electrocardiogam (ECG) showed sinus bradycardia with PQ and QTc intervals 0.2 sec and 0.41 sec, respectively. After 20 h of supportive care the heart rate had risen to 75–80 beats/min and the blood pressure had risen to 150/90 mmHg. The heart rate and blood pressure were stable over the next 10 h and the patient was discharged in a good general condition after 30 h of hospitalization.
Tamsulosin is well tolerated even in risk patients such as those with cardiovascular comorbidity and comedication Citation1Citation3. The most frequent adverse reactions due to tamsulosin overdosage are orthostatic hypotension, tachycardia, dizziness and headache, gastrointestinal complaints, ejaculation disorders, hypersensitivity reactions such as rash and pruritis, and contact dermatitis Citation2Citation4. In our case, bradycardia and hypotonia dominated in the clinical pattern. The mechanism of bradycardia during intoxication with selective antagonist for alpha(1A) and alpha(1D) adrenoreceptors is unknown but a 22-yr-old male who ingested 40 mg of doxazosine showed sinus bradycardia with ST-segment elevation on the ECG Citation5.
Jacek Sein Anand
Zygmunt Chodorowski
Marek Wiśniewski
1st Clinic of Internal Disease and Toxicology
Medical University of Gdańsk, Poland
Head: Zygmunt Chodorowski, M.D., Ph.D.
1st Clinic of Internal Disease and Toxicology
Medical University of Gdańsk, Poland
ul. Dębinki 7, 80-211
Tel./fax. (+ 48 58) 349-28-32
E-mail: [email protected]
References
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- Chapple C R, Wyndaele J J, Nordling J, Boeminhaus F, Ypma A F, Abrams P. Tamsulosin the first prostate-selective-alpha 1A-adrenoreceptor antagonist. A meta-analysis of two randomized, placebo-controlled, multicentre studies in patients with benign prostatic obstruction (symptomatic BPH). European Tamsulosin Study Group. Eur Urol 1996; 29:155–167., [PUBMED], [INFOTRIEVE], [CSA]
- Lijnen L PR, de Graff L. Systemic contact dermatitis from tamsulosin. Contact Dermatitis 2003; 49:50–51., [PUBMED], [INFOTRIEVE], [CSA], [CROSSREF]
- Gokel Y, Dokur M, Paydas S. Doxazosine overdosage. Am J Emerg Med 2000; 18:638–639., [PUBMED], [INFOTRIEVE], [CSA]