Case Report

acute intoxication with terazosin

Abstract

We report a first case of acute intoxication with terazosin in a 75-year-old man presenting with bradycardia and hypoten- sion. The patient received supportive treatment and was discharged with no sequelae 48 hours after the admission. The coexistence of bradycardia and terazosin overdose has never been mentioned in any literature. This case report attempts to exemplify the possibility of this connection.

Terazosin is a postsynaptic ?₁-adrenoceptor antagonist widely used in the treatment of hypertension and benign prostate hyperplasia [1-3]. Experience with acute terazosin intoxication still remains very limited, and documentation of terazosin overdose has never been published. We believe this case of acute intoxication with terazosin presented with bradycardia and hypotension is the first to be reported in the literature.

A 75-year-old man was brought to our emergency department by his family with complaints of headache and dizziness. On the day of admission, he had a quarrel with family. He ingested 60 tablets of 5 mg terazosin with the intention to commit suicide and informed his son about that 2 hours later. The patient had been relatively well except for a 2-year medical history of hypertension and benign prostate hyperplasia with follow-up at our cardiovascular and urology clinic regularly. For the preceding 6 months, he was taking terazosin 5 mg QD, which gave stable blood pressure readings of 126/86 mm Hg and heart rate around 70 beats per minute on his last clinic visit.

On arrival, the patient was orientated and alert. He had an initial temperature of 34.4?C, pulse rate of 42 beats per minute, respiratory rate of 16 breaths per minute, blood pressure of 73/43 mm Hg, and a room air oxygen saturation of 98%. He denied chest discomfort or shortness of breath. Physical examination result was significant only for regular bradycardia with the presence of grade II/VI systolic ejection murmur along the left lower sternal border and apex. The remainder physical examinations were otherwise unremarkable.

A resting electrocardiogram (ECG) showed sinus brady- cardia with heart rate of 42 beats per minute, PR interval of

160 milliseconds, QRS of 80 milliseconds, and a QTc interval of 400 milliseconds. Chest radiography revealed normal heart size without Pulmonary infiltrates. Routine laboratory studies such as complete blood count, blood glucose level, alanine aminotransferase, creatinine, sodium, potassium, calcium, magnesium, creatine kinase-MB, and Troponin I levels were all within normal limits. Results of toxicologic screens including benzodiazepines and barbitu- rates were all negative. The patient denied taking alcohol or other medications.

Based on the history provided and the pill bottle brought by the family, acute terazosin intoxication was impressed. gastric lavage with saline and 80 g of oral activated charcoal was prescribed. A few terazosin pill fragments were found. The patient was also given 500 mL normal saline solution bolus and 0.5 mg of intravenous atropine after which his pulse rose to 50 beats per minute and blood pressure rose to 82/46 mm Hg. By 12 hours after supportive treatment, the patient’s blood pressure rose to 96/60 mm Hg with pulse rate around 56 beats per minute. Twenty-four hours after admission, the patient’s blood pressure rose to 110/68 mm Hg. The ECGs reverted to normal sinus rhythm at a heart rate of 64 beats per minute. Serial cardiac enzyme follow- up yielded negative findings for acute coronary syndrome. Echocardiography revealed mild Mitral regurgitation with an ejection fraction of 76% by M mode. The heart rate and blood pressure were stable in the ensuing 12 hours, and the patient was discharged home with no sequelae 48 hours after the admission. He had a follow-up at our cardiovascular and psychiatric clinic with stable blood pressure of 128/82 mm Hg and heart rate around 72 beats per minute.

Terazosin is a kind of quinazoline derivative ?₁- adrenoceptor antagonist developed for the treatment of Essential hypertension. It lowers blood pressure by selec- tively blocking postsynaptic ?₁-adrenoceptors that result in the relaxation of arteries and reduction of total peripheral resistance [1]. Terazosin is also effective in the treatment of benign prostate hyperplasia by relaxing the smooth muscle of the bladder neck that reduces bladder outlet obstruction [2,3]. Terazosin therapy is claimed to be safe because it causes significant reduction in blood pressure with only little influence on heart rate [1]. The most common adverse effects are dizziness, headache, asthenia, nasal congestion,

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117.e6 Case Report

Postural hypotension, and syncope [1-3]. Current literature has never reported bradycardia as a complication of acute terazosin overdose. To the best of our knowledge, we believe the case we reported is the first.

The Therapeutic dose of terazosin is 1 mg/d initially and is increased gradually to a maximum dose of 20 mg/d. Our patient ingested significantly larger doses (300 mg) than recommended, which caused his intoxication. The exact mechanism of bradycardia after terazosin overdose is not well understood. Although reflex tachycardia is the most common cardiac complication of ?-adrenoceptor antagonist overdose, bradycardia has also been reported [4-6]. Gokel et al [5] reported a 22-year-old man who developed bradycardia and ST-segment elevation on ECG after doxazosin intoxication. He postulated that bradycardia may occur because of (1) the absence of presynaptic ?₂- adrenoceptor blockage that prevents the accelerated release of noradrenaline from nerve endings and (2) blockage of central ?₁-adrenoceptors that cause a blunting of the reflex tachycardia via the baroreceptor mechanism [5]. Being an ?₁-adrenoceptor antagonist with similar properties to doxazosin, terazosin may act with the similar pharmacolo- gic mechanism in causing bradycardia.

In summary, our report is the first case of an acute intoxication with terazosin in the literature. The relationship between bradycardia and terazosin overdose is still not quite fully understood and will require further investigation.

Thus, this case simply provides another presentation of terazosin overdose.

Chen-June Seak MD Chih-Chuan Lin MD

Department of Emergency Medicine Chang Gung Memorial Hospital

Linkou, Taiwan College of Medicine

Chang Gung University, Taoyuan, Taiwan E-mail address: [email protected]

doi:10.1016/j.ajem.2007.08.002

References

1. Dauer AD. Terazosin: an effective once-daily monotherapy for the treatment of hypertension. Am J Med 1986;80:29-34.
2. Mudiyala R, Ahmed A. Effect of terazosin on clinical benign prostatic hyperplasia in older adults. J Am Geriatr Soc 2003;51:424-6.
3. Lepor H, Jones K, Williford W. The mechanism of adverse events associated with terazosin: an analysis of the Veterans Affairs cooperative study. J Urol 2000;163:1134-7.
4. Anand JS, Chodorowski Z, Wisniewski M, et al. Acute intoxication with tamsulosin hydrochloride. Clin Toxicol 2005;43:311.
5. Gokel Y, Dokur M, Paydas S. Doxazosin overdosage. Am J Emerg Med

2000;18:638-9.

1. Ball J. Symptomatic Sinus bradycardia due to prazosin. Lancet 1994; 343:121.