Atenolol Massive Ingestion without Poisoning

• Published in: Clinical toxicology (Philadelphia, Pa.) Vol. 46; no. 5; p. 364
• Main Authors: Bigi, S, Petrolini, V, Papa, P, Rolandi, L, Sica, C, Locatelli, C
• Format: Journal Article
• Language: English
• Published: 01.06.2008
• ISSN: 1556-3650

At therapeutic doses, atenolol is a selective beta-1-receptor-blocker without intrinsic agonist activity and membrane stabilizing activity, and with low lipid solubility. It's half-life is 5-9 hours and the therapeutic blood concentration range is 0.2-1 micrograms/ml. Severe hemodynamic and respiratory alterations have been described with atenolol blood levels from 5.6 up to 250 micrograms/ml (1,2). Objective: To describe and discuss a case of massive atenolol overdose documented by laboratory analysis in which the patient remained asymptomatic. Case report: A 43 year-old woman (60 kg bw) was brought to the emergency department 12 hours after ingestion of an estimated amount of 5-10 g of atenolol (assumed not to be usual therapy), promazine 100 mg, lorazepam 10 mg and clonazepam 25 mg. At admission the woman was awake and oriented with no signs of respiratory failure nor bronchial obstruction; the ECG was normal, HR 72 bpm and BP 90/60 mmHg; blood sugar was 92 mg/dl. Monitoring of cardiac parameters was started and gastric decontamination was performed in case of a more recent ingestion. At admission atenolol blood level was 42 micrograms/ml. During the following hours the patient remained asymptomatic with HR 70 bpm and a SBP ranging between 100 and 110 mmHg. No antidotal treatment was necessary. Atenolol blood levels at 36 and 60 hours after ingestion were 9.8 and 0.38 micrograms/ml respectively. The patient was discharged to a psychiatric department three days after admission. Conclusions: A poor correlation between beta-blockers blood levels and their toxic effect has already been observed, perhaps related to interindividual variability in pharmacokinetics and pharmacodynamics (3). However to our knowledge no cases of asymptomatic patients with such high atenolol levels have been reported before. Anamnesis, clinical presentation, BP and ECG monitoring are the most important parameters to consider in taking the proper decisions about treatment. Nonetheless in patients with toxic atenolol blood concentrations a non-invasive monitoring could be appropriate until normalization of atenolol levels even if asymptomatic.