In comparison to less fat-loving drugs (like the water-soluble atenonol), propanolol is better able to penetrate cardiac and CNS tissues. The reason behind this increased toxicity was thought to be related to the high lipophilicity of propanolol. However, the seizure thing is well documented: for instance, in the case series by Reith et al (1996) two thirds of the patient who took over 2g of propanolol ended up having seizures. This may seem weird, as a sodium channel blocker is supposed to act as a membrane stabiliser. In the brain, propanolol decreases the seizure threshold. It has nasty sodium channel blocking effects and it prolongs QRS duration moreover it penetrates the blood brain barrier. Most deaths from β-blocker overdose are associated with propanolol.
However, a few stand out as being particularly toxic. This table is very similar to the one offered in Goldfranks' Manual of Toxicologic Emergencies.Įven though one cannot call any β-blocker overdose intrinsically "safe", many drugs are relatively benign. Pharmacological properties of commonly used β-blockers Additional resources should include the LITFL CCC entry, which is clear and concise. The cardinal differences in β-blocker and CCB toxicological syndromes are discussed at the very end of this chapter, which otherwise mainly deals with β-blockers on their own.
Question 14 from the second paper of 2006 asked the candidates to compare beta blockers and calcium channel blockers in a "compare and contrast" table.Īn ideal resource for answering such a question can be found in DeWitt and Waksman's article from Toxicological reviews (2004) - they basically answer the college questions for you.Question 2 from the first paper of 2017 had presented the candidates with an ECG of a patient suffering from complete heart block after being dosed with both sotalol and verapamil, something best discussed in the chapter on toxic antiarrhythmic polypharmacy.Question 7 from the second paper of 2017 also asked for the antidote.Question 3 from the first paper of 2022 had asked for the antidote, and mechanism of its action.Beta blocker overdose has appeared several times in the CICM Part II exam.
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