Bradycardias caused by poisoning are due to the toxin's effects on cardiovascular receptors and cellular channels and transport mechanisms and are often refractory to standard ACLS drugs. The most common drug classes responsible for bradycardias are calcium channel and beta blockers and digoxin (cardiac glycosides). Sodium channel blockers, clonidine, and opiates also can cause bradycardias. Antidotes are as follows:

• Glucagon 5-10mg IV bolus followed by 1-5 mg/hr (Always pretreat with antiemetic) - Beta Blockers
• Calcium infusion 1-3 grams IV Bolus - Calcium Channel Blockers
• High Dose Insulin Euglycemic therapy of reg insulin 0.5-2 unit/kg Bolus (ie. 100 Units) with D50 IV bolus followed by reg insulin 0.5-1 units/kg/hr and dextrose 0.5 grams/kg/hr - Calcium channel and Beta Blockers
• **Intravenous Lipid Emulsion therapy bolus 1.5 mL/kg of ILE 20% followed by an infusion of 0.25 mL/kg/min-  Very small subset of toxins. See below.
• Atropine 2mg IV - Acetylcholinestrase inhibitors (Organophosphates)
• Sodium Bicarbonate 1-3 amps IV - Sodium Channel Blockers
• Digibind  for acute toxicity10 vials IV (20 Vials in cardiac arrest) and for chronic toxicity 2 vials and repeat as needed - Cardiac gylcosides
• Narcan 2 mg IV repeat boluses up to 10 mg- Opiates and Clonidine

** ILE is recommended only in life threatening poisonings where other accepted therapies have been use first or in cardiac arrest clinical scenarios. 

References

Toxic Bradycardias in the Critically Ill Poisoned Patient. Givens M. Emergency Medicine International. Vol 2012.

The safety of high-dose insulin euglycaemia therapy in toxin-induced cardiac toxicity.Page CB, Ryan NM, et al. Clin Toxicol. 2017 Oct 26:1-6