There are a relatively small number of toxins that commonly lead to hypotension and bradycardia. It is important to make a correct diagnosis, as these drugs are among the most lethal and have specific antidotes.

• Calcium channel blocking drugs (CCBs)
• Beta adrenoceptor blocking drugs
• Digoxin

In addition there are a number of toxins that will occasionally lead to bradycardia and hypotension in very severe poisoning but which usually cause either tachycardia or no change to heart rate.

• Lithium
• Tricyclic antidepressants (TCAs)
• Neuroleptics
• Anticonvulsants
• Barbiturates
• Chloroquine
• Quinine
• Opioids
• Alcohol
• Organophosphates

Features that help to differentiate between these drugs are:

• RESPONSE TO PAINFUL STIMULI
• PUPIL SIZE & REACTION
• MYOCLONIC JERKING or HYPERREFLEXIA
• BOWEL SOUNDS
• ECG CHANGES
• RESPONSE TO ANTAGONISTS
• ELECTROLYTES/BLOOD GLUCOSE
• BLOOD CONCENTRATIONS