For symptomatic bradycardia, what is the initial IV atropine dose?

• A. 0.5 mg IV, may repeat every 3–5 minutes to a maximum of 3 mg
• B. 1 mg IV
• C. 2 mg IV
• D. 0.1 mg IV

Answer: (A)

In symptomatic bradycardia, the aim is to counteract excessive vagal (parasympathetic) input to the heart so the SA node fires more quickly and AV conduction improves. Atropine achieves this by blocking muscarinic receptors, which reduces vagal tone and increases heart rate.

The recommended initial IV dose is 0.5 mg given as a bolus. If the patient doesn’t respond adequately, repeat every 3–5 minutes, up to a total maximum of 3 mg. This approach starts with a small, safe amount and titrates to effect, while minimizing anticholinergic side effects that can accompany higher initial doses.

Smaller doses like 0.1 mg are typically too weak to reliably counteract vagal excess, while higher single doses (1 mg or 2 mg) are not necessary as the starting approach and carry more risk if not needed. If atropine fails to improve the bradycardia or if the rhythm is a high-grade AV block, other measures such as pacing or vasoactive infusions are considered.