Does glucagon interact with Tikosyn (dofetilide) or Toprol (metoprolol)?

Glucagon Interactions with Tikosyn (Dofetilide) and Toprol (Metoprolol)

Glucagon does not have significant interactions with Tikosyn (dofetilide), but it may potentially reduce the effectiveness of Toprol (metoprolol) in certain clinical scenarios.

Glucagon and Tikosyn (Dofetilide)

Glucagon is primarily used for the emergency treatment of severe hypoglycemia in patients with diabetes who are unable to consume oral carbohydrates. Based on available evidence, there are no documented significant interactions between glucagon and dofetilide.

• Dofetilide is a Class III antiarrhythmic drug used for the treatment of atrial fibrillation 1
• Current guidelines do not list glucagon as having interactions with dofetilide
• The primary concern with dofetilide is its risk of causing QT prolongation and torsades de pointes, but glucagon is not known to exacerbate these effects

Glucagon and Toprol (Metoprolol)

Glucagon may counteract some of the therapeutic effects of metoprolol, particularly in specific clinical scenarios:

Mechanism of Interaction

• Glucagon increases heart rate and myocardial contractility through a mechanism that bypasses beta-adrenergic receptors 2
• This action can potentially counteract the beta-blocking effects of metoprolol

Clinical Implications:

1. Emergency Treatment of Beta-Blocker Overdose

   • Glucagon is actually recommended for treating beta-blocker overdose, including metoprolol overdose 3
   • The recommended dose for beta-blocker toxicity is a bolus of 3-10 mg administered slowly over 3-5 minutes, followed by an infusion of 3-5 mg/h 3

2. Hypoglycemia Management in Patients on Beta-Blockers

   • Metoprolol can impair glucose recovery from insulin-induced hypoglycemia in patients with diabetes 4
   • When glucagon is used to treat hypoglycemia in patients taking metoprolol, its glucose-raising effect remains intact, but its cardiovascular effects may partially counteract metoprolol's intended therapeutic effects

3. Stress Testing

   • Research has shown that glucagon does not fully reverse metoprolol's effects during dobutamine stress testing 5

Clinical Management Recommendations

1. For patients on Tikosyn (dofetilide):

   • Glucagon can be safely prescribed and administered when indicated for hypoglycemia
   • No special precautions or dose adjustments are necessary

2. For patients on Toprol (metoprolol):

   • Glucagon should still be prescribed for patients at risk of severe hypoglycemia 3
   • Be aware that after glucagon administration for hypoglycemia, temporary changes in heart rate and blood pressure may occur due to partial antagonism of metoprolol's effects
   • Monitor vital signs after glucagon administration in patients on metoprolol
   • Consider that patients with diabetes on metoprolol may have impaired recovery from hypoglycemia and might require closer monitoring 4

Important Considerations for Glucagon Use

• All patients treated with insulin or at high risk of hypoglycemia should be prescribed glucagon 3
• Newer glucagon formulations (intranasal and ready-to-inject) are preferred due to ease of administration 3
• Family members and caregivers should be instructed on proper glucagon administration 3
• Glucagon has a short duration of action, so patients should consume oral carbohydrates once conscious to prevent recurrent hypoglycemia 3

In summary, while glucagon can be safely used with Tikosyn, its use in patients taking Toprol requires awareness of potential temporary antagonism of the beta-blocker's effects, though this interaction should not prevent its use when clinically indicated for hypoglycemia.