Are glyceryl nitrate (nitroglycerin) and sorbitrate (isosorbide dinitrate) the same?

Glyceryl Nitrate (Nitroglycerin) and Isosorbide Dinitrate (Sorbitrate) Are Different Medications

No, glyceryl nitrate (nitroglycerin) and isosorbide dinitrate (sorbitrate) are not the same medication, though they both belong to the organic nitrate class of vasodilators with similar therapeutic effects. 1, 2, 3

Key Differences Between the Medications

• Chemical Structure:

  • Nitroglycerin (glyceryl trinitrate) has the chemical name 1,2,3-propanetriol trinitrate 2
  • Isosorbide dinitrate has the chemical name 1,4:3,6-dianhydro-D-glucitol 2,5-dinitrate 3

• Duration of Action:

  • Nitroglycerin (sublingual): 1-7 minutes 1
  • Isosorbide dinitrate (oral): Up to 8 hours 1
  • Studies show isosorbide dinitrate's hemodynamic effects last 8-12 times longer than nitroglycerin 4

• Available Formulations:

  • Nitroglycerin: Sublingual tablets, spray, transdermal patches, intravenous 1
  • Isosorbide dinitrate: Oral tablets (regular and slow-release), sublingual 1

Similarities in Mechanism and Clinical Use

• Mechanism of Action: Both medications are organic nitrates that act as vasodilators through:

  • Dilation of venous capacitance vessels (decreasing preload) 1
  • Modest effects on arterial circulation (decreasing afterload) 1
  • Promotion of coronary artery dilation and improved collateral flow 1
  • Mediation of vascular smooth muscle relaxation through nitric oxide and cyclic guanosine monophosphate pathways 1

• Clinical Applications: Both are used for:

  • Treatment of angina pectoris 1
  • Management of heart failure 1
  • Vasospastic conditions 1

Practical Considerations in Clinical Use

• Dosing Differences:

  • Nitroglycerin:
    • Sublingual: 0.3-0.6 mg up to 1.5 mg
    • IV: 5-200 mcg/min 1
  • Isosorbide dinitrate:
    • Oral: 5-80 mg, 2-3 times daily
    • Slow-release: 40 mg 1-2 times daily 1

• Tolerance Development:

  • Both medications develop tolerance after continuous use (typically within 24 hours) 1, 5
  • A nitrate-free interval of at least 10 hours is recommended to minimize tolerance 1
  • Cross-tolerance exists between these medications 6

• Contraindications for Both:

  • Use with phosphodiesterase inhibitors (e.g., sildenafil, tadalafil, vardenafil) due to risk of profound hypotension 1
  • Hypotension (systolic BP <90 mmHg) 1

Clinical Decision Making

When choosing between these medications, consider:

1. Onset and duration needed:

   • For acute angina: Nitroglycerin provides faster onset 1
   • For prophylaxis: Isosorbide dinitrate offers longer duration 4

2. Route of administration:

   • Sublingual/spray for immediate relief (nitroglycerin) 1
   • Oral for maintenance therapy (isosorbide dinitrate) 1

3. Hemodynamic stability:

   • Some studies suggest isosorbide dinitrate may have less effect on blood pressure and heart rate compared to nitroglycerin in certain patient populations 7

Remember that while these medications are different chemical entities, they share the same class effects, contraindications, and potential adverse effects including headache, hypotension, and reflex tachycardia 1.