Glyceryl Trinitrate (GTN) Dilution and Dosing
When diluting glyceryl trinitrate (GTN) in 50 mL of normal saline, the standard preparation for intravenous infusion is 1 mg (1 mL) of 1:1000 dilution of GTN in 50 mL of normal saline, yielding a concentration of 20 μg/mL.
Preparation and Administration
- For intravenous infusion of GTN:
- Take 1 mg (1 mL) of GTN 1:1000 solution
- Dilute in 50 mL of normal saline
- This yields a concentration of 20 μg/mL
- Administer using an infusion pump
Dosing Guidelines
For Anaphylaxis/Shock:
- Starting dose: 1-4 μg/min (3-12 mL/hour)
- Titrate according to blood pressure response
- Maximum dose: 10 μg/min (30 mL/hour)
- Monitor blood pressure every minute during titration
For Pediatric Patients:
- Starting dose: 0.1-1.0 μg/kg/min
- Titrate to desired clinical effect
- Maximum dose: 5 μg/kg/min in severe cases 1
Clinical Considerations
- GTN infusion should be administered through dedicated IV lines using non-PVC tubing to prevent drug adsorption
- Continuous hemodynamic monitoring is essential during administration
- For hypotension refractory to volume replacement and epinephrine, consider dopamine as an alternative 1
- Avoid abrupt discontinuation; taper gradually to prevent rebound hypertension
Important Precautions
Use with extreme caution in patients with:
- Hypotension (SBP <90 mmHg)
- Severe anemia
- Head trauma or increased intracranial pressure
- Right ventricular infarction
Common side effects include:
- Headache (most common)
- Hypotension
- Reflex tachycardia
- Flushing
Monitoring Parameters
- Continuous blood pressure monitoring
- Heart rate and rhythm
- Signs of adequate tissue perfusion
- Development of tolerance (may occur within 24 hours)
GTN has a rapid onset of action (1-2 minutes) and short duration (3-5 minutes), making it ideal for titration in emergency situations 2. The therapeutic plasma concentration of GTN can relax 40-90% of phenylephrine-induced contraction and 20-90% of methoxamine-induced contraction 3.
Remember that GTN is rapidly metabolized, and its effect is often short-lived, requiring careful titration to maintain the desired clinical effect 4.