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  1. Nitroglycerin

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Show full transcript for Nitroglycerin video

In this lesson, we'll go over the medication nitroglycerin and all of its effects, including its mechanism of action, indications, precautions, contraindications, and adult dosages.

Nitroglycerin, a nitrate, causes smooth muscle relaxation. This produces systemic venous pooling of blood through the action of vasodilation. This, in effect, decreases venous blood flow return to the heart and reduces preload as well as venous afterload.

Pro Tip #1: The administration of nitroglycerin should be watched closely so as to not cause detrimental hypotension. Always monitor serial blood pressure and treat hypotension accordingly.

Nitroglycerin Indications

Nitroglycerin is clinically indicated to treat the following conditions:

  • To relieve chest discomfort suspected to be the result of an acute myocardial infarction (AMI).
  • To relieve cardiogenic pulmonary edema related to left-sided heart failure.
  • To provide coronary artery vasodilation in patients experiencing ischemic chest pain.

Nitroglycerin Precautions and Contraindications

There are multiple situations where the use of nitro may not be indicated, or may even be contraindicated and actually harmful to the outcome of the patient. Do not administer nitroglycerin if any of the following are present:

  • A low systolic blood pressure of less than 90 mmHg.
  • A suspected right-sided ventricular infarction.
  • Severe bradycardia of less than 50 beats per minute.
  • Tachycardia greater than 100 beats per minute in the absence of heart failure.
  • The patient has used tadalafil (Cialis or Adcirca) within the past 48 hours.
  • The patient has used a phosphodiesterase type 5 inhibitor, such as sildenafil (Viagra), within the past 24 hours. Mixing these medications can cause severe, life-threatening hypotensive side effects.

Pro Tip #2: Because of these severe drug interactions, it is vitally important to gather a thorough medication list from the patient, or from a reliable family member or caregiver, before administering nitroglycerin.

Adult Dosage of Nitroglycerin

When administering nitroglycerin to adult patients, look to the following protocol based on the route of administration:

  • Sublingual Tablets: Administer 0.4 mg (usually 1 tablet) sublingually. This can be repeated in 5-minute intervals to a maximum of three tablets.
  • Sublingual Spray: Administer 1 metered spray, which is equivalent to 0.4 mg. This can also be repeated in 5-minute intervals to a maximum of three sprays.
  • Intravenous (IV) Infusion: Begin the IV administration and increase by 10 mcg per minute every 3 to 5 minutes until you reach your desired clinical effect.