Glyceryl trinitrate

Indications

• • angina

• heart failure

Administration/Absorption

• • The effectiveness of glyceryl trinitrate is limited by development of tolerance/tachyphylaxis within 2-3 weeks of sustained use

  • Continuous administration and absorption accelerate onset of tolerance and limit the usefulness of the agent

  • Thus glyceryl trinitrate works best when used only short term, pulse dosing

    • tablet placed under the tongue or a spray into the mouth

Dosage

Distribution

Mechanism

• • Vasodilator

  • prodrug which must first be denitrated to produce the active metabolite NO

  • NO is a potent activator of guanylyl cyclase (GC) by heme-dependent mechanisms

    • results in cGMP formation from guanosine triphosphate (GTP)

    • cGMP then activates myosin light chain phosphatase via a cGMP-dependent protein kinase.

Excretion

Side effects

• • severe headaches

  • severe hypotension

• bradycardia

  • syncope

  • heartburn

  • flushing

  • site reactions in mouth

Interactions

• • vasodilators that combat erectile disfunction, such as Viagra, Cialis, or Levitra

Contraindications

• • Anaemia

  • Cerebrovascular disease

  • Toxic pulmonary oedema