Nitroglycerin (NTG)

• Organic Nitrate–Vasodilator

• Dilation of both arteries and veins; veins initially dilated reducing preload; higher doses dilate arterioles reducing myocardial workload and oxygen demand
• Dilation of coronary arteries

Chest pain

• Stable angina–reduces oxygen demand of myocardium by reducing preload

• Variant angina–enhances oxygen supply to myocardium by relaxing and dilating coronary arteries

• Onset: 2 min (SL); 3 min (PO); 30 min (topical)
• Half-Life: 5-7 minutes
• Metabolism:  Metabolized in liver

• Headache
• Orthostatic hypotension
• Reflex tachycardia
• Flushing
• Lightheadedness, dizziness, syncope

• Hypotension
• Hypersensitivity (anaphylactic reaction = hives, dyspnea, itching, shock)

• Hypotension (Systolic BP < 90 mm Hg or more than 30 mm Hg below baseline)
• Recent use of phosphodiesterase inhibitors (sildenafil [Viagra^®] or vardenafil [Levitra^®]) within past 24 hours
• Recent use of phosphodiesterase inhibitor (tadalafil [Cialis^®]) within past 48 hours
• Right ventricular infarction (inferior wall MI)

• PO: (sustained release tablet or capsule)
• SL:  0.3 – 0.4 mg tablet q 5 minutes for a total of 3 doses
• Intravenous Drip:  Begin at 5 mcg/min and titrate every 3-5 minutes to therapeutic response and stable vital signs.  Titrate NTG infusion until relief of chest pain or maximum of 200 mcg/min dose is achieved.
• Topical:  Transdermal patch q 24 hours for 10-12 hour duration (with at least 12 hours NTG free out of each 24 hour period)

• Check blood pressure and pulse before each administration of NTG–blood pressure can drop precipitously after a single dose.  Hold dose if systolic BP < 90 mm Hg or more than 30 mm Hg below baseline.
• NTG is highly unstable and should be stored in light resistant container in cool environment (not the refrigerator).
• If SL tablets are not bitter, they have probably lost their potency.
• Tolerance occurs during continuous administration of NTG; blood vessels do not respond as well to NTG.  Therefore, patches or topical ointments are removed for 12 hours every day to reduce tolerance.
• Acute chest pain is treated with either SL tablets or spray or with IV infusion of NTG.
• Maintenance therapy to prevent angina is managed with topical applications or sustain-released oral medication.
• Intravenous infusion of NTG requires special glass bottles and IV tubing (regular plastic tubing will absorb 40-80% of NTG).
• Do not discontinue NTG intravenous infusion abruptly–it may result in precipitous rebound hypertension, angina, or coronary artery vasospasms.
• Acetaminophen is generally given PO for relief of headache secondary to NTG therapy.