Common use of Nitroglycerin
Nitroglycerin is indicated for the acute relief of angina pectoris and for prophylaxis of predictable exertional angina. By donating nitric oxide and increasing cyclic GMP, it relaxes vascular smooth muscle, primarily venous capacitance vessels, decreasing preload and myocardial oxygen demand. It also dilates coronary arteries and can improve subendocardial perfusion.
In emergency settings, intravenous nitroglycerin is used under continuous monitoring in acute coronary syndromes and decompensated heart failure with pulmonary edema to reduce ischemia and congestion. Topical nitroglycerin preparations are occasionally used for persistent angina symptoms; a distinct 0.4% intra-anal ointment formulation is prescribed for chronic anal fissure to reduce sphincter spasm and pain.
Sublingual tablets and sprays provide rapid onset for breakthrough chest pain or pre-exertional prevention. Transdermal patches deliver sustained prophylaxis when applied daily with a nitrate-free interval to minimize tolerance.
Dosage and direction
Acute angina relief (sublingual tablets): Place 0.3 mg to 0.6 mg under the tongue at the first sign of chest pain. Do not chew or swallow; allow it to dissolve. If pain persists, you may repeat the dose every 5 minutes, up to 3 doses in 15 minutes. If symptoms do not improve after 1 dose, especially if you suspect a heart attack, call emergency services immediately.
Acute angina relief (metered spray): Administer 0.4 mg per spray onto or under the tongue; do not inhale. Repeat every 5 minutes as needed for up to 3 sprays. Avoid eating, drinking, or rinsing for several minutes after use.
Prevention of exertional angina: Take one sublingual tablet (0.3–0.6 mg) or one 0.4 mg spray 5 to 10 minutes before activity known to precipitate chest pain. This pre-exertional dosing can reduce or prevent symptoms during predictable triggers.
Chronic prophylaxis (transdermal patches/ointment): Typical patch delivery rates are 0.2 to 0.4 mg/hour applied to clean, hairless skin. To avoid tolerance, use a daily nitrate-free interval of 10 to 12 hours (e.g., remove patch at night). Ointment doses are measured in inches on dosing paper and applied to the chest or back; follow the specific product’s dosing instructions and maintain a nitrate-free period daily.
Intravenous infusion: Initiated at low rates (e.g., 5–10 mcg/min) and titrated to effect under continuous blood pressure and symptom monitoring in hospital settings only. IV nitroglycerin is not for self-administration.
Anal fissure (0.4% nitroglycerin ointment): Apply a small amount intra-anally as directed, generally every 12 hours for up to 3 weeks. Headache is common; counsel on proper application to minimize systemic absorption.
General directions: Sit or lie down before dosing to reduce dizziness or fainting. Do not abruptly stop chronic nitrate therapy without medical guidance. Your clinician may adjust dose and formulation based on symptom pattern, blood pressure, and tolerance.
Precautions
Nitroglycerin can cause sudden drops in blood pressure, lightheadedness, and fainting. Always sit or lie down during acute dosing and rise slowly afterward. Avoid driving or operating machinery until you know how you respond. Alcohol and hot environments can amplify hypotension.
Tolerance can develop with continuous exposure; adhere to nitrate-free intervals for patches/ointments. People with low baseline blood pressure, volume depletion, or autonomic dysfunction are at higher risk for symptomatic hypotension. Use with caution in hypertrophic cardiomyopathy with outflow obstruction or suspected right ventricular infarction, where preload reduction may worsen hemodynamics.
Pregnancy and lactation: Use only if the potential benefit justifies the potential risk; consult your clinician. For pediatric use, safety and efficacy are not established.
Contraindications
Do not use nitroglycerin if you have taken a phosphodiesterase-5 inhibitor such as sildenafil or vardenafil within the past 24 hours, or tadalafil within the past 48 hours, due to the risk of profound, life-threatening hypotension. Concomitant use with riociguat (a soluble guanylate cyclase stimulator) is also contraindicated.
Other contraindications include severe hypotension or shock, marked anemia, increased intracranial pressure or recent intracranial hemorrhage, and known hypersensitivity to organic nitrates. Patients with acute inferior myocardial infarction with suspected right ventricular involvement require extreme caution and specialized management.
Possible side effects
Common side effects include throbbing headache, flushing, dizziness, lightheadedness, and a sense of warmth. These often lessen with continued use or dose adjustment. Taking the first dose while seated and avoiding abrupt posture changes can reduce symptoms.
Less common effects are nausea, vomiting, palpitations, reflex tachycardia, and weakness. Topical or transdermal preparations may cause local skin irritation or dermatitis; rotating application sites and using clean, dry skin helps prevent irritation.
Rare but serious adverse effects include severe hypotension, syncope, and methemoglobinemia (manifested by cyanosis unresponsive to oxygen, unusual fatigue, or shortness of breath). Seek urgent care for persistent chest pain despite dosing, severe dizziness, fainting, visual disturbances, or shortness of breath.
Drug interactions
Absolute interaction: Phosphodiesterase-5 inhibitors (sildenafil, vardenafil, tadalafil) and riociguat. Combining these with nitroglycerin can cause precipitous, dangerous drops in blood pressure. Strictly separate timings as noted in contraindications and discuss with your clinician before resuming nitrates after PDE-5 use.
Significant additive effects: Other antihypertensives (beta-blockers, calcium channel blockers, alpha-blockers), tricyclic antidepressants, antipsychotics, and alcohol can enhance hypotension or dizziness. Use caution, monitor blood pressure, and adjust therapy as advised.
Additional considerations: Ergot derivatives (e.g., dihydroergotamine) may antagonize antianginal effects or raise blood pressure. In hospital settings, high-dose IV nitroglycerin can reduce the anticoagulant effect of heparin, warranting closer monitoring. Always provide your full medication and supplement list to your pharmacist or clinician.
Missed dose
PRN sublingual tablets or sprays are taken only when needed for acute chest pain or before exertion; the concept of a “missed dose” does not apply. Keep the medication accessible at all times for prompt use.
For scheduled transdermal or ointment regimens, if you miss a dose and it is close to the next scheduled application, skip the missed dose and resume the regular schedule. Do not double up or wear patches longer than prescribed to “catch up,” and maintain the nitrate-free interval to prevent tolerance.
Overdose
Symptoms may include severe headache, flushing, profound hypotension, tachycardia, blurred vision, confusion, nausea, vomiting, fainting, shortness of breath, and in rare cases methemoglobinemia with bluish discoloration of lips or skin. Overdose can occur with excessive patch exposure, multiple acute doses in short succession, or accidental ingestion.
Immediate actions: Call emergency services or poison control. Lie down with legs elevated while awaiting help. Do not induce vomiting. In medical settings, management is supportive with IV fluids, positioning, and, if methemoglobinemia is confirmed, treatment with methylene blue.
Storage
Store sublingual tablets in the original, tightly closed glass container to protect from light and moisture; do not transfer to pill organizers. Keep at room temperature and away from heat or humidity (not in a bathroom or car). Metered spray should remain upright, away from flames or high heat, and capped when not in use.
Transdermal patches and ointments should be kept at controlled room temperature in their original packaging. Always check expiration dates, keep out of reach of children and pets, and dispose of used patches by folding them adhesive sides together.
U.S. Sale and Prescription Policy
In the United States, nitroglycerin is a prescription medication. While online ads may suggest you can “buy nitroglycerin without prescription,” U.S. law requires a valid prescription for legal dispensing. This protects patients by ensuring proper diagnosis of chest pain, screening for dangerous interactions (notably with PDE-5 inhibitors), and education on emergency use.
HealthSouth Hospital of Altamonte Springs offers a legal, structured pathway to access nitroglycerin that keeps you within regulatory and clinical safety standards. Options include coordinating with licensed clinicians for timely telehealth evaluation, transferring an existing valid prescription from another pharmacy, or collaborating with your cardiology practice to streamline refills—all while providing pharmacist counseling on correct use and nitrate-free intervals.
This compliant approach gives you the convenience people often seek from “no-prescription” websites, without the risk. If you experience new or worsening chest pain, seek emergency care rather than relying on online sources. For ongoing management and appropriate prescriptions, contact HealthSouth Hospital of Altamonte Springs to discuss safe, supervised access to nitroglycerin and related cardiac therapies.
