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Nitroglycerin; Uses, Dosage, Side Effects, Interactions, Pregnancy

Nitroglycerin is an organic nitrate with vasodilator activity. Nitroglycerin is converted into nitric oxide (NO) in smooth muscle and activates guanylyl cyclase, thereby increasing cGMP concentration, and resulting in smooth muscle relaxation. Dilatation of the veins results in the decreased venous return to the heart, thereby decreasing left ventricular volume (reduced preload) and decreasing myocardial oxygen requirements. Arteriolar relaxation reduces arteriolar resistance (reduced afterload), thereby decreasing myocardial oxygen demands. In addition, nitroglycerine causes coronary artery dilatation, thereby improving myocardial blood distribution.

Nitroglycerin, an organic nitrate, is available in many forms as a vasodilator. Nitroglycerin is used in the treatment of angina pectoris and perioperative hypertension, to produce controlled hypotension during surgical procedures, to treat hypertensive emergencies, and to treat congestive heart failure associated with myocardial infarction. Nitroglycerin is also a major component in double-based smokeless gunpowders used by reloaders. Combined with nitrocellulose, there are hundreds of powder combinations used by rifle, pistol, and shotgun reloaders.

Mechanism of action of Nitroglycerin

Similar to other nitrites and organic nitrates, nitroglycerin is converted to nitric oxide (NO), an active intermediate compound which activates the enzyme guanylate cyclase. This stimulates the synthesis of cyclic guanosine 3′,5′-monophosphate (cGMP) which then activates a series of protein kinase-dependent phosphorylations in the smooth muscle cells, eventually resulting in the dephosphorylation of the myosin light chain of the smooth muscle fiber. The subsequent release of calcium ions results in the relaxation of the smooth muscle cells and vasodilation.

The drugs used to treat angina alleviate symptoms by increasing blood flow to the ischemic myocardium and/or by reducing myocardial oxygen requirements. Nitrates reduce myocardial oxygen requirements through their effects on the systemic circulation. Their major systemic action is a reduction in venous tone, which leads to pooling of blood in peripheral veins, decreased venous return, and reduced ventricular volume and myocardial tension (preload).

Although it predominately affects vascular smooth muscle nitroglycerin, the bronchioles, gastrointestinal tract (including biliary system), ureters, and uterus are affected. Free radicals of nitric oxide may activate guanylate cyclase, resulting in increased synthesis of cyclic GMP. Nitric oxide may combine with sulfhydryl groups in the endothelium and produce S-nitrosothiols, which stimulate guanylate cyclase production. N-acetyl-cycteine may enhance this process by providing a source of sulfhydryl groups. Cyclic GMP appears to reduce stored calcium and interfere with calcium-activated smooth muscle contractions.

Indications of Nitroglycerin

Acutely decompensated heart failure
Angina pectoris
Angina attack
High Blood Pressure
Left ventricular dysfunction
Atrial fibrillation
Heart failure
Chronic stable angina pectoris
Chronic anal fissures
Gastroesophageal variceal hemorrhage prophylaxis
Procedural hypertension
Esophageal spastic disorders
Chest pain associated with restricted blood supply
Heart’s left ventricular failure accompanying the heart attack
Sudden and intense vasoconstriction heart arteries
High blood pressure during cardiac surgery

Therapeutic Indications

Nitroglycerin can provide dramatic relief of paroxysmal nocturnal dyspnea, probably as result of improved left ventricular function and reduced pulmonary arterial pressure. Topical application of ointment may provide cutaneous vasodilation, particularly in the treatment of Raynaud’s disease and healing of trophic ulcers.
Sublingually too short-acting, orally minimally effective but topically, effects prolonged making it potentially useful in chronic vasodilator therapy.
Sublingual nitroglycerin was beneficial in the emergency treatment of classic pulmonary edema. Elevated ventricular filling pressure decr and cardiac output incr.
Patients received 0.3 mg of glyceryl nitrate 1-4 times/day sublingually for treatment of chest pain. Two days later patients experienced the 1st erection in 2.5 yr lasting 10 min and reoccurred 3-4 times/wk. Suggests the vasodilatory effect.
In a comparative study, it was concluded that nitroglycerin given daily had longer action than isosorbide dinitrate and that in persisting angina, propranolol should be added or substituted to previous therapy.
It produced the slight positive inotropic effect and increased ventricular performance associated with a reduction in myocardial oxygen consumption and in coronary blood flow.
When admin topically, nitroglycerin appeared to be as effective as when admin sublingually for treatment of myocardial ischemia, and its prolonged action makes it useful as the prophylactic agent.
A review on long-acting nitrates and nitroglycerin, especially for treatment of angina and congestive heart failure. Oral, sublingual, transdermal, and buccal formulations are discussed.
After 100 years of use for relieving angina pectoris, nitroglycerin is finding wider application in congestive heart failure, limiting myocardial “infarct size,” and long time angina prophylaxis, and as a diagnostic test for the presents of myocardial ischemia.
Nitroglycerin shares the actions of the other nitrates and nitrites and is used for the acute relief of angina pectoris secondary to coronary artery disease, for prophylactic management in situations likely to provoke angina attacks, and for long term prophylactic management of angina pectoris.
IV nitroglycerin is used to control blood pressure in perioperative hypertension, especially hypertension associated with cardiovascular procedures; to control blood pressure in patients with severe hypertension or in hypertensive crises for the immediate reduction of blood pressure in patients in whom such reduction is considered an emergency, especially those associated with coronary complications; for the treatment of ischemic pain, congestive heart failure, or pulmonary edema associated with acute myocardial infarction.
The use of nitroglycerin is one of the principal initial therapies in the management of patients with acute myocardial infarction. The drug has been used to reduce myocardial ischemia, alleviate ischemia induced-pain, manage hypertension and persistent pulmonary congestion, and decrease the extent of infarction during and improve survival after acute myocardial infarction.
The nitrovasodilators act on almost all smooth muscle. Bronchial smooth muscle is relaxed irrespective of the cause of the preexisting tone. The muscles of the biliary tract, including those of the gallbladder, biliary ducts, and sphincter of Oddi, are effectively relaxed. Smooth muscle of the gastrointestinal tract, including that of the esophagus, can be relaxed and its spontaneous motility decreased by nitrates both in vivo and in vitro.

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Contra Indications of Nitroglycerin

Liver problems
Blockage of a bile duct
Kidney disease with the reduction in kidney function
Pregnancy
Second and third trimester of pregnancy
Biliary obstructive disorders.
Severe hepatic impairment.
Hypersensitivity to the active substance or to any of the excipients
Severe anemia
Methemoglobinemia
Severe heart failure
hemorrhage in the brain
abnormally low blood pressure
High pressure within the skull

Dosage of Nitroglycerin

Strengths: 0.3 mg, 0.4 mg, 0.6 mg;

Myocardial Infarction

Intra venous solution

5 mcg/min continuous IV infusion via non-absorptive tubing; increase by 5 mcg/min every 3 to 5 minutes as needed up to 20 mcg/min, then by 10 or 20 mcg/min if needed

Angina Pectoris

5 mcg/min continuous IV infusion via non-absorptive tubing; increase by 5 mcg/min every 3 to 5 minutes as needed up to 20 mcg/min, then by 10 or 20 mcg/min if needed

Spray

1 to 2 sprays (0.4 to 0.8 mg) on or under tongue every 5 minutes as needed, up to 3 sprays in 15 minutes; if pain persists after maximum dose, prompt medical attention is recommended

Sublingual tablet

0.3 to 0.6 mg sublingually or in the buccal pouch every 5 minutes as needed, up to 3 doses in 15 minutes; if pain persists after maximum dose, prompt medical attention is recommended

Angina Pectoris Prophylaxis

Lingual spray

1 to 2 sprays (0.4 to 0.8 mg) on or under tongue 5 to 10 minutes prior to activity that might precipitate an acute attack

Sublingual tab

0.3 to 0.6 mg sublingually or in the buccal pouch 5 to 10 minutes prior to engaging in activities that might precipitate an acute attack

Topical ointment

1/2 inch (7.5 mg) topically upon rising and 1/2 inch (7.5 mg) 6 hours later; titrate as needed and tolerated

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Transdermal patch

0.2 to 0.4 mg/hr patch applied topically once a day for 12 to 14 hours per day; titrate as needed and tolerated up to 0.8 mg/hr

Extend release capsule

2.5 to 6 mg orally 3 to 4 times a day; titrate as needed and tolerated

Hypertension

Intra venous solution

5 mcg/min continuous IV infusion via non-absorptive tubing; increase by 5 mcg/min every 3 to 5 minutes as needed up to 20 mcg/min, then by 10 or 20 mcg/min if needed

Side Effects of Nitroglycerin

The most common

Common

chills or fever
a headache, severe and throbbing
joint or back pain
muscle aching or cramping
muscle pains or stiffness
chest pressure or squeezing pain in the chest
excessive sweating
sudden drowsiness or need to sleep
sharp pain when taking a deep breath
coughing up blood
rust colored urine
liver problems–nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes)
decreased amount of urine

Rare

Anxiety
change in vision
chest pain or tightness
confusion
a cough
Agitation
arm, back, or jaw pain
blurred vision
chest pain or discomfort
convulsions
extra heartbeats
hallucinations
a headache
irritability
lightheadedness
cold and clammy skin
fast and shallow breathing

Drug Interactions of Nitroglycerin

Some drug may change how your medications work or increase your risk for serious side effects. You should not take nitroglycerin if you are taking the following drugs:

Stendra (avanafil)
Viagra (sildenafil)
Cialis (tadalafil)
Levitra (vardenafil)
Arginine, Acetadote (acetylcysteine) ,Selzentry (maraviroc)
Medications for Parkinon’s disease, like Caberlin (carbegoline), Azilect (rasagiline), and Emsam, Elderpryl or Zelapar (selegiline)
Ergot-containing medications for migrainesm like Cafergot (ergotamine), Migranal (dihydroergotamine), and Methergine (methylergonovine)

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This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist.

Pregnancy & Lactation of Nitroglycerin

FDA Pregnancy Category B

Pregnancy

Animal reproduction and teratogenicity studies have not been conducted with nitroglycerin sublingual tablets. However, teratology studies conducted in rats and rabbits with topically applied nitroglycerin ointment at dosages up to 80 mg/kg/day and 240 mg/kg/day, respectively revealed no toxic effects on dams or fetuses.

There are no adequate and well-controlled studies in pregnant women. Nitroglycerin should be given to a pregnant woman only if clearly needed.

Lactation

It is not known whether nitroglycerin is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when nitroglycerin is administered to a nursing woman. The safety and effectiveness of nitroglycerin in pediatric patients have not been established.