Isosorbide dinitrate

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Isosorbide dinitrate is a medicinal nitrate used for dilating blood vessels. It is prescribed for preventing chest pain and for those diagnosed with coronary artery disease. Some physicians are currently prescribing this drug to relieve pain, swallowing difficulties, and esophageal spasms in gastro-esophageal reflux.

It does not prevent chest pain when it happens and is not intended to prevent chest pain just before engaging in strenuous activities such exercise or sexual intercourse. It is also known as nitroglycerin, ISD, or ISDN. People may develop tolerance with this drug when used long term. To prevent physiologic tolerance of the drug, a daily 10-hour drug free period is observed.

Contents

Chemical nature

Chemically, isosorbide dinitrate is known as 1,4:3,6-dianhydro-2,5-di-O-nitro-D-glucitol or (3R,3aS,6S,6aS)-hexahydrofuro[3,2-b]furan-3,6-diyl dinitrate. It has a chemical formula of C6H8N2O8 and comes from an organic sugar known as sorbitol. Its effect is visible within 6 minutes with extended release effects that will last for 12 hours. Toxic dose is known to be 1.1 grams

The vasodilating action of isosorbide dinitrate is through the relaxing action in blood vessels of nitrates, particularly nitric oxide. This will decrease the oxygen demand of the heart and preventing chest pain. This mechanism of action is very similar to glyceryl trinitrate (also known as nitroglycerin).

Uses and common dosages

Isosorbide dinitrate must be taken at the same time each day. It should be swallowed whole for oral tablets or placed under the tongue for sublingual tablets.

Oral and sublingual

  • Long term treatment of chest pain - Patients may be given 20 to 120 milligrams orally per day in equally divided doses.
  • Acute chest pain - Sublingual tablets of 5 to 15 milligrams can be placed under the tongue every 2 to 3 hours. With a 1.25 milligram dose per spray, 1 to 3 sprays under the tongue is sufficient to relieve chest pain.
  • Heart failure - With oral tablets, 30 to 160 milligrams per day may be given in divided doses. This must not exceed 240 milligrams within 24 hours. With sublingual tablets, 5 to 15 milligrams may be given every 2 to 3 hours.
  • Esophageal spastic disorders - Oral tablets of 5 to 10 milligrams may be given before meals. Sublingual tablets of 2.5 milligrams are taken after meals.

Intravenous and intracoronary

  • Heart failure - A dose of 2 to 12 milligrams per hour may be titrated. This must not exceed 20 milligrams per hour.
  • Unstable angina - Titrations of 2 to 12 milligrams per hour are usually given. This should not be more than 20 milligrams per hour.
  • Percutaneous transluminal coronary angioplasty - Bolus dose of 1 milligram may be given intracoronary before balloon inflation. A maximum dose of 5 milligrams may be given within the 30-minute period.

Side effects

As the body adjusts to isosorbide dinitrate, the following symptoms may be experienced:

  • Throbbing headache
  • Transient episodes of dizziness and weakness
  • Lightheadedness
  • Nausea
  • Flushing

However, if these symptoms occur, the doctor must be informed immediately for dosage adjustment or change of medication:

  • Fainting, dizziness, or confusion
  • Vomiting or abdominal pain
  • Fast, iregular heartbeat
  • Allergic reactions
  • Very low blood pressure and slow heart beats
  • Medicine rash (exfoliative dermatitis)

Precautions and contraindications

There are some conditions that the doctor or the pharmacist may need to know before prescribing or dispensing isosorbide dinitrate. These include:

  • Allergies to nitrate containing drugs
  • Recent head injury
  • Gastrointestinal hypermotility (i.e. frequent stomach cramps, watery stools, or severe diarrhea)
  • Malabsorption (inability to absorb nutrients properly)
  • Hypothyroidism
  • Severely impaired renal or hepatic function
  • Has increased eye pressure
  • Intracranial pressure because of head trauma or cerebral hemorrhage
  • Scheduled surgery or major dental procedure.
  • Circulatory problems (i.e.[[[anemia]] or low blood pressure)
  • Dehydration
  • Other heart problems (i.e. recent heart attack or congestive heart failure)
  • Pregnant or trying to get pregnant and breastfeeding

Some medications may interact adversely with isosorbide dinitrate. The prescriber must be informed if these drugs will be used concurrently:

  • Drugs used to treat erectile dysfunction (i.e. sildenafil, tadalafil, and vardenafil)
  • Rosiglitazone
  • Drugs for migraine headaches (i.e. ergotamine)
  • Drugs that lower blood pressure (i.e. alpha blockers like tamsulosin or calcium channel blockers)
  • Alcohol

Availability

In the Philippines, oral and sublingual tablets of isosorbide dinitrate are readily available in drug stores. Popular brands include Isordil ® and Isoket ® that provide both immediate release oral and sublingual tablets. However, the latter has more versatile formulations as it also provides the retard tablets, the sublingual spray, and the ampoule.

References