Isordil

The principal pharmacological action of isosorbide dinitrate is relaxation of vascular smooth muscle and consequent dilatation of peripheral arteries and veins, especially the latter. Dilatation of the veins promotes peripheral pooling of blood and decreases venous return to the heart, thereby reducing left ventricular end-diastolic pressure and pulmonary capillary wedge pressure (preload). Arteriolar relaxation reduces systemic vascular resistance, systolic arterial pressure, and mean arterial pressure (afterload). Dilatation of the coronary arteries also occurs. The relative importance of preload reduction, afterload reduction, and coronary dilatation remains undefined.

Hemodynamic Effects

The ill effects of isosorbide dinitrate overdose are generally the results of isosorbide dinitrate's capacity to induce vasodilatation, venous pooling, reduced cardiac output, and hypotension. These hemodynamic changes may have protean manifestations, including increased intracranial pressure, with any or all of persistent throbbing headache, confusion, and moderate fever; vertigo; palpitations; visual disturbances; nausea and vomiting (possibly with colic and even bloody diarrhea); syncope (especially in the upright posture); air hunger and dyspnea, later followed by reduced ventilatory effort; diaphoresis, with the skin either flushed or cold and clammy; heart block and bradycardia; paralysis; coma; seizures; and death.

Side Effects

Less serious side effects may be more likely to occur, such as:

• warmth, redness, or tingly feeling under your skin; or
• feeling weak or dizzy.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

Precautions

Patients should be told that the anti-anginal efficacy of isosorbide dinitrate is strongly related to its dosing regimen, so the prescribed schedule of dosing should be followed carefully. In particular, daily headaches sometimes accompany treatment with isosorbide dinitrate. In patients who get these headaches, the headaches are a marker of the activity of the drug. Patients should resist the temptation to avoid headaches by altering the schedule of their treatment with isosorbide dinitrate, since loss of headache may be associated with simultaneous loss of anti-anginal efficacy. Aspirin and/or acetaminophen, on the other hand, often successfully relieve isosorbide dinitrate-induced headaches with no deleterious effect on isosorbide dinitrate's anti-anginal efficacy.

Special information

The effects of Isordil in pregnancy have not been adequately studied. Isordil should be used only when the benefits of therapy clearly outweigh the potential risks to the developing baby. If you are pregnant or plan to become pregnant, inform your doctor immediately. It is not known if Isordil appears in breast milk; therefore, nursing mothers should use Isordil with caution.

Drug Interactions

Check the labels on all your medicines (e.g., cough-and-cold products, diet aids, nonsteroidal anti-inflammatory drugs-NSAIDs for pain/fever reduction) because they may contain ingredients that could increase your blood pressure, cause a fast heartbeat, or increase chest pain (e.g., pseudoephedrine, phenylephrine, chlorpheniramine, diphenhydramine, clemastine, ibuprofen, naproxen). Ask your pharmacist about the safe use of those products.

This product can affect the results of a certain lab test (serum cholesterol). Make sure laboratory personnel and all your doctors know you use this drug.