FOR INTRAVENOUS USE ONLY. NOT FOR DIRECT INTRAVENOUS INJECTION. NITROGLYCERIN INJECTION MUST BE DILUTED IN DEXTROSE (5%) INJECTION OR SODIUM CHLORIDE (0.9%) INJECTION PRIOR TO ITS INFUSION (SEE DOSAGE AND ADMINISTRATION SECTION). THE ADMINISTRATION SET USED FOR INFUSION WILL AFFECT THE AMOUNT OF NITROGLYCERIN INJECTION DELIVERED TO THE PATIENT. (SEE WARNINGS, AND DOSAGE AND ADMINISTRATION SECTIONS).
SEVERAL PREPARATIONS OF NITROGLYCERIN FOR INJECTION ARE AVAILABLE. THEY DIFFER IN CONCENTRATION AND/OR VOLUME PER VIAL. WHEN SWITCHING FROM ONE PRODUCT TO ANOTHER, ATTENTION MUST BE PAID TO THE DILUTION AND DOSAGE AND ADMINISTRATION INSTRUCTIONS.
Nitroglycerin is 1,2,3-propanetriol trinitrate, an organic nitrate whose structural formula is:
whose empiric formula is C3H5N3O9, and whose molecular weight is 227.09. The organic nitrates are vasodilators, active on both arteries and veins.
Nitroglycerin Injection, USP is a clear, practically colorless additive solution for intravenous infusion after dilution. Each mL contains: Nitroglycerin 5 mg, Alcohol 30% (v/v), Propylene Glycol 30%, and Water for Injection q.s. pH (range 3.0 to 6.5) may have been adjusted with Sodium Hydroxide and/or Hydrochloric Acid.
The solution is sterile, non-pyrogenic, and nonexplosive.
The principal pharmacological action of Nitroglycerin Injection 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.
Dosing regimens for most chronically used drugs are designed to provide plasma concentrations that are continuously greater than a minimally effective concentration. This strategy is inappropriate for organic nitrates. Several well-controlled clinical trials have used exercise testing to assess the anti-anginal efficacy of continuously-delivered nitrates. In the large majority of these trials, active agents were indistinguishable from placebo after 24 hours (or less) of continuous therapy. Attempts to overcome nitrate tolerance by dose escalation, even to doses far in excess of those used acutely, have consistently failed. Only after nitrates have been absent from the body for several hours has their anti-anginal efficacy been restored.
Nitroglycerin Injection is indicated for treatment of peri-operative hypertension; for control of congestive heart failure in the setting of acute myocardial infarction; for treatment of angina pectoris in patients who have not responded to sublingual nitroglycerin and β-blockers; and for induction of intraoperative hypotension.
Allergic reactions to organic nitrates are extremely rare, but they do occur. Nitroglycerin Injection is contraindicated in patients who are allergic to it.
In patients with pericardial tamponade, restrictive cardiomyopathy, or constrictive pericarditis, cardiac output is dependent upon venous return. Intravenous nitroglycerin is contraindicated in patients with these conditions.
Amplification of the vasodilatory effects of nitroglycerin by sildenafil can result in severe hypotension. The time course and dose dependence of this interaction have not been studied. Appropriate supportive care has not been studied, but it seems reasonable to treat this as a nitrate overdose, with elevation of the extremities and with volume expansion.
Nitroglycerin readily migrates into many plastics, including the polyvinyl chloride (PVC) plastics commonly used for intravenous administration sets. Nitroglycerin absorption by PVC tubing is increased when the tubing is long, the flow rates are low, and the nitroglycerin concentration of the solution is high. The delivered fraction of the solution's original nitroglycerin span has been 20-60% in published studies using PVC tubing; the fraction varies with time during a single infusion, and no simple correction factor can be used. PVC tubing has been used in most published studies of intravenous nitroglycerin, but the reported doses have been calculated by simply multiplying the flow rate of the solution by the solution's original concentration of nitroglycerin. The actual doses delivered have been less, sometimes much less, than those reported.
Some in-line intravenous filters also absorb nitroglycerin; these filters should be avoided.
Because of the problem of nitroglycerin absorption by polyvinyl chloride (PVC) tubing, Nitroglycerin Injection should be used with the least absorptive infusion tubing (i.e., non-PVC tubing) available.
DOSING INSTRUCTIONS MUST BE FOLLOWED WITH CARE. WHEN THE APPROPRIATE INFUSION SETS ARE USED, THE CALCULATED DOSE WILL BE DELIVERED TO THE PATIENT, BECAUSE THE LOSS OF NITROGLYCERIN INJECTION SEEN WITH STANDARD PVC TUBING WILL BE AVOIDED. THE DOSAGES REPORTED IN PUBLISHED STUDIES UTILIZED GENERAL-USE PVC ADMINISTRATION SETS, AND RECOMMENDED DOSES BASED ON THIS EXPERIENCE WILL BE TOO HIGH WHEN THE LOW-ABSORBING INFUSION SETS ARE USED.
Adverse reactions to nitroglycerin are generally dose-related and almost all of these reactions are the result of nitroglycerin's activity as a vasodilator. Headache, which may be severe, is the most commonly reported side effect. Headache may be recurrent with each daily dose, especially at higher doses. Transient episodes of lightheadedness, occasionally related to blood pressure changes, may also occur. Hypotension occurs infrequently, but in some patients it may be severe enough to warrant discontinuation of therapy. Syncope, crescendo angina, and rebound hypertension have been reported but are uncommon.
Extremely rarely, ordinary doses of organic nitrates have caused methemoglobinemia in normal-seeming patients. Methemoglobinemia is so infrequent at these doses that further discussion of its diagnosis and treatment is deferred (see OVERDOSAGE).
NOT FOR DIRECT INTRAVENOUS INJECTION
NITROGLYCERIN INJECTION IS A CONCENTRATED, POTENT DRUG WHICH MUST BE DILUTED IN DEXTROSE (5%) INJECTION OR SODIUM CHLORIDE (0.9%) INJECTION PRIOR TO ITS INFUSION. NITROGLYCERIN INJECTION SHOULD NOT BE MIXED WITH OTHER DRUGS.
Note: If the concentration is adjusted, it is imperative to flush or replace the infusion set before a new concentration is utilized. If the set were not flushed or replaced, it could take minutes to hours, depending upon the flow rate and the dead space of the set, for the new concentration to reach the patient.
Invert the glass parenteral bottle several times to assure uniform dilution of the nitroglycerin.
Dosage is affected by the type of container and administration set used. See WARNINGS.
Although the usual starting adult dose range reported in clinical studies was 25 mcg/min or more, these studies used PVC administration sets. THE USE OF NON-ABSORBING TUBING WILL RESULT IN THE NEED FOR REDUCED DOSES.
If a peristaltic action infusion pump is used, an appropriate administration set should be selected with a drip chamber that delivers approximately 60 microdrops/mL. Table 1 and the Nitroglycerin Injection Dilution Table below may be used to calculate the nitroglycerin dilution and flow rate in microdrops/minute to achieve the desired Nitroglycerin Injection administration rate.
If a volumetric infusion pump is used, an appropriate volumetric infusion pump connector set should be selected. Table 1 below may still be used; however, flow rate will be determined directly by the infusion pump, independent of the drop size of the appropriate set drip chambers. Thus, the reference to ``microdrops/min′′ is not applicable, and the corresponding flow rate in mL/hr should be used to determine pump settings.
When using a non-absorbing infusion set, the initial dosage should be 5 mcg/min delivered through an infusion pump capable of exact and constant delivery of the drug. Subsequent titration must be adjusted to the clinical situation, with dose increments becoming more cautious as partial response is seen. Initial titration should be in 5 mcg/min increments, with increases every 3-5 minutes until some response is noted. If no response is seen at 20 mcg/min, increments of 10 and later 20 mcg/min can be used. Once a partial blood pressure response is observed, the dose increase should be reduced and the interval between increases should be lengthened.
Some patients with normal or low left ventricular filling pressures or pulmonary capillary wedge pressure (e.g., angina patients without other complications) may be hypersensitive to the effects of nitroglycerin and may respond fully to doses as small as 5 mcg/min. These patients require especially careful titration and monitoring.
There is no fixed optimum dose of nitroglycerin. Due to variations in the responsiveness of individual patients to the drug, each patient must be titrated to the desired level of hemodynamic function. Therefore, continuous monitoring of physiologic parameters (i.e., blood pressure and heart rate in all patients, other measurements such as pulmonary capillary wedge pressure, as appropriate) MUST be performed to achieve the correct dose. Adequate systemic blood pressure and coronary perfusion pressure must be maintained.
Nitroglycerin Injection is supplied in 5 mg/mL solution. A dilution and administration scheme for Nitroglycerin Injection is shown in Table 1 below.
60 MICRODROPS = 1 mL
|Dose (mcg/min)||FLOW RATE (microdrops/min = mL/hr)|
(Diluent: Dextrose 5% Injection or Sodium Chloride Injection (0.9%))
|Each mL of Nitroglycerin Injection contains 5 mg of nitroglycerin.|
|Total Contents:||Each 5 mL vial contains 25 mg of nitroglycerin.|
|Each 10 mL vial contains 50 mg of nitroglycerin.|
|mL of |
|100 mcg/mL||200 mcg/mL||400 mcg/mL|
|Volume||q.s. to||q.s. to||q.s. to|
|5 mL||25 mg||250 mL||125 mL||- - -|
|10 mL||50 mg||500 mL||250 mL||125 mL|
|20 mL||100 mg||1000 mL||500 mL||250 mL|
|40 mL||200 mg||- - -||1000 mL||500 mL|
NOTE: Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.
HOW SUPPLIED: Nitroglycerin Injection, USP, 5 mg/mL is available as follows:
|Product Number||Container Strength/Size||Packaged|
|NDC 0517-4805-25||5 mL single dose vial - 25 mg/5 mL||Boxes of 25|
|NDC 0517-4810-25||10 mL single dose vial - 50 mg/10 mL||Boxes of 25|
PROTECT FROM LIGHT. RETAIN IN CARTON UNTIL TIME OF USE.
Store at controlled room temperature 15°-30°C (59°-86°F) (See USP).
DISCARD UNUSED PORTION.
SHIRLEY, NY 11967