ADMINISTRATION ROUTES:
IV
ALTERNATIVE NAMES:
Nipride, Nitropress
ICU INDICATIONS:
- Afterload reduction by peripheral vasodilation
- Treatment of hypertension
PRESENTATION AND ADMINISTRATION:
IV:
50 mg of powder in a vial. Add 2 - 3 mL of 5% glucose to dissolve the powder. Dilute reconstituted solution of 50 mg up to a total of 50 mL using 5% dextrose.
Sodium nitroprusside is ONLY compatible with 5% dextrose. No other drug may be co-administered via the side arm or added to the infusion while sodium nitroprusside is being infused.
Prepare all solutions immediately before use. Freshly prepared solution has a very faint brownish tinge. In aqueous solution, sodium nitroprusside is photosensitive and must be protected from light. Immediately after dilution the solution should be wrapped in aluminium foil to protect it from light. Use yellow tubing. It is not necessary to cover the tubing or the drip chamber with foil.
Any solution not used within 24 hours or preparation should be discarded. Any solution that is highly coloured should be discarded. Store at room temperature.
DOSAGE:
IV infusion:
0 - 20 mL/hr
DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:
Dose as in normal renal function; avoid prolonged use
DOSAGE IN PAEDIATRICS:
IV infusion:
Weight < 30 kg
3 mg/kg in 50 mL 5% dextrose at 0.5 - 4 mL/hr (0.5 - 4 mcg/kg/min)
Weight ≥ 30 kg
3 mg/kg in 100 mL 5% dextrose at 1 - 8 mL/hr (0.5 - 4 mcg/kg/min)
CLINICAL PHARMACOLOGY:
The principal pharmacological action of sodium nitroprusside is relaxation of vascular smooth muscle and consequent dilation of peripheral arteries and veins. Other smooth muscle is unaffected. Sodium nitroprusside has more activity on veins than arteries. Venous dilatation promotes peripheral blood pooling, so reducing venous return. This reduces left ventricular end diastolic pressure and pulmonary capillary wedge pressure (preload). Afterload reduction occurs due to decreased systemic vascular resistance.
CONTRAINDICATIONS:
- Known hypersensitivity to sodium nitroprusside
WARNINGS:
Methaemoglobinaemia
Patients receiving more than 10 mg/kg of sodium nitroprusside may develop methaemoglobinaemia. Signs & symptoms vary with degree of toxicity. Symptoms associated with a level > 10% include headache, fatigue, cyanosis, dizziness. Symptoms associated with a level > 50% include seizures and coma. Patients with co-morbidities may experience symptoms at levels as low as 5%. If suspected, sodium nitroprusside should be stopped, another agent commenced, and, if levels confirm toxicity, prompt treatment with supplemental oxygen & methylene blue commenced.
Cyanide Poisoning
When given faster than 2 mcg/kg/min, sodium nitroprusside may generate cyanide faster than it can be eliminated. This can lead to toxic, potentially lethal levels, especially in those with impaired renal function. This is more likely after prolonged, rapid infusions. If suspected, sodium nitroprusside should be stopped immediately and specific treatment commenced.
Excessive Hypotension
Sodium nitroprusside can cause precipitous decreases in blood pressure. Because sodium nitroprusside's hypotensive effect is very rapid in onset and in dissipation, small variations in infusion rate can lead to wide, undesirable variations in blood pressure.
PRECAUTIONS:
General:
Sodium nitroprusside may lead to severe hypotension in patients with haemodynamically significant aortic stenosis.
Laboratory Tests:
No tests in addition to routine ICU tests are required. If suspected, methaemoglobin levels should be measured.
Drug/Laboratory Test Interactions:
None of note
IMPORTANT DRUG INTERACTIONS IN ICU:
Amplification of the vasodilatory effects of sodium nitroprusside by sildenafil can result in severe hypotension. Additive effects may be observed when sodium nitroprusside is combined with other antihypertensives.
ADVERSE REACTIONS:
General:
Allergic reactions
Cardiovascular:
Tachycardia, hypotension, syncope, rebound hypertension, palpitations
Gastrointestinal:
Nausea, vomiting, abdominal pain
Neurological:
Headache
Haematological:
Methaemoglobinaemia, thiocyanate toxicity