SODIUM NITROPRUSSIDE: MIX VASODILATOR
GENERAL DESCRIPTION
Sodium Nitroprusside is a complex of iron, cyanide groups, and a nitroso moiety. It is also known as glyceryl nitrate (GTN). It is a powerful parenterally administered nitro vasodilator. It dilates both arterial and venous vessels unlike other nitrates.
GENERIC NAME: Sodium nitroprusside
BRAND NAME: Nitropress
MECHANISM OF ACTION
Nitrodilators are divided into two types according to the release of NO
- release NO spontaneously
- require enzymes to form NO.
Sodium nitroprusside is a prodrug and need to be denitrated. Nitroprusside release NO promptly without the need of enzymes. It binds to the oxyhemoglobin and release cyanide, methemoglobin and nitric oxide. This nitric oxide is potent activator of guanylyl cyclase enzyme (GC) which is soluble in smooth muscle. This guanylyl cyclase (GC) convert GTP into cGMP. This intracellular cGMP block the calcium to enter into the cells tends to decrease the calcium levels in the cells which then cause smooth muscles relaxation. The cGMP also activates protein kinase C (PKC) which further activates phosphatase enzymes. This phosphatase inactivates myosin light chain which further take part in relaxation of smooth muscles. Sodium nitroprusside dilates both arteries and veins without producing effects on other vessels. These actions tend to decrease the venous return by increase venous capacitance. Arterial pressure also decreases. This decrease the cardiac output and myocardial oxygen demand.
PHARMACOKINETICS
It is taken as IV and onset of action is 1 min after infusion. The effect is diminished after 1-10 min after discontinuation. It is rapidly metabolized by uptake into red blood cell with the liberation of cyanide. Cyanide is converted into less toxic thiocyanate by mitochondrial enzyme and is eliminated by kidney. It is photosensitive and make up fresh before each administration and covered with opaque foil.
INDICATIONS
Hypertensive emergencies
Heart failure
Myocardial infarction
Angina pectoris
CONTRAINDICATIONS
Renal failure
Kidney failure
Anemia
Poor cerebral circulation
Vit B12 deficiency
SIDE EFFECTS & ADVERSE EFFECTS
Postural hypotension
Tachycardia
Accumulation of cyanide may cause:
Metabolic acidosis
Arrhythmia
Excessive hypotension
Weakness
Disorientation
Psychosis
Muscle spasm
Convulsion
Delayed hypothyroidism
DRUG INTERACTION
Phosphodiesterase type-5 inhibitors potentiate the hypotensive effects of sodium nitroprusside and may cause myocardial infarction. Therefore these drugs are contraindicated with sodium nitroprusside.
Antihypertensive drugs may cause severe hypotension when given with sodium nitroprusside
NURSING INTERVENTION
Enquire the complete health history of the patient including allergy, drug interactions, and family background of hypertension.
Monitor blood pressure and pulse before and during treatment.
Check lab test for CBC, blood glucose, BUN, creatinine, platelets, electrolytes, LFT
Arterial pressure should be monitored during treatment via intra-arterial recording.
Observe patients for possible s/s of edema or congestive heart failure.
PATIENT EDUCATION
Avoid taking alcohol while taking medicine.
Instruct the right dose and timings of medicine.
Inform the patients about the possible side effects
Advice to take care and slow change of posture due to dizziness and danger of fall or injuries
Medicine may cause dizziness, don’t drive or perform alertness activities.
Report health professional immediately if dermatological adverse effects seen.
Do not breast feed while taking the medicine.
Educate patient healthy life style choice to reduce hypertension such as dietary intake of sodium and cholesterol, exercise, smoking cessation etc.