Schedule H

Intravenous (IV only)

• Injection: 50 mg vial (powder for reconstitution)

Note: Solution must be prepared fresh; protect from light using amber-coloured or opaque infusion sets.

INDICATIONS + DOSING — FOR CLINICIAN USE ONLY

Primary Indications (Approved / Standard in India)

1. Hypertensive Emergencies / Malignant Hypertension

Parameter Recommendation

Starting dose 0.3 mcg/kg/min IV infusion

Titration Increase by 0.5 mcg/kg/min every 3–5 minutes based on BP response

Usual maintenance dose 0.5–6 mcg/kg/min

Maximum dose 10 mcg/kg/min (for ≤10 minutes only)

Clinical Notes:

• Continuous intra-arterial BP monitoring is mandatory

• Dilute only in 5% Dextrose (D5W); do NOT use normal saline

• Protect infusion from light at all times

• Onset of action: 30 seconds to 2 minutes

• Duration of effect: 1–10 minutes after stopping infusion

1. Acute Decompensated Heart Failure (ADHF) with Elevated SVR — Specialist Only

Parameter Recommendation

Starting dose 0.3–0.5 mcg/kg/min IV infusion

Titration Adjust based on haemodynamic parameters (cardiac output, SVR, PCWP)

Usual maintenance dose 0.5–5 mcg/kg/min

Maximum dose 8 mcg/kg/min

Clinical Notes:

• Use only in ICU/CCU with invasive haemodynamic monitoring

• Often combined with inotropes (e.g., dobutamine)

• Avoid in patients with acute MI without adequate preload optimisation

1. Controlled Hypotension During Surgery — Specialist Anaesthesia Use

Parameter Recommendation

Starting dose 0.5 mcg/kg/min IV infusion

Titration Adjust to achieve target mean arterial pressure for surgical field

Usual maintenance dose 0.5–5 mcg/kg/min

Maximum dose 10 mcg/kg/min (for ≤10 minutes only)

Clinical Notes:

• Requires continuous arterial BP monitoring

• Coordinate closely with surgical team

• Monitor for signs of organ hypoperfusion

Secondary Indications — Adults (Off-label)

Indication Dose Duration Notes

Aortic Dissection (OFF-LABEL) Starting: 0.3 mcg/kg/min; Titration: up to 6 mcg/kg/min; Target SBP 100–120 mmHg Until definitive management Specialist only; MUST be used with IV beta-blocker (esmolol/labetalol) to prevent reflex tachycardia; based on international consensus and Indian tertiary ICU practice (AIIMS, PGI protocols)

PAEDIATRIC DOSING (Specialist Only)

Primary Indications

Hypertensive Emergencies (PICU/NICU Setting Only)

Parameter Recommendation

Age group Neonates to adolescents

Starting dose 0.3–0.5 mcg/kg/min IV infusion

Titration Increase every 5–10 minutes as needed

Usual maintenance dose 0.5–5 mcg/kg/min

Maximum dose 10 mcg/kg/min (avoid exceeding; limit duration to <10 minutes at max rate)

Monitoring Required:

• Continuous arterial BP monitoring mandatory

• Monitor acid-base status frequently

• Serum thiocyanate levels if infusion >24–48 hours

• Watch for unexplained metabolic acidosis (cyanide toxicity)

Secondary Indications — Paediatrics (Off-label)

Indication Dose Notes

Controlled Hypotension During Paediatric Surgery (OFF-LABEL) 0.5–5 mcg/kg/min IV; titrate under anaesthetic supervision Specialist only; based on tertiary paediatric anaesthesia protocols

Age Restriction: Not recommended below 38 weeks corrected gestational age except under neonatal/paediatric intensivist supervision due to immature cyanide metabolism pathways.

Mild to moderate impairment No initial dose adjustment; monitor thiocyanate levels if infusion >24 hours

Severe impairment (eGFR <30) Avoid prolonged infusions; if essential, monitor thiocyanate levels frequently

Haemodialysis Not significantly cleared by dialysis; increased risk of thiocyanate accumulation

Peritoneal dialysis Use with caution; monitor for toxicity

• Known hypersensitivity to sodium nitroprusside

• Compensatory hypertension (e.g., coarctation of aorta, arteriovenous shunts)

• Leber's hereditary optic neuropathy

• Tobacco amblyopia

• Severe hepatic insufficiency

• Congenital optic atrophy

• Vitamin B12 deficiency (relative contraindication — impaired cyanide metabolism)

• Concurrent use with PDE5 inhibitors (sildenafil, tadalafil)

• Inadequate cerebral circulation where hypotension would be hazardous

• Renal impairment — increased risk of thiocyanate accumulation

• Prolonged infusions (>24–48 hours) — mandatory toxicity monitoring

• Hypothyroidism — thiocyanate inhibits iodide uptake; may worsen thyroid function

• Raised intracranial pressure — rapid BP reduction may compromise cerebral perfusion

• Hypovolaemia — correct volume depletion before initiation

• Elderly patients — increased sensitivity to hypotensive effects

• Anaemia — reduced oxygen-carrying capacity may exacerbate tissue hypoxia during hypotension

• Light exposure — solution degrades rapidly; use opaque infusion systems

• Avoid bolus administration — risk of severe, precipitous hypotension

Aspect Details

Safety Status Not routinely recommended; use only in life-threatening situations

Known Risks Fetal cyanide toxicity with prolonged maternal infusion; fetal bradycardia

Preferred Alternatives Labetalol IV, hydralazine IV (standard agents for hypertensive emergencies in Indian obstetric practice)

When to Use Only when preferred agents are contraindicated or ineffective; specialist input mandatory; limit duration

Monitoring Continuous fetal heart rate monitoring; maternal arterial BP; maternal acid-base status

Aspect Details

Compatibility Not well studied; avoid if possible during breastfeeding

Drug Levels in Milk Unknown; likely low with short-term use due to rapid metabolism

Preferred Alternatives Labetalol, nifedipine (if oral CCB needed)

Infant Monitoring If exposure unavoidable, observe infant for poor feeding, hypotonia, lethargy, signs of metabolic acidosis

Aspect Recommendation

Starting dose 0.1–0.3 mcg/kg/min IV infusion (lower end of range)

Titration Slower titration intervals; increase every 5–10 minutes

Special Risks Exaggerated hypotensive response, cerebral hypoperfusion, delirium, falls (post-ICU), reduced renal/hepatic reserve affecting toxin clearance

Additional Notes Close monitoring for cyanide/thiocyanate toxicity essential

Interacting Drug Effect/Risk Management

PDE5 inhibitors (sildenafil, tadalafil, vardenafil) Severe, potentially fatal hypotension Contraindicated; avoid concurrent use

General anaesthetics (propofol, inhalational agents) Profound additive hypotension Reduce nitroprusside dose; close haemodynamic monitoring

Other potent antihypertensives (IV labetalol, nitroglycerin) Additive severe hypotension Monitor closely; adjust doses

Hydroxocobalamin Binds cyanide; may reduce nitroprusside efficacy Avoid if possible; consider as antidote for toxicity, not concurrent therapy

Interacting Drug Effect/Risk Management

Nitrates (isosorbide dinitrate, GTN) Additive vasodilation and hypotension Dose reduction of one or both agents

Beta-blockers Additive hypotension; useful in aortic dissection to prevent reflex tachycardia Monitor HR and BP

Tricyclic antidepressants Enhanced hypotensive effects BP monitoring

Diuretics (furosemide) Additive BP lowering; minor antagonism of natriuresis Adjust diuretic dose if needed

ACE inhibitors / ARBs Additive hypotension Monitor closely

• Nausea and vomiting

• Headache

• Dizziness

• Diaphoresis

• Abdominal discomfort

• Palpitations

• Muscle twitching

• Flushing

• Hypotension (dose-related)

Adverse Effect Clinical Features Action Required

Cyanide toxicity Metabolic acidosis (increased lactate, decreased pH), altered sensorium, seizures, arrhythmias, tachyphylaxis to drug effect Immediate discontinuation; sodium thiosulphate or hydroxocobalamin as antidote; supportive care

Thiocyanate toxicity Fatigue, nausea, confusion, delirium, hypothyroidism, psychosis (chronic) Discontinue infusion; dialysis may help

Severe hypotension End-organ hypoperfusion (myocardial ischaemia, stroke, AKI) Stop infusion; IV fluids; vasopressors if needed

Methemoglobinaemia Cyanosis unresponsive to oxygen, chocolate-brown blood Discontinue; methylene blue if severe

Intracranial hypertension Cerebral vasodilation may worsen ICP Avoid in patients with raised ICP

During infusion Continuous arterial BP monitoring (mandatory); ECG monitoring; arterial blood gas every 4–6 hours

Infusion >24–48 hours Serum thiocyanate levels (maintain <10 mg/dL); serum cyanide if available; lactate levels

Signs of toxicity Unexplained metabolic acidosis, tachyphylaxis, altered mental status — suspect cyanide toxicity

Administration Notes:

• Dilute only in D5W (not normal saline)

• Use infusion pump with precise rate control

• Wrap infusion bag and tubing in opaque material to protect from light

• Freshly prepared solution should be used within 24 hours

• Nipress (Samarth Pharma)

• Nitropress (various)

• Sodium Nitroprusside IP (government supply)

Note: Limited brand availability; primarily stocked in tertiary care ICU formularies and government hospitals.

Note: Not currently under NPPA/DPCO price control. Available through government hospital supply chain and institutional pharmacy indents. Not routinely stocked in retail pharmacies.

1. Light protection is critical: Solution degrades within minutes when exposed to light, producing inactive and potentially toxic products — always use opaque tubing and covers.

1. Dilution medium: Use only 5% Dextrose (D5W) for dilution; normal saline causes degradation.

1. Toxicity threshold: If dose exceeds 10 mcg/kg/min for more than 10 minutes or total dose >1 mg/kg over short period, assume cyanide accumulation — monitor acid-base status urgently.

1. Tachyphylaxis = toxicity warning: Decreasing responsiveness to increasing doses suggests cyanide accumulation — do not simply increase dose; stop infusion and evaluate.

1. Antidote availability: Sodium thiosulphate (12.5 g IV over 10–15 min in adults) should be readily available in any ICU using nitroprusside; hydroxocobalamin is an alternative but has limited availability in India.

1. Aortic dissection protocol: Always combine with IV beta-blocker (esmolol preferred) before initiating nitroprusside to prevent reflex tachycardia and increased aortic shear stress.

Sodium Nitroprusside; hypertensive emergency; vasodilator; ICU drug; nitrovasodilator; cyanide toxicity; thiocyanate; controlled hypotension; specialist-only; critical care

RxIndia v1.0 — 01 Apr 2025

• Indian Pharmacopoeia (IP)

• National Formulary of India (NFI) 2021

• CDSCO approved formulations

• API Textbook of Medicine

• AIIMS Hospital Drug Formulary

• Tertiary hospital ICU protocols (AIIMS, PGIMER Chandigarh)

• Goodman & Gilman's The Pharmacological Basis of Therapeutics (supportive pharmacology reference)

• WHO Model Formulary (supportive reference for paediatric off-label use)