Neophyr (Nitric Oxide)

Neophyr delivers inhaled nitric oxide to target the pulmonary vasculature, addressing conditions characterized by elevated pulmonary arterial pressure.

• Persistent pulmonary hypertension of the newborn (PPHN): improves oxygenation by selectively dilating pulmonary vessels.
• Acute respiratory distress syndrome (ARDS): reduces pulmonary artery pressure and may enhance gas exchange.
• Pulmonary hypertension in adults: lowers pulmonary vascular resistance and supports right‑ventricular function.

• Inhaled nitric oxide diffuses into vascular smooth‑muscle cells of the pulmonary circulation, where it activates soluble guanylate cyclase. This enzyme catalyzes the conversion of GTP to cyclic GMP, leading to smooth‑muscle relaxation, vasodilation of pulmonary vessels, and improved ventilation‑perfusion matching without systemic hypotension.

Inhaled nitric oxide may be associated with a range of adverse reactions, from mild to severe.

Common Side Effects

• Headache: transient, often related to systemic absorption.
• Hypotension: mild systemic blood pressure reduction.
• Methemoglobinemia: elevated methemoglobin levels causing reduced oxygen delivery.
• Cough or throat irritation: local airway discomfort.
• Nausea: occasional gastrointestinal upset.

Serious or Rare Side Effects

• Rebound pulmonary hypertension: sudden rise in pulmonary pressure after abrupt discontinuation.
• Severe hypotension: marked drop in systemic blood pressure requiring intervention.
• Bleeding: increased risk when combined with anticoagulants.
• Renal dysfunction: rare reports of acute kidney injury.
• Pulmonary edema: fluid accumulation in the lungs.
• Allergic reactions: rash, pruritus, or anaphylaxis.

When prescribing inhaled nitric oxide, clinicians should consider several safety measures.

• Pregnancy: safety not established; use only if benefits outweigh risks.
• Breastfeeding: insufficient data; caution advised.
• Methemoglobinemia monitoring: measure methemoglobin levels regularly.
• Concomitant vasodilators: avoid additive hypotensive effects.
• Discontinuation: taper or wean to prevent rebound pulmonary hypertension.
• Store at ambient temperature: keep cylinders upright, protect from heat and direct sunlight.

Nitric oxide can interact with other agents that affect vascular tone or blood components.

Major Interactions (Avoid)

• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): may cause severe hypotension.
• Other pulmonary vasodilators (e.g., prostacyclin analogues): additive blood pressure lowering.
• Methylene blue: can antagonize nitric oxide’s effect.

Moderate Interactions (Monitor Closely)

• Anticoagulants: increased bleeding risk.
• Inhaled anesthetics: may alter hemodynamic response.
• High inspired oxygen concentrations: can reduce nitric oxide stability.
• Certain antibiotics (e.g., sulfonamides): potential for methemoglobinemia enhancement.