Neophyr (Nitric Oxide)

Neophyr (inhaled nitric oxide) is used in the management of pulmonary vascular disorders.

• Persistent pulmonary hypertension of the newborn (PPHN): improves oxygenation by selectively dilating pulmonary vessels.
• Adult pulmonary arterial hypertension: reduces pulmonary arterial pressure and right‑ventricular workload.
• Acute respiratory distress syndrome (ARDS) as adjunct therapy: may enhance oxygenation when conventional measures are insufficient.

• Inhaled nitric oxide diffuses across the alveolar‑capillary membrane and enters vascular smooth‑muscle cells, where it activates soluble guanylate cyclase. This raises cyclic guanosine monophosphate (cGMP) levels, causing relaxation of pulmonary arterial smooth muscle and a selective reduction of pulmonary vascular resistance without systemic vasodilation. The rapid onset and short half‑life allow precise titration of pulmonary pressure.

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

Common Side Effects

• Methemoglobinemia: elevated methemoglobin levels reducing oxygen transport.
• Nitrogen dioxide formation: airway irritation from NO2.
• Transient hypotension: brief drop in systemic blood pressure.
• Headache: mild cephalic discomfort.

Serious or Rare Side Effects

• Severe methemoglobinemia: symptomatic levels requiring treatment.
• Rebound pulmonary hypertension: rapid increase in pulmonary pressure after abrupt cessation.
• Hemorrhage: increased bleeding risk in susceptible patients.

When using Neophyr, several precautions should be observed to ensure safety and efficacy.

• Monitor methemoglobin: regularly check blood levels to keep within safe limits.
• Measure nitrogen dioxide: maintain NO2 concentrations below recommended thresholds.
• Titrate dosage carefully: adjust inhaled concentration based on patient response.
• Avoid abrupt discontinuation: wean the gas to prevent rebound pulmonary hypertension.
• Contraindications: not recommended in patients with severe anemia or methemoglobin‑inducing disorders.
• Store at ambient temperature: keep in original container, protect from moisture and direct sunlight.

Inhaled nitric oxide can interact with other medications, affecting its safety profile.

Major Interactions (Avoid)

• Phosphodiesterase‑5 inhibitors (e.g., sildenafil): additive pulmonary vasodilation may cause severe hypotension.
• Other inhaled pulmonary vasodilators (e.g., prostacyclin analogues): risk of excessive vasodilation and rebound hypertension.
• Methylene blue: may interfere with methemoglobin reduction therapy.

Moderate Interactions (Monitor Closely)

• General anesthetics (e.g., volatile agents): may potentiate hypotensive effects.
• Oxygen therapy at high concentrations: can increase nitrogen dioxide formation.
• Anticoagulants: monitor for increased bleeding risk.