Cromolyn Sodium

Cromolyn sodium (sodium cromoglicate) is a mast cell stabiliser used for prevention in allergic rhinitis, allergic conjunctivitis, exercise-induced bronchoconstriction and mild asthma, and orally in mastocytosis. It has no role in acute symptoms and works only with regular use.

Classification. Mast cell stabiliser, anti-allergic.

Mechanism. Prevents release of histamine and other mediators from sensitised mast cells and has a weak effect on sensory nerves and eosinophils.

Pharmacokinetics. Poorly absorbed: about 1% orally and 8% from the lung. Half-life 1 to 1.5 hours. Excreted unchanged in urine and bile.

Alternative, allergic rhinitis. Nasal spray 4%: 1 spray in each nostril 3 to 4 times daily, up to 6 times daily. Best started before allergen exposure. Benefit takes up to a week. Intranasal corticosteroid is more effective.

Alternative, allergic conjunctivitis. Eye drops 2%: 1 to 2 drops in each eye 4 times daily.

Alternative, asthma prophylaxis. Inhaler: 10 mg (2 puffs of 5 mg) 4 times daily, increased to 6 to 8 times daily if needed, then reduced to 3 times daily when control is established. Effect takes up to 4 weeks. Nebulised 20 mg 4 times daily where licensed. An inhaled corticosteroid is more effective.

Exercise-induced bronchoconstriction. 10 mg inhaled 15 minutes before exercise.

Specialist, systemic mastocytosis. Oral 200 mg four times daily, 30 minutes before meals and at bedtime in adults. Children 2 to 12 years: 100 mg four times daily, up to 40 mg/kg daily. Children under 2 years: specialist only.

Emergency. Not used.

Titration and loading. No loading dose.

Contraindications. Hypersensitivity.

Serious adverse effects. Rare anaphylaxis, eosinophilic pneumonia, angioedema.

Common adverse effects. Throat irritation, cough and transient bronchospasm with the inhaler. Sneezing and nasal irritation with the spray. Eye stinging with drops. Abdominal pain and headache orally.

Interactions. None of clinical importance.

Common prescribing errors. Using it for acute symptoms. Stopping early because benefit is slow. Using the eye drops with soft contact lenses when the product contains a preservative.

Special groups.

• Pregnancy: acceptable. Breastfeeding: compatible.

• Children: used from 5 years in asthma by inhaler, with a spacer; from 2 years for eye and nasal disease.

• Older adults: no adjustment.

• Kidney and liver impairment: reduce the dose in severe impairment.

• East Africa: availability is limited and usually confined to eye drops and nasal spray.

Formulations. Inhaler 5 mg/actuation, nebuliser solution 20 mg/2 mL, nasal spray 4%, eye drops 2%, oral solution 100 mg/5 mL.

Technique. Shake the inhaler and use a spacer. Blow the nose before the nasal spray. Remove soft contact lenses before eye drops and wait 15 minutes before reinserting.

Baseline. Symptom diary, spirometry in asthma.

Monitoring. Symptoms and reliever use. Review the need after 4 to 6 weeks and stop if there is no benefit.

Stop and reduce rules. Reduce frequency once symptoms are controlled. Stop for persistent bronchospasm or hypersensitivity. Therapeutic drug monitoring is not used.

Referral and escalation. Refer if asthma is not controlled or if mastocytosis is suspected.