Emergency Asthma Medicines

Emergency asthma medicines relieve airway narrowing in acute severe and life-threatening asthma. Treatment combines oxygen, repeated inhaled bronchodilators and early systemic corticosteroids, with magnesium or other agents for poor response. Peak flow, oxygen saturation and the ability to speak guide severity, and a silent chest or exhaustion means life-threatening disease.

Classification. Short-acting beta-2 agonists (salbutamol, terbutaline); anticholinergics (ipratropium); corticosteroids (prednisolone, hydrocortisone); magnesium sulfate; methylxanthines (aminophylline); adrenaline and ketamine in refractory cases.

Mechanism. Beta-2 agonists relax airway smooth muscle. Ipratropium blocks muscarinic receptors. Corticosteroids reduce airway inflammation over hours. Magnesium relaxes smooth muscle by blocking calcium entry.

Pharmacokinetics. Nebulised salbutamol acts in 5 minutes and lasts 3 to 4 hours. Oral prednisolone acts in 4 to 6 hours. Aminophylline has a narrow therapeutic range and many interactions.

Signs of life-threatening asthma. Peak flow under 33% of best, oxygen saturation under 92%, silent chest, cyanosis, poor respiratory effort, arrhythmia, exhaustion or confusion.

Discharge. Continue prednisolone, give inhaled corticosteroid, check inhaler technique, and arrange follow-up within 48 hours to 1 week.

Avoid. Sedatives, mucolytics in the acute attack and routine antibiotics.

• First-line. Oxygen, repeated salbutamol, early oral steroid.
• Alternative. Hydrocortisone intravenously; terbutaline subcutaneously.
• Specialist. Aminophylline, ketamine, non-invasive ventilation, intubation with careful ventilation, extracorporeal support.
• Emergency. Severe or life-threatening asthma, or no response to initial treatment within 15 to 30 minutes.

Selection. Add ipratropium for severe attacks. Give magnesium early for life-threatening asthma. Reassess every 15 to 30 minutes.

Contraindications. Beta-2 agonists: none in an acute attack (caution in arrhythmia). Magnesium: severe kidney failure, heart block. Aminophylline: seizure disorder, recent theophylline use.

Serious adverse effects.

• Tremor, tachycardia, low potassium and raised lactate with salbutamol.
• Dry mouth and urinary retention with ipratropium.
• Hyperglycaemia, mood change and fluid retention with steroids.
• Aminophylline: arrhythmia, seizures and vomiting.

Major interactions. Beta-blockers block bronchodilators; loop and thiazide diuretics and steroids add to hypokalaemia; aminophylline with ciprofloxacin, erythromycin and rifampicin (levels change); magnesium with neuromuscular blockers.

Common prescribing errors.

• Giving too little salbutamol or giving it too slowly.
• Delaying steroids.
• Using high-flow oxygen to normalise saturation in a patient who also has COPD.
• Giving sedatives to a restless, hypoxic patient.
• Discharging without steroids, an inhaler plan or follow-up.

Special groups.

• Pregnancy: use the usual adult drugs; hypoxia harms the fetus more than the drugs.
• Breastfeeding: compatible.
• Children: weight and age-based doses; early steroid; oxygen; severe attacks need specialist input.
• Older adults: check for heart failure or COPD; lower aminophylline doses.
• Kidney: caution with magnesium.
• Liver: lower aminophylline doses.
• East Africa: salbutamol, prednisolone and oxygen are the main available options, though nebulisers and oxygen supply may be limited; spacers can be made from a plastic bottle; consider tuberculosis, HIV-related lung disease and pneumonia when wheeze is new, and avoid giving beta-blockers to anyone with wheeze.

Monitoring. Peak flow, oxygen saturation, respiratory rate, heart rate, potassium, blood gas in severe cases and chest X-ray for suspected pneumothorax or pneumonia.

Referral and escalation. Life-threatening features, no improvement after 15 to 30 minutes, rising carbon dioxide, exhaustion, or need for ventilation.

Comparison with alternative classes. Inhaled beta-2 agonists work fastest and are first-line. Steroids prevent relapse and deterioration. Magnesium, aminophylline and ketamine help only in refractory cases.