Intervention: At randomization eligible patients were allocated to receive 2.5ml of isotonic magnesium sulphate (150 mg,245 mmol/L) on three occasional at 20 minutes interval or standard treatment 50 mg/kg intravenous magnesium sulphate. The asthma severity score was record at 0,20,40,60,120,180,240 minutes post randomization. Adverse event were assessed at each assessment point. Patients were followed up until discharge from hospital to collect secondary outcome data.
