1. Overview of included studies.

Study ID	Study centres	Study location	Number randomised	Intervention	Comparison	Concomitant treatment	Hospitalisations in the last 12 months, n (%)	ICU admission in the last 12 months	Serum magnesium level: mean (SD)
Bajracharya 2021	Single	Nepal	172	Nebulised MgSO4 + Nebulised salbutamol	Placebo + nebulised salbutamol	Oxygen, ipratropium, hydrocortisone	NR	NR	NR
Comert 2016	Single	Turkey	20	Nebulised MgSO4 + standard care	Placebo + standard care	Oxygen, steroids, antibiotics and ipratropium	MgSO4: 3 (30) Placebo: 4 (40)	MgSO4: 0 Placebo: 0	NR
Edwards 2013	Two	New Zealand	116	Nebulised MgSO4 + Nebulised salbutamol	Placebo + nebulised salbutamol	Oxygen	MgSO4: 1 Placebo: 1.3	NR	mmol/L MgSO4: 0.81 (0.08) Placebo: 0.78 (0.10)
Hogg 2004	Single	UK	24	IV MgSO4 infusion	Placebo	NR	NR	NR	NR
Jahanian 2021	Single	Iran	60	IV MgSO4 infusion	Placebo	Oxygen, inhaled salbutamol and ipratropium, intravenous hydrocortisone	NR	NR	NR
Moradi 2021	Single	Iran	77	IV MgSO4 infusion	Placebo	Oxygen, nebulised salbutamol, nebulised ipratropium, IV hydrocortisone, IV antibiotics	NR	NR	NR
Mukerji 2015	Single	New Zealand	33	IV MgSO4 infusion	Placebo	Nebulised salbutamol	NR	NR	mmol/L MgSO4: 0.79 (0.1) Placebo: 0.78 (0.1)
Nouira 2014	Two	Tunisia	124	Nebulised MgSO4 + IV MgSO4 infusion	Nebulised ipratropium + IV normal saline	IV methyl prednisolone, antibiotics, and nebulised terbutaline	MgSO4: 3.6 (2.4) Ipratropium: 3.1 (1.7)	NR	NR
Pishbin 2018	Single	Iran	34	IV MgSO4 infusion + standard care	Placebo + standard care	NR	NR	NR	NR
Skorodin 1995	Two	USA	72	IV MgSO4 infusion	Placebo	Nebulised albuterol	NR	NR	mmol/L MgSO4: 0.94 (0.16) Placebo: 0.98 (0.16)
Solooki 2014	Single	Iran	30	IV MgSO4 infusion + standard treatment	Placebo + standard treatment	Bronchodilators, oxygen, corticosteroid and antibiotics	MgSO4: 9 (60) Placebo: 10 (67)	NR	mEq/L MgSO4: 2.11 (0.28) Placebo: 2.05 (0.40)

Abbreviations: MgSO₄: magnesium sulfate; NR: not reported