Introduction
Magnesium sulphate (MgSO4) is a versatile compound with wide-ranging clinical applications due to its physiological importance. In this article, we will explore its clinical uses, basic pharmacology, physiology, and potential toxicity.
Clinical Uses
| Clinical Condition | Mechanism of Action |
|---|---|
| Pre-eclampsia and Eclampsia | Reduces systemic vascular resistance, CNS excitability. |
| Tocolysis | Induces uterine relaxation. |
| Acute Arrhythmias | Effective in abolishing various arrhythmias. |
| Hypomagnesaemia | Corrects magnesium deficiency. |
| Tetanus | Treats muscle spasm and autonomic instability. |
| Epilepsy | Controls status epilepticus. |
| Subarachnoid Hemorrhage | Prevents cerebral vasospasm. |
| Asthma | Acts as a bronchodilator in severe refractory cases. |
| Analgesia | Used as an epidural adjunct for postoperative pain relief. |
| Constipation and Dyspepsia | Functions as a laxative and antacid. |
Pharmacology and Physiology
| Aspect of Magnesium | Function |
|---|---|
| Mode of Action | Acts as a natural calcium antagonist, inhibits Ca2+ influx. |
| Competes with calcium for binding sites on sarcoplasmic | |
| reticulum. Acts as an NMDA receptor antagonist. | |
| Physiology | Fourth most abundant cation in the body, important intracellular cation. |
| Activates over 300 enzyme systems. | |
| Affects neurons, myocardial and skeletal muscle, vasomotor | |
| tone, and hormone receptor binding. |
Effects on Systems
- Central and Peripheral Nervous Systems: Depresses CNS, sedating, cerebral vasodilator, interferes with neurotransmitter release, and affects muscle function.
- Cardiovascular: Reduces vascular tone, inhibits catecholamine release, decreases cardiac conduction, and contractile force.
- Respiratory: Weakens respiratory muscles, reduces bronchomotor tone.
- Uterus: Powerful tocolytic, useful in hypertensive disease of pregnancy.
- Renal: Acts as a vasodilator and diuretic.
Toxicity
| Magnesium Level (mmol/l) | Effects |
|---|---|
| 0.7–1.0 | Normal blood level. |
| 4.0–8.0 | Therapeutic level. |
| 15.0 | Respiratory paralysis. |
| 15.0 | Complete SAN and AV block. |
| 25.0 | Cardiac arrest. |
Magnesium can cross the placenta rapidly, potentially affecting the neonate, leading to hypotonia and apnea.
Conclusion
Magnesium sulphate is a vital compound in medical practice due to its diverse clinical applications, ranging from obstetrics to cardiology and neurology. Understanding its pharmacological properties, physiological roles, and potential toxicity is crucial for its safe and effective use in various medical scenarios.