Pharm II Exam 2: Magnesium Sulfate

Study Notes

Magnesium Sulfate (MgSO4) Overview

Therapeutic use for hypomagnesemia and eclampsia-related seizures.
Classified as an electrolyte and magnesium supplement.

Therapeutic Effects and Uses

Available in both oral (PO) and parenteral forms (IM, IV).
Rapid IV administration effectively treats severe hypomagnesemia; IM can cause significant pain.
Parenteral solutions include varying concentrations (4%, 8%, 12.5%, 50%).
Therapeutic effects appear within 30 to 60 minutes post-administration.
Monitoring of plasma magnesium levels is essential during treatment.
Oral magnesium sulfate is used as a cathartic; Epsom salt is often utilized in baths for muscle aches despite lacking scientific support.
Acts as a CNS depressant, useful for anticonvulsant effects in preeclampsia/eclampsia.
Off-label use includes slowing uterine contractions in preterm labor.

Mechanism of Action

Functions as a replacement for lost magnesium in the body.

Pharmacokinetics

Routes: PO, IM, IV; not absorbed via PO.
Widely distributed, crosses the placenta, found in breast milk.
Not metabolized; excretion is renal.
Onset of action: PO (1-2 hours), IM (1 hour), IV (immediate).
Duration: PO/IM (3-4 hours), IV (30 minutes); half-life unknown.

Adverse Effects

Close monitoring necessary during IV infusions to prevent toxicity.
Signs of overdose: flushing, sedation, confusion, increased thirst, muscle weakness.
Severe overdose can lead to neuromuscular blockade, respiratory paralysis, heart block, and circulatory collapse.
Mild to moderate hypomagnesemia treated with oral magnesium forms.
Oral magnesium sulfate may cause diarrhea.

Contraindications and Precautions

Contraindicated in patients with serious cardiac disease.
Not recommended for oral use in undiagnosed abdominal pain, intestinal obstruction, or fecal impaction.
Caution in patients with chronic kidney disease (CKD) due to risk of toxic levels.

Drug Interactions

Increased respiratory depression and apnea risks when used with neuromuscular blockers.
Enhanced sedation potential when combined with other CNS depressants.
Magnesium salts may inhibit the absorption of certain anti-infectives like tetracycline.

Pregnancy Considerations

Classified as a Category A drug, indicating no known risks during pregnancy.

Treatment of Overdose

Overdose may result in serious respiratory and cardiac suppression.
IV administration of calcium gluconate or gluceptate acts as an antidote.

Similar Drugs

OTC oral magnesium salts include magnesium citrate (laxative) and magnesium hydroxide (milk of magnesia).
Magnesium oxide (Mag-Ox) serves as an antacid.
Magnesium salicylate (Doan's Pills) used for analgesic purposes.

Description

This quiz focuses on the prototype drug Magnesium Sulfate (MgSO4), covering its classification, therapeutic effects, and primary uses. Perfect for those studying pharmacology and techniques for treating hypomagnesemia and eclamptic seizures.