Usage
- Milk of Magnesia is prescribed for the relief of occasional constipation and to treat symptoms of heartburn, upset stomach, and acid indigestion.
- Pharmacological Classification: Saline laxative and antacid.
- Mechanism of Action: As a laxative, Milk of Magnesia works by drawing water into the intestines, softening the stool and promoting bowel movements. As an antacid, it neutralizes stomach acid.
Alternate Names
- Magnesium hydroxide
- Magnesium milk
- Brand Names: Phillips’ Milk of Magnesia, Milk of Magnesia (various manufacturers)
How It Works
- Pharmacodynamics: Milk of Magnesia acts as an osmotic laxative by increasing osmotic pressure within the intestinal lumen, drawing water into the bowel, and stimulating peristalsis. As an antacid, it neutralizes gastric acid, increasing the pH of stomach contents. This action relieves the symptoms of heartburn and acid indigestion.
- Pharmacokinetics: Orally administered magnesium hydroxide is poorly absorbed systemically. The unabsorbed portion exerts its laxative effect within the intestine. Some absorption of magnesium ions can occur, especially with higher doses or frequent use. Absorbed magnesium is primarily excreted by the kidneys.
- Mode of Action: In constipation, the osmotic action of Milk of Magnesia increases water content in the stool and stimulates intestinal motility. In heartburn, it directly neutralizes gastric hydrochloric acid. No receptor binding, enzyme inhibition, or neurotransmitter modulation are involved in its primary mechanisms of action.
- Elimination Pathways: Primarily renal excretion; unabsorbed magnesium is eliminated in feces.
Dosage
Standard Dosage
Adults:
- Constipation: 30-60 mL orally per day, preferably at bedtime.
- Antacid: 5-15 mL orally with water, up to four times a day. Do not exceed 60 mL in a 24-hour period.
Children:
- Constipation (6-11 years): 15-30 mL orally per day.
- Constipation (2-5 years): 5-15 mL orally per day.
- Constipation (under 2 years): Consult a doctor.
- Antacid (under 12 years): Consult a doctor.
Special Cases:
- Elderly Patients: Start with the lower end of the dose range and adjust as needed. Monitor renal function.
- Patients with Renal Impairment: Avoid Milk of Magnesia due to the risk of magnesium accumulation and toxicity.
- Patients with Hepatic Dysfunction: Dose adjustment may not be necessary, but caution is advised.
- Patients with Comorbid Conditions: Consider underlying conditions and potential drug interactions.
Clinical Use Cases
Milk of Magnesia is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU, or emergency situations. It is primarily indicated for outpatient management of occasional constipation and heartburn.
Dosage Adjustments
- Dose adjustments should be made in elderly patients and patients with renal impairment.
- Consider comorbidities and drug interactions that may impact dosing.
Side Effects
Common Side Effects
- Diarrhea
- Abdominal cramping
- Nausea
Rare but Serious Side Effects
- Rectal bleeding
- Symptoms of hypermagnesemia (muscle weakness, slow/irregular heartbeat, slow/shallow breathing, mental status changes)
- Dehydration
Long-Term Effects
- Electrolyte imbalances with chronic overuse
Adverse Drug Reactions (ADR)
- Hypermagnesemia
- Dehydration
Contraindications
- Hypersensitivity to magnesium hydroxide
- Renal failure or severe renal impairment
- Appendicitis or symptoms suggestive of appendicitis
- Bowel obstruction
Drug Interactions
Milk of Magnesia can interact with numerous medications, including antibiotics, bisphosphonates, digoxin, and tetracyclines. It can decrease the absorption of many orally administered drugs. Consult a drug interaction resource for a comprehensive list.
Pregnancy and Breastfeeding
- Limited data are available on the use of Milk of Magnesia during pregnancy. Consult a doctor before use.
- Small amounts of magnesium may be excreted in breast milk. Consult a doctor before use while breastfeeding.
Drug Profile Summary
- Mechanism of Action: Osmotic laxative, antacid.
- Side Effects: Diarrhea, cramping, nausea, hypermagnesemia (rare).
- Contraindications: Hypersensitivity, renal failure, appendicitis, bowel obstruction.
- Drug Interactions: Numerous drug interactions; consult a comprehensive resource.
- Pregnancy & Breastfeeding: Consult a doctor before use.
- Dosage: See dosage section.
- Monitoring Parameters: Serum magnesium levels (with prolonged use or high doses), renal function.
Popular Combinations
Milk of Magnesia is often used alone.
Precautions
- General Precautions: Assess for allergies, renal function, and bowel habits before use.
- Specific Populations: Consult a doctor before using in pregnancy, breastfeeding, or in patients with renal impairment.
- Lifestyle Considerations: No specific lifestyle restrictions are typically associated with Milk of Magnesia.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Milk Of Magnesia?
A: Refer to the detailed dosage section above, considering age and specific medical conditions.
Q2: How quickly does Milk of Magnesia work for constipation?
A: Milk of Magnesia typically produces a bowel movement within 30 minutes to 6 hours.
Q3: Can I take Milk of Magnesia every day?
A: It is not recommended for long-term daily use. Consult a doctor if constipation persists.
Q4: What are the signs of a Milk of Magnesia overdose?
A: Symptoms of hypermagnesemia, such as muscle weakness, nausea, vomiting, slow heartbeat, and difficulty breathing.
Q5: Who should not take Milk of Magnesia?
A: Individuals with renal failure, appendicitis, bowel obstruction, or hypersensitivity to magnesium hydroxide.
Q6: Can I take Milk of Magnesia while pregnant?
A: Consult your doctor before using Milk of Magnesia during pregnancy. Safety data is limited.
Q7: Does Milk of Magnesia interact with other medications?
A: Yes, Milk of Magnesia can interact with many medications. Consult your doctor or pharmacist about potential interactions.
Q8: How should Milk of Magnesia be stored?
A: Store at room temperature, away from excessive heat and moisture. Do not freeze.
Q9: What should I do if I miss a dose of Milk of Magnesia for constipation?
A: If you miss a dose, take it as soon as you remember. If it is close to the time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not double the dose to catch up.
