Duolaxin

Uses

Acid regurgitation, Constipation, Gastric ulcer, Gastrointestinal hyperacidity, Heartburn, Indigestion, Non ulcer dyspepsia, Osmotic laxative

Duolaxin is also used to associated treatment for these conditions: Acid indigestion, Colic, Constipation, Dyspepsia, Flatulence, Gastric Ulcer, Heartburn, Upset stomach, Antacid therapy, Gastric Acid Suppression

How Duolaxin works

The suspension of magnesium hydroxide is ingested and enters the stomach. According to the amount ingested, the magnesium hydroxide will either act as an antacid or a laxative.

Through the ingestion of 0.5-1.5 grams (in adults) the magnesium hydroxide will act by simple acid neutralization in the stomach. The hydroxide ions from the magnesium hydroxide suspension will combine with the acidic H+ ions of the hydrochloric acid made by the stomachs parietal cells. This neutralization reaction will result in the formation of magnesium chloride and water.

Through the ingestion of 2-5 grams (in adults) the magnesium hydroxide acts as a laxative in the colon. The majority of the suspension is not absorbed in the intestinal tract and will create an osmotic effect to draw water into the gut from surrounding tissues. With this increase of water in the intestines, the feces will soften and the intraluminal volume of the feces will increase. These effects still stimulate intestinal motility and induce the urge to defecate. Magnesium hydroxide will also release cholecystokinin (CKK) in the intestines which will accumulate water and electrolytes in the lumen and furthermore increase intestinal motility.

Dosage

Duolaxin dosage

Gastrointestinal hyperacidity:

• Adult: Up to 1 g daily, usually given in conjunction with an aluminium-containing antacid eg, aluminium hydroxide.

Osmotic laxative:

• Adult: 2.4-4.8 g daily as a single dose or in divided doses.
• Child: 6-11 yr: 1.2-2.4 g daily; 2-5 yr: 0.4-1.2 g daily. Doses may be given as a single dose or in divided doses.

Side Effects

GI irritation, diarrhoea, abdominal cramps; hypermagnesaemia (in patients with renal impairment). Paralytic ileus.

Toxicity

LD50=8500 mg/kg (rat, oral)

Common side effects include drowsiness or flushing (warmth, redness or tingly feeling).

Daily use of magnesium hydroxide can result in fluid and electrolyte disturbances.

Excessive use of the laxative effects of magnesium hydroxide may result in abdominal cramping, nausea and/or diarrhea.

In overdose, symptoms of gastrointestinal irritation and/or watery diarrhea may occur.

Magnesium hydroxide poisoning can result in hypermagnesemia which includes symptoms of: nausea, vomiting, flushing, thirst, hypotension, drowsiness, confusion, loss of tendon reflexes, muscle weakness, respiratory depression, cardiac arrhythmias, coma and cardiac arrest.

Not to be used in individuals with any form of kidney disease or renal failure, a magnesium restricted diet or with any sudden changes in bowel movement lasting over two weeks. Also not to be used in those individuals with abdominal pain, nausea, vomiting, symptoms of appendicitis or myocardial damage, heart block, fecal impaction, rectal fissures, intestinal obstruction or perforation or renal disease. Not to be used in women who are about to deliver as magnesium crosses the placenta and is excreted in small amounts in breast milk.

Using magnesium hydroxide with aluminum hydroxide can decrease the absorption rate of these drugs.

Magnesium hydroxide can react with digoxin, dicoumerol and cimetidine.

Use of ibuprofen with magnesium hydroxide can increase the absorption of the ibuprofen.

Use of magnesium hydroxide with penicallamine, bisphosphates, ketoconazole, quinolones or tetracycline can decrease the absorption of these drugs.

Enteric-coated tablets can be prematurely released when taken with magnesium hydroxide.

It is important to routinely monitor levels of serum magnesium and potassium in patients using magnesium hydroxide. Serum magnesium levels are necessary to determine how much magnesium is being absorbed and how much is being excreted by the kidneys. Excessive diarrhea can occur from use of magnesium hydroxide and thus it is important to also monitor serum potassium levels to ensure hypokalemia does not occur.

Precaution

Colostomy, ileostomy; electrolyte imbalance. Monitor for toxicity in patients with impaired renal function. Pregnancy.

Interaction

Decreases absorption of tetracyclines and biphosphonates. Separate administration of these and other drugs by around 2 hr.

Volume of Distribution

The peak action and distribution of magnesium hydroxide are variable.

Elimination Route

About 15%-50% of magnesium hydroxide is absorbed very slowly through the small intestine.

Half Life

N/A

Clearance

Magnesium hydroxide is mainly excreted in the urine by the kidneys. Since the kidneys play a major role in its clearance, individuals with renal failure are at risk of hypermagnesemia with long term consumption as the appropriate amounts of magnesium may not be excreted.

Elimination Route

After oral administration, up to 50% of the magnesium hydroxide suspension may be absorbed as magnesium ions through the small intestines and then rapidly excreted in the urine through the kidneys. The unabsorbed drug is mainly excreted in the feces and saliva.

Pregnancy & Breastfeeding use

Pregnancy category- A.

Contraindication

Intestinal obstruction, faecal impaction; renal failure; appendicitis.

Innovators Monograph

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