Not all laxatives work the same way, reports MayoClinic.com. Laxatives that contain magnesium hydroxide are meant to be taken on a short-term basis to encourage bowel movements or prevent constipation. Magnesium hydroxide, which may also go by the name of milk of magnesia, is classified as an oral osmotic.
Classification
Laxatives can be stimulants, bulk-formers, stool softeners, lubricants or a combination of two or more of these types. MayoClinic.com refers to magnesium hydroxide as a hyperosmotic. This oral laxative, which may come in tablet or liquid form, draws water into your bowels from your body tissues; increased water in the bowels makes stool softer and allows it to pass through your intestines a little easier. Magnesium hydroxide also decreases stomach acid and may be added to other over-the-counter antacids in smaller amounts.
Other Properties
Hyperosmotic laxatives can be one of three types: saline, lactulose or polymer. Magnesium hydroxide is a saline laxative; these particular laxatives are used when you want rapid effects, says MayoClinic. According to the label of one familiar name brand milk of magnesia laxative, bowel movements usually take place between a half-hour and six hours after taking the medication. Saline laxatives should not be used for a long duration or when constipation is a recurring problem.
Safety
Milk of magnesia should be used according to the directions on the label and for short periods of time. MayoClinic.com indicates that if you still have constipation after a week after using magnesium hydroxide or another laxative, you should call your doctor. The effects of a laxatives can vary depending on the individual. The safest type of laxative to take is not magnesium hydroxide, but bulk-forming laxatives, also known as fiber laxatives or fiber supplements.
Cautions
It is possible to take an overdose of magnesium hydroxide; according to MedlinePlus, overdoses in children are usually accidental, but dieters may take a large amount of this laxative, believing it will help them lose weight. Overdose of a magnesium-based laxative can cause painful, watery bowel movements, stomach pain, vomiting, weakness, low blood pressure, slow rate of respiration, collapse, coma and even death. Contact National Poison Control at (800) 222-1222 immediately if you suspect an overdose.
References
- MayoClinic.com; Over-the-counter Laxatives for Constipation: Use with Caution; April 2011
- MedlinePlus Drug Information; Magnesium Hydroxide; September 2008
- Pubmed Health; Magnesium Hydroxide; September 2008
- MedlinePlus Medical Encyclopedia; Laxative Overdose; October 2009
- Drugs.com; Magnesium Hydroxide; December 2010
- MayoClinic.com; Laxatives (Oral Route); May 2011
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