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Constipation is a common condition that makes it difficult to have a bowel movement. It can be caused by:

• Your diet
• Certain medicines
• Dehydration
• Too little physical activity
• Intestinal problems

Constipation can usually be treated with medicines called laxatives. Many laxatives are available over-the-counter (OTC). This means you can buy them at the store without a prescription. Some constipation medicines may be called stool softeners or fibre supplements.

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How do laxatives work?

There are several different kinds of laxatives. Each one works a different way. These are the most common types.

Bulk-forming laxatives

These laxatives add “soluble” fibre to the stool. This causes the stool to absorb more water.  It creates larger, softer stools. The larger stools help trigger the bowel (intestines) to contract. This moves the stools out. Bulk-forming laxatives generally are the safest type of laxative.

Examples of bulk-forming laxatives include:

• Psyllium (1 brand name: Metamucil)
• Polycarbophil (1 brand name: Mitrolan)
• Methylcellulose

To reduce your risk of side effects, you should start slowly and make sure to drink plenty of fluids while taking bulk-forming laxatives. Gradually increase how much you use until you get the results you want.

Lubricant laxatives

These coat the surface of the stools to make them slippery. Doing this helps the stools move out of the body more easily. Glycerin suppositories lubricate the inside of the anus (the outside opening to the intestine) to make it easier to pass hard stools out of the body.

Stool softeners

These help mix fluid into stools to soften them. This makes stools easier to pass out of the body. An example of a stool softener is docusate (1 brand name: Colace).

Osmotic laxatives

These cause the intestine to hold more fluid. This softens stools and helps the bowel move them out. Examples include polyethylene glycol (1 brand name: Restoralax) and magnesium hydroxide solution (called milk of magnesia).

Stimulant laxatives

These are the harshest type of laxatives. They cause the bowel to squeeze or contract to move the stools out. Stimulant laxatives should not be used for more than a few days. When these laxatives are taken for a long time, the bowel can lose its muscle tone and “forget” how to push the stool out on its own. Bisacodyl (1 brand name: Dulcolax) and sennosides (1 brand name: Senokot) are examples of stimulant laxatives.

Should I use a laxative to treat constipation?

Most of the time, constipation doesn’t require treatment with laxatives. It will usually go away on its own. Or you make changes in your diet and other habits. You can prevent or treat constipation by:

• Eating enough foods rich in soluble and insoluble fibre (such as bran, oats, foods made with whole grains, fruits, and vegetables)
• Drinking enough fluids
• Getting enough exercise

 You may try all of these things and still be constipated. That is when taking a laxative may help you.

How do I safely take OTC laxatives?

Before you take an OTC laxative, read the directions on the drug facts label. This will tell you how much medicine to take and how often to take it. If you have any questions about how much medicine to take, contact your healthcare provider or pharmacist. Keep a record of the OTC medicines you are using and when you take them. If you need to visit your healthcare provider, take this list with you.

Follow these tips to make sure you are taking the right amount of an OTC laxative:

• Take only the amount recommended on the medicine’s label. Don’t assume that more medicine will work better or quicker. Taking more than the recommended amount can be dangerous.
• If you are taking a prescription medicine, ask your healthcare provider or pharmacist if it’s okay to also take an OTC laxative.

How can I safely store OTC laxatives?

Store all medicines up and away, out of reach and sight of young children. Keeping medicines in a cool, dry place will help prevent them from becoming less effective before their expiration dates. Do not store medicines in bathrooms or bathroom cabinets, which are often hot and humid.

Things to consider

Most laxatives don’t have side effects if you use them correctly. However, sometimes they can cause cramping, gas, bloating, nausea, or diarrhea.

Laxatives aren’t meant for long-term use. Don’t use laxatives for longer than 1 week unless your healthcare provider recommends it. Long-term use or overuse of laxatives can cause health problems. Overusing laxatives may also hide symptoms your healthcare provider should know about. This could delay finding out about other health problems and starting treatment.

 Some people are at risk for electrolyte imbalances while taking certain laxatives. They include children and people who have diabetes or kidney disease. Electrolytes are substances in your body. They help your nerves, organs, and muscles work properly.

Taking laxatives can cause you to eliminate too many electrolytes. When this happens, you may have side effects. These could include nausea, vomiting, headache, confusion, fatigue, and muscle weakness or spasms. Electrolyte imbalance can be serious, so contact your child’s healthcare provider before giving your child a laxative. If you have a chronic condition, be sure to contact your healthcare provider before taking a laxative.

Who shouldn’t take laxatives?

Don’t take laxatives if you are allergic to any of the ingredients. Some people may be allergic to psyllium, a key ingredient in 1 type of bulk-forming laxative.

If you have a condition called phenylketonuria, you shouldn’t take a laxative that contains phenylalanine.

Could laxatives cause problems with any medicines or supplements I take?

Laxatives can get in the way of how your body absorbs certain medicines and some nutrients. Don’t take any other medicines within 2 hours of taking a laxative. If you’re taking a prescription medicine of any kind, contact your healthcare provider or pharmacist before taking a laxative. You also shouldn’t mix different types of laxatives. This includes oral laxatives (taken by mouth) and suppositories. Don’t take bisacodyl within 1 hour of taking antacids or drinking milk.

Mineral oil and castor oil are sometimes used as laxatives. They shouldn’t be used often. If mineral oil is used often, it can cause deficiencies of vitamins A, D, E, and K. Castor oil is a stimulant laxative. Using it a lot can cause you to lose muscle tone in your bowel. This can lead to long-term constipation. Mineral oil and castor oil also interact with some medicines.  These include blood‑thinning medicines, antibiotics such as tetracycline, and certain heart and bone medicines.

When should I contact my healthcare provider?

If you have any of the following symptoms, contact your healthcare provider before using an OTC laxative:

• Nausea
• Stomach pain
• Sudden change in your bowel habits that lasts 2 weeks or longer
• Vomiting
• Blood in stool
• Black or dark-coloured stool

Stop taking laxatives and contact your healthcare provider if you have any bleeding from your rectum or if you don’t have a bowel movement after using a laxative. These could be signs of a more serious problem.