Medically reviewed on Sep 17, 2018
What is Fiber Lax?
Fiber Lax is a bulk-forming laxative that increases the amount of water in your stools to help make them softer and easier to pass.
Fiber Lax is used to treat constipation and to help maintain regular bowel movements.
Fiber Lax may also be used for purposes not listed in this medication guide.
Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.
Before taking this medicine
Ask a doctor or pharmacist if it is safe for you to use this medicine if you have other medical conditions, especially:
a blockage in your intestines;
a history of bleeding from your rectum;
a sudden change in bowel habits that lasts 2 weeks or longer; or
if you have been constipated for more than 1 week.
Ask your doctor before taking Fiber Lax if you are pregnant or breast-feeding.
This medicine may contain phenylalanine. Talk to your doctor before taking Fiber Lax if you have phenylketonuria (PKU).
Do not give this medicine to a young child without the advice of a doctor.
How should I take Fiber Lax?
Fiber Lax is usually taken 1 to 4 times per day. Use exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Overuse of a laxative may cause damage to the nerves, muscles, or tissues in your intestines.
Take this medicine with a full glass (8 ounces) of water or other liquid. Then drink one more glass of water.
The chewable tablet form of polycarbophil must be chewed before you swallow it. After chewing and swallowing the tablet, drink a full glass of water.
Taking Fiber Lax without enough liquid may cause the tablet to swell in your throat and cause choking, especially in older adults.
Seek emergency medical attention if you have chest pain, vomiting, trouble swallowing, or trouble breathing after taking this medicine.
Drink plenty of fluids each day while you are taking Fiber Lax.
You should have a bowel movement within 12 hours to 3 days.
Call your doctor if your symptoms do not improve after 3 days of treatment.
Store at room temperature away from moisture and heat.
What happens if I miss a dose?
Since Fiber Lax is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
What should I avoid while taking Fiber Lax?
Avoid taking Fiber Lax within 2 hours before or 2 hours after you take any other medicines. A laxative can make it harder for your body to absorb other medicines.
Fiber Lax side effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
severe stomach cramps, rectal bleeding; or
no bowel movement within 3 days after using Fiber Lax.
Common side effects may include:
mild stomach pain;
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What other drugs will affect Fiber Lax?
Other drugs may interact with polycarbophil, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
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