Colesevelam is a medication primarily used to manage cholesterol levels in the blood. It belongs to a class of drugs called bile acid sequestrants and is typically prescribed alongside diet and exercise to reduce elevated low-density lipoprotein (LDL) cholesterol. Beyond this primary use, Colesevelam, often known by the brand name Welchol, has a secondary application in medicine. The 625mg tablet formulation is frequently used to address a specific type of chronic diarrhea, offering relief to individuals with a challenging digestive condition. This dual function highlights the drug’s versatility in treating separate, yet interconnected, health issues.
Treating Diarrhea Caused by Bile Acid Malabsorption
The chronic diarrhea Colesevelam addresses is often the result of a condition known as Bile Acid Malabsorption (BAM). Bile acids are compounds the liver produces from cholesterol, which are then stored in the gallbladder and released into the small intestine to aid in the digestion and absorption of dietary fats. Normally, about 97% of these bile acids are reabsorbed in the lower part of the small intestine and recycled back to the liver.
In individuals with BAM, this recycling process is disrupted, causing an excess amount of bile acids to spill over into the large intestine, or colon. The presence of these unabsorbed bile acids in the colon is irritating to the lining of the bowel. They stimulate the colon to secrete water and electrolytes, which results in an increased volume of fluid within the large intestine. This leads directly to the characteristic symptom of BAM: chronic, watery diarrhea.
Colesevelam functions as a bile acid sequestrant by binding directly to these excess bile acids in the intestinal tract. The drug is a polymer that forms a complex with the bile acids, essentially sequestering or trapping them. Because Colesevelam itself is not absorbed into the bloodstream, the entire complex—the drug bound to the bile acids—is simply passed out of the body in the stool.
By binding and removing the bile acids before they can reach and irritate the colon, Colesevelam effectively prevents the secretory action that causes the diarrhea. This specific action makes the medication a targeted and effective treatment for chronic diarrhea related to BAM.
Practical Guidance for Taking the 625mg Tablets
The 625mg tablet is the standard formulation used for treating bile acid malabsorption, and it is important to follow specific instructions when beginning therapy. The dosage for diarrhea can vary significantly between patients, but many find an effective dose to be between two and six tablets daily. A common regimen involves a total daily dose of 3.75 grams, which equates to six 625mg tablets.
To maximize the drug’s effectiveness and minimize potential gastrointestinal discomfort, the tablets should be taken with meals and with a full glass of water. Taking the medication with food helps ensure it is present in the digestive tract when bile acids are released, improving the binding process. Splitting the total dose into two or three administrations throughout the day, such as three tablets taken twice daily with meals, is often recommended.
Some healthcare providers suggest starting with a lower dose and gradually increasing the number of tablets over a week or two. This slow titration allows the digestive system to adapt to the medication, potentially reducing initial side effects like bloating or gas. Consistency is important, and patients should aim to take the medication at the same times each day with their meals.
If a dose is missed, it should be taken as soon as it is remembered, unless it is already close to the time for the next scheduled dose. In that case, the missed dose should be skipped entirely, and the patient should resume the regular schedule. Patients must adhere strictly to the specific instructions provided by the prescribing physician, as the dosage for BAM may differ from the dosage used to lower cholesterol.
Managing Potential Adverse Effects
Colesevelam can lead to adverse effects, most of which are related to the digestive system due to its non-absorbed nature. The most commonly reported side effects include constipation, general upset stomach, gas, and abdominal bloating. These effects are a direct result of the drug’s action in the gut and tend to be mild, often improving as the body adjusts to the treatment.
Constipation, however, can occasionally become severe, and patients are advised to contact their doctor if they experience significant discomfort or a lack of a bowel movement for several days. In rare cases, more serious symptoms, such as severe abdominal pain with nausea or vomiting, could signal a bowel obstruction or pancreatitis, necessitating immediate medical attention. The medication is not recommended for use in patients who have a history of bowel obstruction or very high triglyceride levels, which are above 500 mg/dL.
A significant consideration when taking Colesevelam is its potential for drug interactions. Since the drug binds substances in the gut, it can interfere with the absorption of other orally taken medications. To minimize this risk, many drugs, including certain vitamins (A, D, E, and K), oral contraceptives, levothyroxine, and some diabetes medications like glyburide or glipizide, should be taken at least four hours before Colesevelam. This separation ensures that the other drug has sufficient time to be absorbed.