Orlistat is a weight-loss medication available both over-the-counter as Alli and by prescription as Xenical. It is a lipase inhibitor that works in the gastrointestinal tract to block the action of specific enzymes. These enzymes, gastric and pancreatic lipases, are responsible for breaking down dietary fats into smaller molecules that can be absorbed by the body. By inhibiting these enzymes, orlistat prevents the digestion and absorption of a portion of the fat consumed in meals, which aids in weight management.
Common Gastrointestinal Side Effects
The most frequent side effects of orlistat are directly related to its mechanism of action and occur within the digestive system. Because the medication prevents about 30% of dietary fat from being broken down and absorbed, this undigested fat must pass through the intestines and be eliminated. This process leads to predictable gastrointestinal events.
Users often experience oily spotting on underwear or oily discharge. Another common effect is flatus with discharge, which is passing gas that is accompanied by an oily substance. Bowel habits may also change, with many people reporting an urgent need to have a bowel movement or an increase in the frequency of their movements. The stools themselves can appear visibly fatty or oily, a condition known as steatorrhea. Some individuals may also find it difficult to control their bowel movements.
Managing Digestive Side Effects
The gastrointestinal side effects of orlistat are manageable through dietary adjustments. Controlling the amount of fat in the diet can significantly reduce their severity. The likelihood of experiencing effects like oily stools or urgent bowel movements increases when orlistat is taken with a high-fat meal.
A primary strategy for management is adhering to a reduced-fat, balanced diet. It is often recommended that total fat intake should constitute no more than 30% of daily calories. For someone on a 2,000-calorie per day diet, this would equate to approximately 67 grams of fat. Distributing this fat intake evenly across the day’s main meals, rather than consuming it all in one sitting, can also help prevent an overload of unabsorbed fat in the digestive tract at any one time. Keeping a food diary to track fat consumption can be a useful tool in minimizing these digestive disturbances.
Impact on Nutrient Absorption
Beyond its effects on fat, orlistat’s mechanism can interfere with the body’s ability to absorb certain essential nutrients. Specifically, the medication can reduce the absorption of fat-soluble vitamins. The vitamins affected are A, D, E, and K, along with beta-carotene, a precursor to vitamin A.
This interference means that long-term use could potentially lead to lower levels of these important vitamins. To counteract this, it is recommended for individuals taking orlistat to take a daily multivitamin containing these vitamins. To ensure the multivitamin is effective, it should be taken at a different time from the orlistat dose. A common approach is to take the multivitamin at least two hours before or after an orlistat dose, or simply at bedtime, to allow for proper absorption.
Serious but Rare Complications
There are rare but serious complications associated with orlistat that require immediate medical attention. One of the most significant is the potential for severe liver injury. Warning signs of liver problems include:
- Jaundice, which is a yellowing of the skin or eyes
- Dark urine
- Loss of appetite
- Pain in the upper stomach
Kidney problems, though uncommon, can also occur, specifically the formation of kidney stones. This risk may be linked to changes in how the body processes certain substances, leading to an increase of oxalate in the urine. Symptoms that could indicate kidney issues include sharp back pain, blood in the urine, or painful urination.
Severe allergic reactions can happen, manifesting as:
- Hives
- Itching
- Rash
- Severe dizziness
- Difficulty breathing
If any of these symptoms appear, stop the medication and seek prompt medical care.