Orlistat Side Effects (And How to Manage Them)

Orlistat, sold under the brand name Xenical or as a generic medication, is an oral weight loss aid that helps prevent the absorption of dietary fats. It’s designed to be used alongside a low-calorie, low-fat diet and regular exercise. While Orlistat can be effective for weight loss, it’s important to be aware of its potential side effects, interactions, and how to manage them.

The most frequently reported side effects are related to the digestive system. These include oily or fatty stools, flatulence with discharge, frequent or urgent bowel movements, and abdominal discomfort.
These gastrointestinal side effects are usually mild and can be managed by sticking to a low-fat diet.

Some users may experience headaches. Staying well-hydrated, using over-the-counter pain relievers like paracetamol or ibuprofen, and ensuring adequate rest can help manage this side effect in the short term.
There are instances of mild upper respiratory infections like colds. Rest, fluids, and over-the-counter medications like decongestants can help manage symptoms.

Rarely, some people experience an allergic reaction to Orlistat. Symptoms can include itching, rash, difficulty breathing, and swelling of the face, lips, or tongue.
Seek medical attention immediately if you experience these symptoms. Treatment typically involves antihistamines and corticosteroids, but severe cases may require emergency intervention.

In very rare cases, severe liver injury has been reported. Symptoms to watch for include jaundice (yellowing of the skin or eyes), dark urine, loss of appetite, and severe upper stomach pain.
If you notice these symptoms, stop taking Orlistat and seek medical attention immediately.
There have been rare reports of kidney stones, which can cause severe back or flank pain, blood in urine, and painful urination.
Staying well-hydrated and taking painkillers can help manage mild cases, but a medical review should always be sought as severe cases may require medical intervention such as lithotripsy or surgery.

The most common long-term side effects of Orlistat are gastrointestinal in nature. These include frequent and urgent bowel movements, oily or fatty stools, flatulence, and abdominal discomfort. These effects are a direct result of unabsorbed fat passing through the digestive system. While these side effects are often mild and manageable with dietary adjustments, they can be persistent and uncomfortable for some users.

Long-term use of Orlistat can impair the absorption of fat-soluble vitamins (A, D, E, and K) and other essential nutrients. This can lead to deficiencies over time if not properly managed. To mitigate this risk, individuals taking Orlistat are often advised to take a multivitamin supplement at least two hours before or after taking the medication. 

There have been reports linking long-term use of Orlistat to rare but serious liver injury and kidney stones. The mechanism is not entirely understood, but it is thought that Orlistat’s interference with fat absorption could lead to an accumulation of unabsorbed fats and fat-soluble substances, potentially causing damage to these organs. Regular monitoring of liver and kidney function is recommended for individuals who take Orlistat.

To balance the risk of side effects and the benefits of weight loss, treatment with Orlistat must be discussed with a doctor after taking it for 3 months.

Orlistat can interact with other medications, which might affect how well they work or increase the risk of side effects.

• Cyclosporine. Taking Orlistat with cyclosporine can reduce the effectiveness of cyclosporine. It’s recommended to take cyclosporine at least three hours before or after Orlistat. Increased monitoring of cyclosporine levels may be necessary.
• Levothyroxine. Orlistat can interfere with the absorption of levothyroxine, a thyroid hormone replacement. Separate the dosing times by at least four hours. Increased thyroid function tests can help ensure proper dosing.
• Blood thinners. Orlistat can affect the absorption of vitamin K, which is important for blood clotting. If you’re on blood thinners like warfarin, your doctor may need to monitor your blood more closely and adjust the dosage as necessary.
• Diabetes medications. Orlistat can impact blood sugar control, so if you’re taking medications for diabetes, you might need adjustments to your doses. Regular blood sugar monitoring can help identify this interaction.
• Oral contraceptives. Orlistat may reduce the effectiveness of oral contraceptives, leading to unwanted pregnancies. If you are taking the contraceptive pill, discuss this with your doctor before starting Orlistat
• Anti-epileptics. There may be an increased risk of seizures if Orlistat reduces the absorption of medication for epilepsy, so it is important to discuss all your medication with a doctor before taking Orlistat.
• HIV treatment and prevention tablets. Antiretrovirals might not be absorbed as well if taking Orlistat, so discuss this with a doctor to ensure that your protection against, or treatment for, HIV is not affected.

Certain foods and supplements can also interact with Orlistat.

• High-fat meals. Consuming high-fat meals while taking Orlistat can increase gastrointestinal side effects. Stick to a diet where no more than 30% of the calories come from fat. Keeping a food diary can help track fat intake.
• Vitamins. Orlistat can reduce the absorption of fat-soluble vitamins (A, D, E, and K). Taking a multivitamin supplement at least two hours before or after Orlistat can help maintain adequate vitamin levels. Eating a diet rich in these vitamins can help support your health.

Certain medical conditions might affect how well Orlistat works or increase the risk of side effects.

• Chronic malabsorption syndrome. People with this condition should not use Orlistat as it can worsen the condition.
• Gallbladder problems. If you have a history of gallbladder issues, such as cholestasis, Orlistat may not be suitable for you. Alternative weight loss treatments should be considered.
• Kidney problems. Orlistat can increase the risk of kidney stones, so those with kidney issues should use it cautiously. Regular kidney function tests can help monitor for potential issues.
• Pregnancy and breastfeeding. Discuss Orlistat with your doctor if you might be, or are trying to get, pregnant, or are breastfeeding.

Dietary guidelines. Follow a low-fat diet to minimise gastrointestinal side effects. Distribute your daily fat intake evenly across your meals.

Regular monitoring. Regular check-ups with your doctor can help monitor your progress and adjust your treatment as needed. Blood tests and other assessments can track your health and response to the medication.

Hydration. Stay well-hydrated to reduce the risk of kidney stones. Aim for at least 8 glasses of water a day.

Taking more than the recommended dose of Orlistat does not increase its effectiveness and can lead to severe gastrointestinal side effects. If you suspect an overdose, seek medical attention immediately. Symptoms of overdose might include severe stomach pain, nausea, vomiting, and diarrhoea.

This article is for general information only and should not be used for the diagnosis or treatment of medical conditions. Medic Spot Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. In the event of an emergency, please call 999 for immediate assistance.

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