May 31, 2016
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Side Effects


Clinical Trials

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in patients.

Commonly Observed (based on first year and second year data)

Gastrointestinal (GI) symptoms were the most commonly observed treatment-emergent adverse events associated with the use of XENICAL in the seven double-blind, placebo-controlled clinical trials and are primarily a manifestation of the mechanism of action. (Commonly observed is defined as an incidence of ≥ 5% and an incidence in the XENICAL 120 mg group that is at least twice that of placebo.)

Table 4 : Commonly Observed Adverse Events

Adverse Event Year 1 Year 2
XENICAL* % Patients
Placebo* % Patients
XENICAL* % Patients
Placebo* % Patients
Oily Spotting† 26.6 1.3 4.4 0.2
Flatus with Discharge 23.9 1.4 2.1 0.2
Fecal Urgency 22.1 6.7 2.8 1.7
Fatty/Oily Stool† 20.0 2.9 5.5 0.6
Oily Evacuation† 11.9 0.8 2.3 0.2
Increased Defecation 10.8 4.1 2.6 0.8
Fecal Incontinence 7.7 0.9 1.8 0.2
*Treatment designates XENICAL three times a day plus diet or placebo plus diet
†Oily discharge may be clear or have a coloration such as orange or brown.

In general, the first occurrence of these events was within 3 months of starting therapy. Overall, approximately 50% of all episodes of GI adverse events associated with XENICAL treatment lasted for less than 1 week, and a majority lasted for no more than 4 weeks. However, GI adverse events may occur in some individuals over a period of 6 months or longer.

Discontinuation of Treatment

In controlled clinical trials, 8.8% of patients treated with XENICAL discontinued treatment due to adverse events, compared with 5.0% of placebo-treated patients. For XENICAL, the most common adverse events resulting in discontinuation of treatment were gastrointestinal.

Other Adverse Clinical Events

The following table lists other treatment-emergent adverse events from seven multicenter, double-blind, placebo-controlled clinical trials that occurred at a frequency of ≥ 2% among patients treated with XENICAL 120 mg three times a day and with an incidence that was greater than placebo during year 1 and year 2, regardless of relationship to study medication.

Table 5 : Other Treatment-Emergent Adverse Events From Seven Placebo-Controlled Clinical Trials

Body System/Adverse Event Year 1 Year 2
XENICAL* % Patients
Placebo* % Patients
XENICAL* % Patients
Placebo* % Patients
Gastrointestinal System
  Abdominal Pain/Discomfort 25.5 21.4 - -
  Nausea 8.1 7.3 3.6 2.7
  Infectious Diarrhea 5.3 4.4 - -
  Rectal Pain/Discomfort 5.2 4.0 3.3 1.9
  Tooth Disorder 4.3 3.1 2.9 2.3
  Gingival Disorder 4.1 2.9 2.0 1.5
  Vomiting 3.8 3.5 - -
Respiratory System
  Influenza 39.7 36.2 - -
  Upper Respiratory Infection 38.1 32.8 26.1 25.8
  Lower Respiratory Infection 7.8 6.6 - -
  Ear, Nose & Throat Symptoms 2.0 1.6 - -
Musculoskeletal System
  Back Pain 13.9 12.1 - -
  Pain Lower Extremities - - 10.8 10.3
  Arthritis 5.4 4.8 - -
  Myalgia 4.2 3.3 - -
  Joint Disorder 2.3 2.2 - -
  Tendonitis - - 2.0 1.9
Central Nervous System
  Headache 30.6 27.6 - -
  Dizziness 5.2 5.0 - -
Body as a Whole
  Fatigue 7.2 6.4 3.1 1.7
  Sleep Disorder 3.9 3.3 - -
Skin & Appendages
  Rash 4.3 4.0 - -
  Dry Skin 2.1 1.4 - -
Reproductive, Female
  Menstrual Irregularity 9.8 7.5 - -
  Vaginitis 3.8 3.6 2.6 1.9
Urinary System
  Urinary Tract Infection 7.5 7.3 5.9 4.8
Psychiatric Disorder
  Psychiatric Anxiety 4.7 2.9 2.8 2.1
  Depression - - 3.4 2.5
Hearing & Vestibular Disorders
  Otitis 4.3 3.4 2.9 2.5
Cardiovascular Disorders
  Pedal Edema - - 2.8 1.9
*Treatment designates XENICAL 120 mg three times a day plus diet or placebo plus diet
– None reported at a frequency ≥ 2% and greater than placebo

In the 4-year XENDOS study, the general pattern of adverse events was similar to that reported for the 1-and 2-year studies with the total incidence of gastrointestinal-related adverse events occurring in year 1 decreasing each year over the 4-year period.

In clinical trials in obese diabetic patients, hypoglycemia and abdominal distension were also observed.

Pediatric Patients

In clinical trials with XENICAL in adolescent patients ages 12 to 16 years, the profile of adverse reactions was generally similar to that observed in adults.

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of XENICAL. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to XENICAL exposure.

  • Rare cases of increase in transaminases and in alkaline phosphatase and hepatitis that may be serious have been reported. There have been reports of hepatic failure observed with the use of XENICAL in postmarketing surveillance, with some of these cases resulting in liver transplant or death [see WARNINGS AND PRECAUTIONS].
  • Cases of reduced concentrations of cyclosporine have been reported when cyclosporine was co-administered with XENICAL [see WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS].
  • Rare cases of hypersensitivity have been reported with the use of XENICAL. Signs and symptoms have included pruritus, rash, urticaria, angioedema, bronchospasm and anaphylaxis. Very rare cases of bullous eruption have been reported.
  • Rare cases of leukocytoclastic vasculitis have been reported. Clinical signs include palpable purpura, maculopapular lesions, or bullous eruption.
  • Reports of decreased prothrombin, increased INR and unbalanced anticoagulant treatment resulting in change of hemostatic parameters have been reported in patients treated concomitantly with XENICAL and anticoagulants [see DRUG INTERACTIONS].
  • Hypothyroidism has been reported in patients treated concomitantly with XENICAL and levothyroxine [see DRUG INTERACTIONS].
  • Acute oxalate nephropathy after treatment with XENICAL has been reported in patients with or at risk for renal disease [see WARNINGS AND PRECAUTIONS].
  • Pancreatitis has been reported with the use of XENICAL in postmarketing surveillance. No causal relationship or physiopathological mechanism between pancreatitis and obesity therapy has been definitively established.
  • Lower gastrointestinal bleeding has been reported in patients treated with XENICAL. Most reports are nonserious; severe or persistent cases should be investigated further.
  • Convulsions have been reported in patients treated concomitantly with orlistat and antiepileptic drugs [see DRUG INTERACTIONS].

Read the Xenical (orlistat 120 mg) Side Effects Center for a complete guide to possible side effects



Data from a XENICAL and cyclosporine drug interaction study indicate a reduction in cyclosporine plasma levels when XENICAL was coadministered with cyclosporine. XENICAL and cyclosporine should not be simultaneously coadministered. Cyclosporine should be administered 3 hours after the administration of XENICAL [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS, and ADVERSE REACTIONS].

Fat-soluble Vitamin Supplements And Analogues

Data from a pharmacokinetic interaction study showed that the absorption of beta-carotene supplement is reduced when concomitantly administered with XENICAL. XENICAL inhibited absorption of a vitamin E acetate supplement. The effect of XENICAL on the absorption of supplemental vitamin D, vitamin A, and nutritionally-derived vitamin K is not known at this time [see CLINICAL PHARMACOLOGY].


Hypothyroidism has been reported in patients treated concomitantly with XENICAL and levothyroxine postmarketing [see ADVERSE REACTIONS]. Patients treated concomitantly with XENICAL and levothyroxine should be monitored for changes in thyroid function. Administer levothyroxine and XENICAL at least 4 hours apart [see DOSAGE AND ADMINISTRATION].


Vitamin K absorption may be decreased with XENICAL. Patients on chronic stable doses of warfarin who are prescribed XENICAL should be monitored closely for changes in coagulation parameters [see CLINICAL PHARMACOLOGY].


A pharmacokinetic study, where amiodarone was orally administered during orlistat treatment, demonstrated a reduction in exposure to amiodarone and its metabolite, desethylamiodarone [see CLINICAL PHARMOCOLOGY]. A reduced therapeutic effect of amiodarone is possible. The effect of commencing orlistat treatment in patients on stable amiodarone therapy has not been studied.

Antiepileptic Drugs

Convulsions have been reported in patients treated concomitantly with orlistat and antiepileptic drugs. Patients should be monitored for possible changes in the frequency and/or severity of convulsions [see ADVERSE REACTIONS].

Drug Abuse And Dependence


As with any weight-loss agent, the potential exists for abuse of XENICAL in inappropriate patient populations (eg, patients with anorexia nervosa or bulimia). See INDICATIONS AND USAGE for recommended prescribing guidelines.

Read the Xenical Drug Interactions Center for a complete guide to possible interactions

Pharmacist reviewed on 8/26/2015

Prescribing Document Revised: October 2013

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 8/26/2015

Side Effects

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