Lorcaserin is used to help adults who are obese or who are overweight and have weight-related medical problems to lose weight and keep from gaining back that weight. Lorcaserin must be used along with a reduced calorie diet and an exercise plan. Lorcaserin is in a class of medications called serotonin receptor agonists. It works by increasing feelings of fullness so that less food is eaten.

Side Effects Of Lorcaserin

Lorcaserin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • constipation
  • dry mouth
  • excessive tiredness
  • pain in the back or muscles
  • headache
  • dizziness
  • difficulty falling asleep or staying asleep
  • anxiety
  • difficult, painful, or frequent urination
  • cough
  • toothache
  • blurred vision or other vision changes
  • dry eyes

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:

  • agitation
  • confusion
  • hallucinations (seeing things or hearing voices that are not there)
  • difficulty with coordination
  • muscle spasms, stiffness, or twitching
  • restlessness
  • fast, slow, or irregular heartbeat
  • sweating
  • fever
  • nausea
  • vomiting
  • diarrhea
  • difficulty breathing
  • swelling of the hands, arms, feet, or legs
  • difficulty paying attention or remembering information
  • depression
  • thinking about harming or killing yourself or planning or trying to do so
  • feeling high or unusually happy
  • feeling as though you are outside of your body
  • an erection that lasts longer than 4 hours
  • discharge from the breast
  • breast enlargement in males

Lorcaserin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

Warnings & Precautions

Before taking lorcaserin:

  • tell your doctor and pharmacist if you are allergic to lorcaserin, any other medications, or any of the ingredients in lorcaserin tablets or extended-release tablets. Ask your pharmacist or check the patient information for a list of the ingredients.
  • tell your doctor and pharmacist what prescription and nonprescription medications and vitamins you are taking or plan to take. Be sure to mention any of the following: bupropion (Aplenzin, Forfivo, Wellbutrin, Zyban); cabergoline; codeine (in some pain medications and cough medications); dextromethorphan (in cough and cold medications); flecainide (Tambocor); insulin and other medications for diabetes; linezolid (Zyvox); lithium (Lithobid); medications for erectile dysfunction, or mental illness; medications for migraine headaches such as almotriptan (Axert), eletriptan (Relpax), frovatriptan (Frova), naratriptan (Amerge), rizatriptan (Maxalt), sumatriptan (Imitrex), and zolmitriptan (Zomig); other medications for weight loss; metoprolol (Toprol); mexiletine; monoamine oxidase (MAO) inhibitors including isocarboxazid (Marplan), linezolid (Zyvox), methylene blue, phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar), and tranylcypromine (Parnate); ondansetron (Zofran); propafenone (Rythmol); selective serotonin reuptake inhibitors (SSRIs) such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem, in Symbyax), fluvoxamine, paroxetine (Paxil), and sertraline (Zoloft); selective serotonin/norepinephrine reuptake inhibitors (SNRIs) such as duloxetine (Cymbalta) and venlafaxine (Effexor); tamoxifen (Soltamox); timolol (Blocadren); tricyclic antidepressants (TCAs) such as amitriptyline, amoxapine, clomipramine (Anafranil), desipramine (Norpramin), doxepin (Silenor), imipramine (Tofranil), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), and trimipramine (Surmontil); and tramadol (Conzip, Ultram, Ryzolt). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with lorcaserin, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
  • tell your doctor what herbal products and nutritional supplements you are taking, especially St. John’s wort, tryptophan, and herbs or supplements for weight loss.
  • tell your doctor if you are pregnant or plan to become pregnant. Your doctor will probably tell you not to take lorcaserin. If you become pregnant while taking lorcaserin, call your doctor immediately. Lorcaserin may harm your unborn baby.
  • tell your doctor if you have or have ever had blood cell problems such as sickle cell anemia (a disease of the red blood cells), multiple myeloma (cancer of the plasma cells), or leukemia (cancer of the white blood cells); a condition that affects the shape of the penis such as angulation, cavernosal fibrosis, or Peyronie’s disease; diabetes; heart failure, slow or irregular heartbeat, or other heart problems; or liver or kidney disease.
  • do not breastfeed while taking lorcaserin.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking lorcaserin.
  • you should know that lorcaserin may cause drowsiness and difficulty paying attention or remembering information. Do not drive a car or operate machinery until you know how this medication affects you.

Lorcaserin Dosage

Lorcaserin comes as a tablet and as an extended-release (long-acting) tablet to take by mouth. The tablets are usually taken with or without food twice a day. The extended-release tablets are usually taken with or without food once a day. Take lorcaserin at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take lorcaserin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Swallow the extended-release tablets whole; do not split, chew, or crush them.

Lorcaserin may be habit-forming. Do not take a larger dose, take it more often, or take it for a longer period of time than prescribed by your doctor.

If you do not lose a certain amount of weight during the first 12 weeks of your treatment, it is not likely that you will benefit from taking lorcaserin. Your doctor may tell you to stop taking lorcaserin if you do not lose enough weight during the first 12 weeks of your treatment.

Lorcaserin will help control your weight only if you continue to take it. Do not stop taking lorcaserin without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.


Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your body’s response to lorcaserin.

Do not let anyone else take your medication. Lorcaserin is a controlled substance. Prescriptions may be refilled only a limited number of times; ask your pharmacist if you have any questions.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.