Mysimba® – Possible Side Effects

Slim Clinic Patient Information

Mysimba® is an effective prescription medication for weight management. Like all medicines, it can cause side effects, although not everyone will experience them. Understanding potential reactions helps ensure safe and well-supervised treatment.

⚠️ Serious Side Effects

Contact your Slim Clinic doctor—or seek urgent medical attention—if you notice any serious or worrying symptoms.

Suicidal Thoughts or Depression

Frequency: Unknown

There have been reports of depression, suicidal thoughts, and suicide attempts in people using Mysimba.
Seek help immediately if you experience:

  • Thoughts of harming yourself

  • Worsening mood or new emotional symptoms

  • Persistent sadness, anxiety, or unusual behavioural changes

Seizures (Epileptic Fits)

Rare (up to 1 in 1,000 people)

Symptoms may include:

  • Convulsions

  • Loss of consciousness

  • Confusion afterward

Risk is higher if you exceed your dose or take interacting medications.

Severe Skin Reactions

Frequency: Unknown
Includes:

  • Erythema multiforme (red, itchy skin patches)

  • Stevens–Johnson syndrome (severe blistering of lips, eyes, mouth, nose, or genitals)

These conditions require immediate medical attention.

Rhabdomyolysis

Frequency: Unknown
Abnormal muscle breakdown that can damage the kidneys.
Warning signs:

  • Severe muscle pain or cramps

  • Muscle weakness

  • Dark urine

Lupus Flare or New Lupus-like Rash

If you have lupus, symptoms may worsen. Stop the medication and contact your doctor immediately if rashes or lesions occur, especially on sun-exposed skin.

Serotonin Syndrome

May occur when Mysimba is taken with antidepressants.
Symptoms may include:

  • Agitation, confusion, hallucinations

  • High temperature

  • Rapid heart rate or fluctuating blood pressure

  • Muscle stiffness, tremor, loss of coordination

  • Nausea, vomiting, diarrhoea

Seek urgent medical care.

Other Side Effects

Very Common (more than 1 in 10 people)

  • Nausea

  • Vomiting

  • Constipation

  • Headache

Common (up to 1 in 10 people)

  • Anxiety

  • Dizziness, vertigo

  • Tremor (“shaky” feeling)

  • Sleep disturbances (avoid taking Mysimba late in the day)

  • Altered taste

  • Dry mouth

  • Difficulty concentrating

  • Fatigue, drowsiness, low energy

  • Tinnitus (ringing in the ears)

  • Fast or irregular heartbeat

  • Hot flushes

  • High blood pressure (sometimes severe)

  • Upper abdominal pain or stomach pain

  • Excessive sweating

  • Rash or itching

  • Hair loss

  • Irritability, feeling “mentally unsettled”

Occasional (up to 1 in 100 people)

  • Hives

  • Hypersensitivity reactions

  • Unusual dreams

  • Nervousness

  • Tension or agitation

  • Mood swings

  • Intention tremor

  • Balance problems

  • Memory loss

  • Tingling or numbness in hands/feet

  • Motion sickness

  • Belching

  • Digestive upset, abdominal discomfort

  • Gallbladder inflammation (cholecystitis)

  • Elevated creatinine (kidney function marker)

  • Elevated liver enzymes or bilirubin

  • Liver conditions

  • Erectile difficulties

  • Feeling unwell or weak

  • Thirst

  • Heat sensations

  • Chest pain

  • Increased appetite or weight gain

  • Vaginal dryness

  • Irregular menstrual bleeding

  • Urinary urgency

Rare (up to 1 in 1,000 people)

  • Low lymphocyte count

  • Reduced red blood cell volume (low haematocrit)

  • Angioedema (swelling of eyelids, face, lips, tongue or throat)

  • Severe dehydration

  • Hallucinations

  • Fainting or near-fainting

  • Seizures

  • Stool containing fresh blood

  • Hernia

  • Toothache or tooth decay

  • Lower abdominal pain

  • Drug-related liver damage

  • Jaw pain

  • Vaginal bleeding

  • Feeling cold in hands/feet

Not Known (cannot be estimated)

  • Swollen lymph nodes

  • Mood swings, delusions, psychosis

  • Aggression, hostility, paranoia

  • Loss of sexual desire

  • Nightmares

  • Confusion or disorientation

  • Attention difficulties

  • Muscle stiffness, coordination issues

  • Eye irritation, blurred vision, photophobia

  • Ear pain

  • Breathing difficulties

  • Nasal congestion, sinus issues

  • Sore throat, voice changes, cough

  • Haemorrhoids or ulcers

  • Diarrhoea, gas

  • Hepatitis

  • Acne

  • Joint or muscle pain

  • Painful urination or frequent urination

  • Chills

  • Increased energy

When to Seek Medical Advice

Contact your Slim Clinic clinician if:
✔ Side effects are persistent, severe, or distressing
✔ You experience mood changes or emotional symptoms
✔ You develop skin reactions
✔ You have signs of dehydration
✔ You feel unsure whether a symptom is normal

Seek emergency care for severe allergic reactions, seizures, signs of serotonin syndrome, or severe abdominal pain.