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Sympazan Side Effects

Generic name: clobazam

Medically reviewed by Last updated on Nov 15, 2020.

Note: This document contains side effect information about clobazam. Some of the dosage forms listed on this page may not apply to the brand name Sympazan.

For the Consumer

Applies to clobazam: oral film, oral suspension, oral tablet


Oral route (Suspension; Tablet)

Concomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, or death. Reserve use for patients for whom alternative therapies are inadequate and limit use to lowest possible dose and shortest possible duration. Monitor for signs or symptoms of respiratory depression and sedation.

Side effects requiring immediate medical attention

Along with its needed effects, clobazam (the active ingredient contained in Sympazan) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking clobazam:

More common

  • Difficulty with swallowing
  • fever
  • shakiness and unsteady walk
  • unsteadiness, trembling, or other problems with muscle control or coordination

Less common

  • Change in speech pattern
  • restlessness
  • slurred speech
  • trouble sitting still
  • trouble speaking

Incidence not known

  • Agitation
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • blood in the urine or stools
  • chest pain
  • chills
  • confusion as to time, place, or person
  • cough
  • diarrhea
  • difficult or troubled breathing
  • holding false beliefs that cannot be changed by fact
  • irregular, fast or slow, or shallow breathing
  • itching
  • joint or muscle pain
  • lack of feeling or emotion
  • painful or difficult urination
  • pale or blue lips, fingernails, or skin
  • pinpoint red spots on the skin
  • rash, hives, or welts
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • seeing, hearing, or feeling things that are not there
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips
  • swollen glands
  • troubled breathing with exertion
  • unusual bleeding or bruising
  • unusual excitement, nervousness, or restlessness
  • unusual tiredness or weakness

Side effects not requiring immediate medical attention

Some side effects of clobazam may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Aggressive
  • body aches or pain
  • decreased appetite
  • difficulty having a bowel movement
  • drooling
  • ear congestion
  • irritability
  • loss of voice
  • nasal congestion
  • runny nose
  • sleepiness or unusual drowsiness
  • sneezing
  • vomiting

Less common

  • Bladder pain
  • cloudy urine
  • cough with mucus
  • frequent urge to urinate
  • increased appetite
  • lower back or side pain

Incidence not known

  • Double vision
  • full or bloated feeling
  • headache
  • muscle spasms
  • pressure in the stomach
  • red skin
  • swelling of the stomach area

For Healthcare Professionals

Applies to clobazam: oral film, oral suspension, oral tablet


The most commonly reported side effects were somnolence or sedation, tiredness, pyrexia, and lethargy.[Ref]

Nervous system

Very common (10% or more): Somnolence or sedation (up to 32%), drowsiness (up to 32%), somnolence (up to 25%), lethargy (up to 15%), drooling (up to 14%), ataxia (up to 10%)

Common (1% to 10%): Dizziness, dysarthria, headache, psychomotor hyperactivity, sedation, slurred speech, tremor

Frequency not reported: Amnesia, anterograde amnesia, disorders of articulation, disturbance in attention, fine finger tremor, hangover, impairment in consciousness, memory impairment, nystagmus, potentiation of sedation from concomitant use with central nervous system depressants, sleepiness, slowed/indistinct speech, slowing of reaction time, speech disorder, unsteadiness of gait and other motor functions, unsteady movement[Ref]


Very common (10% or more): Tiredness (up to 32%), pyrexia (up to 17%)

Common (1% to 10%): Fatigue

Frequency not reported: Drug tolerance, fall, hypothermia, risks from concomitant use with opioids, paradoxical reactions[Ref]


Very common (10% or more): Aggression/aggressiveness (up to 14%), irritability (up to 11%)

Common (1% to 10%): Confusion, depression, insomnia

Frequency not reported: Acute agitational states, agitation, anxiety, benzodiazepine abuse, decreased libido, delusion, difficulty falling asleep/sleeping through, euphoria, fits of rage, habituation, hallucinations, inappropriate behavior, loss of libido, nightmares, numbed emotions, physical and psychological dependence, psychotic reactions, restlessness, suicidal behavior and ideations, suicidal tendencies, unmasking of preexisting depression, withdrawal symptoms/rebound phenomena

Postmarketing reports: Apathy, confusional state, delirium[Ref]


Very common (10% or more): Upper respiratory tract infection (up to 14%)

Common (1% to 10%): Bronchitis, cough, pneumonia

Frequency not reported: Deterioration of respiratory insufficiency, respiratory depression, respiratory disorders, respiratory insufficiency

Postmarketing reports: Aspiration[Ref]


Very common (10% or more): Constipation (up to 10%)

Common (1% to 10%): Diarrhea, dry mouth, dysphagia, nausea, vomiting

Postmarketing reports: Abdominal distention[Ref]


Common (1% to 10%): Decreased appetite, increased appetite

Frequency not reported: Anorexia, appetite loss, weight gain[Ref]


Common (1% to 10%): Rash

Frequency not reported: Cutaneous reaction, photosensitivity reactions, pruritus, serious dermatological reactions, Stevens-Johnson syndrome (SJS)/fatal SJS, sweating, toxic epidermal necrolysis (TEN)/fatal TEN, urticaria

Postmarketing reports: Facial and lip edema[Ref]


Common (1% to 10%): Urinary tract infection

Postmarketing reports: Urinary retention[Ref]


Common (1% to 10%): Hypotension[Ref]


Frequency not reported: Muscle aches, muscle spasm/frequent muscle spasms, muscle stiffness, muscle weakness[Ref]


Frequency not reported: Blurred vision, diplopia/double vision, visual disorders[Ref]


Frequency not reported: Abnormal hematologic laboratory tests

Postmarketing reports: Anemia, eosinophilia, leukopenia, thrombocytopenia[Ref]


Frequency not reported: Abnormal liver function tests

Postmarketing reports: Increased hepatic enzymes[Ref]


Postmarketing reports: Angioedema[Ref]


1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

2. "Product Information. Onfi (clobazam)." Lundbeck Inc, Deerfield, IL.

3. "Product Information. Frisium (clobazam)." Sanofi-Aventis, Laval, IN.

4. Cerner Multum, Inc. "Australian Product Information." O 0

Frequently asked questions

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.