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Sympazan Side Effects

Generic name: clobazam

Medically reviewed by Philip Thornton, DipPharm. Last updated on Nov 19, 2023.

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

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


Oral route (Film; Suspension; Tablet)

Warning: Risks from Concomitant Use with Opioids; Abuse, Misuse, and Addiction: and Dependence and Withdrawal ReactionsConcomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of these drugs for patients for whom alternative treatment options are inadequate. Limit dosages and durations to the minimum required. Follow patients for signs and symptoms of respiratory depression and sedation.The use of benzodiazepines, including clobazam, exposes users to risks of abuse, misuse, and addiction, which can lead to overdose or death. Before prescribing clobazam and throughout treatment, assess each patient's risk for abuse, misuse, and addiction.The continued use of benzodiazepines, including clobazam, may lead to clinically significant physical dependence. The risks of dependence and withdrawal increase with longer treatment duration and higher daily dose. Abrupt discontinuation or rapid dosage reduction of clobazam after continued use may precipitate acute withdrawal reactions, which can be life-threatening. To reduce the risk of withdrawal reactions, use a gradual taper to discontinue clobazam or reduce the dosage.

Serious side effects of Sympazan

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

Less common

Incidence not known

Get emergency help immediately if any of the following symptoms of overdose occur while taking clobazam:

Symptoms of overdose

Other side effects of Sympazan

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

Less common

Incidence not known

For Healthcare Professionals

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


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

Nervous system

Altered consciousness more commonly occurred in older patients, and may have been combined with respiratory disorders.

Anterograde amnesia occurred in the normal dose range, but was more frequently reported with higher doses.

Articulation disorders, gait disorders, other motor function disorders, slow speech, and/or speech disorder were typically reversible and occurred more frequently with higher doses and/or at the beginning of treatment.

Fine tremor of the fingers typically occurred at the beginning of treatment, and usually disappeared with continued treatment.

Nystagmus occurred more frequently with higher doses and/or with prolonged treatment.

Somnolence occurred more frequently with higher doses and/or at the beginning of treatment.[Ref]

Very common (10% or more): Sedation or somnolence (up to 32%), somnolence (up to 25%), lethargy (up to 15%), drooling (up to 14%)

Common (1% to 10%): Ataxia, dizziness, disturbance in attention, dysarthria, headache, psychomotor hyperactivity, sedation, slow speech, slurred speech, speech disorder, tremor

Uncommon (0.1% to 1%): Amnesia, anterograde amnesia, memory impairment

Very rare (less than 0.01%): Impaired consciousness

Frequency not reported: Articulation disorders, cognitive disorder, fine tremor of the fingers, gait disorders, indistinct speech, nystagmus, other motor function disorders, slow response to stimuli, unsteady gait/movement[Ref]


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

Common (1% to 10%): Drug tolerance, fatigue

Uncommon (0.1% to 1%): Fall

Frequency not reported: Hangover, hypothermia, paradoxical reaction, reaction time slowed[Ref]


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

Common (1% to 10%): Confusion/confusional state, depression/unmasked preexisting depression, insomnia, restlessness

Uncommon (0.1% to 1%): Abnormal behavior, anxiety, delusion, loss of libido, nightmare, numbed emotions

Frequency not reported: Abuse, acute agitational states/agitation, anger, decreased libido, dependence/physical dependence/psychic dependence, difficulty falling asleep/staying asleep, euphoria, fits of rage, habituation, hallucinations, inappropriate behavior, initial insomnia, poor quality sleep, psychotic disorder/reactions, rebound phenomena, suicidal ideation, suicidal tendencies, withdrawal

Postmarketing reports: Apathy, delirium[Ref]

Dependence more commonly occurred during prolonged use.

Loss of libido was typically reversible and occurred more frequently with higher doses and/or with prolonged treatment.

Withdrawal and rebound phenomena have occurred with discontinuation of treatment.[Ref]


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

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

Very rare (less than 0.01%): Respiratory disorders

Frequency not reported: Respiratory depression, respiratory failure

Postmarketing reports: Aspiration[Ref]

Respiratory failure more commonly occurred with high doses and/or in patients with preexisting compromised respiratory function (e.g., bronchial asthma, brain damage).[Ref]


Common (1% to 10%): Constipation, diarrhea, dry mouth, dysphagia, nausea

Frequency not reported: Vomiting

Postmarketing reports: Abdominal distention, lip edema[Ref]


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

Uncommon (0.1% to 1%): Weight increased

Frequency not reported: Anorexia[Ref]


Common (1% to 10%): Rash

Very rare (less than 0.01%): Cutaneous reactions, urticaria

Frequency not reported: Photosensitivity reaction, pruritus, Stevens-Johnson syndrome, sweating, toxic epidermal necrolysis (TEN)/fatal TEN

Postmarketing reports: Facial edema[Ref]


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

Postmarketing reports: Urinary retention[Ref]


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


Uncommon (0.1% to 1%): Diplopia

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

Diplopia was typically reversible and occurred more frequently with higher doses and/or at the beginning of treatment.[Ref]


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


Frequency not reported: Abnormal hematologic tests

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


Frequency not reported: Abnormal liver function tests

Postmarketing reports: Increased liver enzymes[Ref]


Postmarketing reports: Angioedema[Ref]

Frequently asked questions


1. Cerner Multum, Inc. UK Summary of Product Characteristics.

2. Cerner Multum, Inc. Australian Product Information.

3. Product Information. Frisium (clobazam). Sanofi-Aventis. 2011.

4. Product Information. Onfi (clobazam). Lundbeck Inc. 2011.

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.