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Onfi Side Effects

Generic Name: clobazam

Note: This page contains side effects data for the generic drug clobazam. It is possible that some of the dosage forms included below may not apply to the brand name Onfi.

In Summary

Common side effects of Onfi include: constipation, drowsiness, fever, sedation, aggressive behavior, ataxia, lethargy, drooling, and irritability. Other side effects include: pneumonia, urinary tract infection, cough, bronchitis, dysarthria, dysphagia, fatigue, insomnia, decreased appetite, and increased appetite. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to clobazam: oral suspension, oral tablet

As well as its needed effects, clobazam (the active ingredient contained in Onfi) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking clobazam, check with your doctor immediately:

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
  • 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

Minor Side Effects

Some clobazam side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common:
  • Aggressive
  • body aches or pain
  • decreased appetite
  • difficulty having a bowel movement (stool)
  • 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
  • rash, hives, or welts
  • red skin
  • swelling of the stomach area

For Healthcare Professionals

Applies to clobazam: oral suspension, oral tablet


The most commonly reported side effects were somnolence, lethargy, drooling, and ataxia.[Ref]


Very common (10% or more): Aggression (up to 14%)
Common (1% to 10%): Insomnia, irritability, depression
Uncommon (0.1% to 1%): Decreased libido or loss of libido, euphoria, numbed emotions, preexisting depression may be unmasked during benzodiazepine use
Frequency not reported: Withdrawal symptoms, physical and psychological dependence, suicidal behavior and ideation
Postmarketing reports: Agitation, anxiety, apathy, confusional state, delirium, delusion, hallucination[Ref]

Nervous system

Very common (10% or more): Somnolence ( up to 32%), lethargy (up to 15%), drooling ( up to 14%), ataxia (up to 10%)
Common (1% to 10%): Sedation, psychomotor hyperactivity, dysarthria, dizziness, headache, confusion, slurred speech, tremor
Uncommon (0.1% to 1%): Anterograde amnesia, amnesia
Frequency not reported: Potentiation of sedation from concomitant use with central nervous system depressants[Ref]


Common (1% to 10%): Rash
Uncommon (0.1% to 1%): Sweating
Postmarketing reports: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), urticaria, angioedema, facial and lip edema[Ref]


Postmarketing reports: Increased hepatic enzyme[Ref]


Very common (10% or more): Upper respiratory tract infection (up to 14%)
Common (1% to 10%): Pneumonia, bronchitis, cough
Uncommon (0.1% to 1%): Respiratory depression
Postmarketing reports: Aspiration, respiratory depression[Ref]


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


Very common (10% or more): Constipation (10%)
Common (1% to 10%): Vomiting, dysphagia, dry mouth, diarrhea, nausea
Postmarketing reports: Abdominal distention[Ref]


Common (1% to 10%): Urinary tract infection
Postmarketing reports: Urinary retention[Ref]


Common (1% to 10%): Increased appetite, decreased appetite
Uncommon (0.1% to 1%): Anorexia[Ref]


Uncommon (0.1% to 1%): Muscle aches, weakness, stiffness, spasm[Ref]


Frequency not reported: Nystagmus
Postmarketing reports: Diplopia, vision blurred[Ref]


Very common (10% or more): Pyrexia ( up to 17%), irritability (up to 11%)
Common (1% to 10%): Fatigue
Uncommon (0.1% to 1%): Hangover
Postmarketing reports: Hypothermia[Ref]


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


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

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

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

It is possible that some side effects of Onfi may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.