The following have been observed.
Frequencies are defined according to the following convention: very common (≥1/10), common (≥1/100 to <1/10), uncommon (≥1/1,000 to <1/100), rare (≥1/10,000 to <1/1,000), very rare (<1/10,000), not known (cannot be estimated from the available data).
Immune system disorders
Allergic reactions and very rare cases of anaphylaxis have been reported to occur with benzodiazepines. Angioedema may occur in rare cases.
Endocrine disorders
Isolated cases of reversible development of premature secondary sex characteristics in children (incomplete precocious puberty) have been reported.
Psychiatric disorders
Impaired concentration, restlessness, confusional state and disorientation have been observed. Depression may occur in patients treated with clonazepam, but it may be also associated with the underlying disease.
The following paradoxical reactions have been observed: excitability, irritability, aggression, agitation, nervousness, hostility, anxiety, sleep disturbances, nightmares, vivid dreams and psychotic disorders and activation of new types of seizures may be precipitated. If these occur, the benefit of continuing the drug should be weighed against the adverse effect. The addition to the regimen of another suitable drug may be necessary or, in some cases, it may be advisable to discontinue clonazepam therapy.
Dependence (see section 4.4)
In rare cases loss of libido may occur.
Nervous system disorders
Somnolence, slowed reaction, muscular hypotonia, dizziness and ataxia. These undesirable effects occur relatively frequently and are usually transient and generally disappear spontaneously in the course of the treatment or on reduction of the dosage. They can be partially prevented by increasing the dose slowly at the start of treatment.
Headache was observed in rare cases. Causing of generalised fits was observed very rarely.
Particularly in long-term or high-dose treatment, reversible disorders such as a slowing or slurring of speech (dysarthria), reduced coordination of movements and gait disorder (ataxia) and nystagmus may occur. Anterograde amnesia may occur using benzodiazepines at therapeutic dosages, the risk increasing at higher dosages. Amnestic effects may be associated with inappropriate behaviour.
With certain forms of epilepsy, an increase in the frequency of seizures during long- term treatment is possible.
Although clonazepam has been given uneventfully to patients with porphyria, rarely it may induce convulsions in these patients.
Eye disorders
Particularly in long-term or high-dose treatment, reversible disorders of vision (diplopia) may occur.
Common: nystagmus
Cardiac Disorders
Cardiac failure including cardiac arrest has been reported.
Respiratory, thoracic and mediastinal disorders
Rarely respiratory depression may occur, particularly on intravenous administration of clonazepam. This effect may be aggravated by pre-existing airways obstruction or brain damage or if other medications which depress respiration have been given. As a rule, this effect can be avoided by careful adjustment of the dose to individual requirements.
In infants and small children, and particularly those with a degree of mental impairment, clonazepam may give rise to salivary or bronchial hypersecretion with drooling. Supervision of the airway may be required.
Gastrointestinal disorders
The following effects have been reported in rare cases: nausea, gastrointestinal and epigastric symptoms
Skin and subcutaneous tissue disorders
The following effects may occur in rare cases: urticaria, pruritus, rash, transient hair loss and pigmentation changes.
Musculoskeletal and connective tissue disorders
Muscle weakness, this undesirable effect occurs relatively frequently and is usually transient and generally disappears spontaneously in the course of the treatment or on reduction of the dosage. It can be partially prevented by increasing the dose slowly at the start of the treatment.
Renal and urinary disorders
In rare cases urinary incontinence may occur.
Reproductive System and breast disorders
In rare cases erectile dysfunction or loss of libido may occur.
General disorders and administration site conditions
Fatigue (tiredness, lassitude), this undesirable effect occurs relatively frequently and is usually transient and generally disappears spontaneously in the course of the treatment or on reduction of the dosage. It can be partially prevented by increasing the dose slowly at the start of treatment.
Withdrawal reactions (see section 4.4)
Investigations
In rare cases decreased platelet count may occur. As with other benzodiazepines, isolated cases of blood dyscrasias and abnormal liver function tests have been reported.
Injury, poisoning and procedural complications
There have been reports of falls and fractures in benzodiazepine users. The risk is increased in those taking concomitant sedatives (including alcoholic beverages) and in the elderly.
Paediatric population
For paediatric specific events please refer to the information listed under headings: Endocrine Disorders and Respiratory, Thoracic and Mediastinal System Disorders in section 4.8.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.