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).
The side effects marked with an asterisk (*) are usually transitory and disappear spontaneously as treatment continues or with dose reduction. They tend to occur early in treatment and can be greatly reduced, if not avoided, by commencing with low dosages followed by progressive increases.
Blood and the lymphatic system disorders
Isolated cases of blood dyscrasias.
Immune system disorders
Allergic reaction and a very few cases of anaphylaxis and angioedema.
Endocrine disorders
Isolated cases of reversible development of premature secondary sex characteristics in children (incomplete precocious puberty) have been reported.
Psychiatric disorders and Paradoxical Reactions
Anterograde amnesia (risk increases at higher dosages). Amnestic effects may be associated with inappropriate behaviour. Depression, loss of libido, impotence.
Use of benzodiazepines may lead to the development of physical and psychological dependence upon these products. The risk of dependence increases with dose and duration of treatment and is particularly pronounced in predisposed patients with a history of alcoholism or drug abuse (see section 4.4).
Paradoxical effects such as aggressiveness, excitability, nervousness, hostility, anxiety, sleep disturbances, nightmares, vivid dreams, irritability, agitation, psychotic disorders and activation of new types of seizures may occur. If these occur, the benefit of continuing the drug should be weighed against the adverse effect. It may be necessary to add another suitable drug to the regimen or to discontinue clonazepam therapy.
Nervous system disorders
Dizziness*, light-headedness*, somnolence*, fatigue*, co-ordination disturbances*, poor concentration, restlessness, confusion and disorientation, headache.
Dysarthria and ataxia* are reversible disorders and occur particularly in long-term or high-dose treatment.
These undesirable effects occur relatively frequently and may disappear gradually 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 generalized fits was observed very rarely.
Particularly in long-term or high-dose treatment, reversible disorders such as 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 behavior. Although clonazepam has been given uneventfully to patients with porphyria, rarely it may induce convulsions in these patients.
With certain forms of epilepsy, an increase in the frequency of seizures during long term treatment is possible.
Rarely, convulsions may be induced in patients with porphyria.
Eye disorders
Double vision and nystagmus are reversible disorders and occur particularly in long term or high-dose treatment.
Common: nystagmus
Cardiac Disorders
Cardiac failure including cardiac arrest has been reported.
Respiratory, thoracic and mediastinal disorders
Rarely respiratory depression may occur with intravenous clonazepam, particularly if other depressant drugs have been administered. This effect may be aggravated by pre- existing airways obstruction or brain damage or if other medications which depress respiration have been given. This effect can usually 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, salivary or bronchial hypersecretion with drooling may occur. Supervision of the airway may be required.
Gastrointestinal disorders
Rarely: nausea, gastrointestinal and epigastric symptoms.
Hepato-biliary disorders
Isolated cases of abnormal liver function tests have been reported.
Skin and subcutaneous tissue disorders
Rarely: urticaria, pruritus, rash, transient hair loss, pigmentation changes.
Musculoskeletal, connective tissue and bone disorders
Muscle weakness*, occasional muscular hypotonia*
Renal and urinary disorders
Rarely: urinary incontinence.
Reproductive System and Breast Disorders
In rare cases erectile dysfunction or loss of libido may occur.
General disorders and administration site conditions
Withdrawal: Once physical dependence has developed, abrupt termination of treatment will be accompanied by withdrawal symptoms. During long-term treatment, withdrawal symptoms may develop, especially withdrawing from high doses or if the daily dose is reduced rapidly or abruptly discontinued. The symptoms include: tremor, sweating, agitation, sleep disturbances and anxiety, headaches, muscle pain, extreme anxiety, tension, restlessness, confusion, irritability and epileptic seizures which may be associated with the underlying disease. In severe cases the following symptoms may occur: derealisation, depersonalisation, hyperacusis, numbness and tingling of the extremities, hypersensitivity to light, noise and physical contact or hallucinations. Since the risk of withdrawal symptoms is greater after abrupt discontinuation of treatment, discontinuation should be carried out by gradually reducing the daily dose.
Injury, Poisoning and Procedural Complications
An increased risk for falls and fractures has been reported in elderly benzodiazepine users. The risk is increased in those taking concomitant sedatives (including alcoholic beverages)
Investigations
In rare cases decreased platelet count may occur. As with other benzodiazepines, isolated cases of blood dyscrasias. Dependence and withdrawal, (see section 4.4).
Pediatric population
For pediatric 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; website www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.