Clonazepam

Clonazepam (marketed by Roche under the trade-names Klonopin in the United States and Rivotril in Europe, South America, Canada, and Australia) is a drug which is a benzodiazepine derivative. It is a highly potent anticonvulsant, amnestic and anxiolytic.

Pharmacology

Like other benzodiazepines, clonazepam is believed to act by simulating the action of GABA on the central nervous system. Because of strong anxiolytic properties and euphoric side-effects it is said to be among the class of 'highly potent' benzodiazepines. Although benzodiazepines are invaluable in the treatment of anxiety disorders, they have some potential for abuse and may cause dependence or addiction. The sedative effects of clonazepam are relatively weak, compared to its strong anxiolytic and anticonvulsant effects. One quarter of a milligram (0.25mg) of clonazepam is approximately equivalent to five milligrams (5.00mg) of diazepam.

Indications

Clonazepam is commonly prescribed for:

  • Epilepsy.
  • Anxiety disorder. Due to the chronic nature of anxiety, long-term low-dose benzodiazepine treatment may be necessary for some patients; this continuation of treatment should not be considered abuse or addiction.
  • Panic attacks
  • Restless leg syndrome (RLS)
  • Inital treatment of mania, together with firstline-drugs such as lithium, haloperidol or risperidone
  • Hallucinogen persisting perception disorder (off-label use)
  • Chronic fatigue syndrome
  • Night terrors
  • Tourette Syndrome - Clonazepam has shown to be helpful in reducing and dealing with the physical motor tics associated with TS, though is still considered an off-label usage by many.

    • Clonazepam is rarely used as a treatment for insomnia, because its sedative effects are relatively weak compared to other benzodiazepines.

    Availability

    Clonazepam was approved in the United States as a generic medication in 1997 and is now manufactured and marketed by several companies.

    Clonazepam is available in the following forms:

  • Tablets: 0.25, 0.5, 1.0, and 2mg
  • Liquid concentrate: 2.5mg per ml
  • Oral wafers: 0.25, 0.5, 1.0 mg
  • Injection concentrate: 1mg per ml

    • Dosage

    Epilepsy

  • Treatment: For an epileptic seizure, 1mg given intravenously every 10 to 20 minutes until symptoms subside.
  • Prevention: Oral doses from 1 mg to 20 mg per day.

    • Clonazepam can be useful for long-term treatment of some petit-mal forms of epilepsy in children and adolescents (adults may also respond well). Up to 30% of epileptic patients treated with clonazepam develop a serious tolerance to the anticonvulsant effects. This may require dose increases or gradual withdrawal and replacement of the drug.

    Other

  • Anxiety and panic disorders - 1mg to 10mg daily, in divided doses
  • Restless Legs Syndrome - 1mg to 2mg at bedtime
  • Mania - Up to 20mg daily, in divided doses

    • Side effects

    Common:

  • Drowsiness
  • Impaired motor functiono Impaired coordinationo Impaired balanceo Dizziness
  • Anterograde amnesia (common with higher doses)

    Rare:

  • Paradoxical Disinhibition (Most frequently in children, the elderly, and in persons with developmental disabilities)o Rageo Excitemento Irritabilityo Impulsivity

    Withdrawal-related:

  • Anxiety, irritability, insomnia
  • Panic attacks, tremor
  • Seizures similar to delirium tremens (With long-term use of excessive doses)

    Use of alcohol or other CNS depressants while taking clonazepam greatly intensifies the effects (and side effects) of the drug. Side effects of the drug itself are generally benign, but sudden withdrawal after long-term use can cause severe, even fatal symptoms.

    Interactions

    Similar to Diazepam. A notable difference is that clonazepam is not affected by graprefruit juice and other inhibitors of enzyme CYP3A4.

    Contraindications

    Use of clonazepam should be avoided in individuals with the following conditions:

  • Myasthenia gravis
  • Acute intoxication with alcohol, narcotics, or other psychoactive substances
  • Ataxia
  • Severe hypoventilation
  • Acute narrow-angle glaucoma
  • Severe liver deficiencies (hepatitis and liver cirrhosis decrease elimination by a factor of 2)
  • Severe sleep apnoea
  • Hypersensitivity or allergy to any drug in the benzodiazepine class

    • Special Caution Needed

  • Children and adolescents (less than 18 years of age) - Treatment usually not indicated, except treatment of epilepsy, and pre-/post-operative treatment; extended clinical data for this age group is currently lacking.
  • I.V. or I.M. injections in hypotensive individuals or those in shock should be administered carefully and vital signs should be monitored. Like diazepam, careful monitoring for toxicity is required during prolonged I.V. usage due to the drugs long half life and rapid lipid redistribution.

    • Patients at a High Risk for Abuse and Dependence

    At a high risk for misuse, abuse, and dependence are:

  • Patients with a history of alcohol or drug abuse or dependence
  • Emotionally unstable patients
  • Patients with severe personality disorders, such as Borderline Personality Disorder
  • Patients with chronic pain or other physical disorders

    Long-term treatment with clonazepam should never be discontinued abruptly. It should be withdrawn gradually over a period of weeks or months.

    Overdose

    An individual who has consumed too much clonazepam will display one or more of the following symptoms:

  • Somnolence (difficulty staying awake)
  • Mental confusion
  • Hypotension
  • Impaired motor functionso Impaired reflexeso Impaired coordinationo Impaired balanceo Dizziness
  • Coma

    Unless combined with other drugs, deep coma or other manifestations of severe central nervous system depression are rare, and the mortality rate associated with poisoning is very low. As with other benzodiazepines, overdose symptoms of clonazepam may be reversed with flumazenil (Anexate®).

    Abuse Potential

    Although benzodiazepines are invaluable in the treatment of anxiety disorders, they have some potential for abuse and may cause dependence or addiction. It is important to distinguish between addiction to and normal physical dependence on benzodiazepines. Recreational users of benzodiazepines usually have other substance abuse problems. Benzodiazepines are usually a secondary drug of abuse-used mainly to augment the high received from another drug or to offset the adverse effects of other drugs. Few cases of addiction arise from legitimate use of benzodiazepines.

    Up to 30% of individuals treated on a long-term basis develop a form of dependence known as "low-dose-dependence". These patients do not develop a tolerance, and do not need increasingly large doses to experience the euphoric side effects of the drug.

    Legal Status

    Clonazepam is a Schedule IV drug in the United States, and possession is illegal without a prescription.

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