Clonazepam
| File:Clonazepam.jpg | |
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| Routes of administration | Oral, I.M., I.V |
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| Pharmacokinetic data | |
| Bioavailability | 90% |
| Metabolism | Hepatic CYP3A4 |
| Elimination half-life | 30-40 hours |
| Excretion | Renal |
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| ECHA InfoCard | 100.015.088 |
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| Formula | C15H10ClN3O3 |
| Molar mass | 315.715 g·mol−1 |
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 as tablets (0.25, 0.5, 1.0, and 2mg), oral wafers (0.25, 0.5, 1.0 mg), liquid solution (2.5mg per ml) and for injection (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 function
- Impaired coordination
- Impaired balance
- Dizziness
- Anterograde amnesia (common with higher doses)
Rare:
- Paradoxical Disinhibition[2] (Most frequently in children, the elderly, and in persons with developmental disabilities)
- Rage
- Excitement
- Irritability
- 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.
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 apnea
- 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-/postoperative 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 functions
- Impaired reflexes
- Impaired coordination
- Impaired balance
- 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. [1]
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.
References
- O'Brien, CP. "Benzodiazepine use, abuse, and dependence", Journal of Clinical Psychiatry. 2005;66 Suppl 2:28-33. [2]
- Wallace, Christina. "Kpin, a hit drug with teens, can be deadly, officials say." Boston Metro, Wednesday April 12, 2006. Page 2.
External links
- Rx-List - Clonazepam
- Poisons Information Monograph - Clonazepam
- Clonazepam - Prescription Drug Info Detailed Drug Profile
- FDA prescription insert
- ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 Oct 2023.
- ^ van der Bijl P, Roelofse JA. Disinhibitory reactions to benzodiazepines: a review. J Oral Maxillofac Surg 1991;49:519-23