Prescription Drug Information: Clonazepam (Page 3 of 6)

Carcinogenesis, Mutagenesis, Impairment of Fertility:

Carcinogenicity studies have not been conducted with clonazepam.

The data currently available are not sufficient to determine the genotoxic potential of clonazepam.

In a two-generation fertility study in which clonazepam was given orally to rats at 10 and 100 mg/kg/day (low dose approximately 5 times and 24 times the maximum recommended human dose of 20 mg/day for seizure disorder and 4 mg/day for panic disorder, respectively, on a mg/m 2 basis), there was a decrease in the number of pregnancies and in the number of offspring surviving until weaning.

Pregnancy:

Teratogenic Effects: Pregnancy Category D (see WARNINGS: Pregnancy Risks).

To provide information regarding the effects of in utero exposure to clonazepam, physicians are advised to recommend that pregnant patients taking clonazepam enroll in the NAAED Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves. Information on this registry can also be found at the website http://www.aedpregnancyregistry.org/.

Labor and Delivery:

The effect of clonazepam on labor and delivery in humans has not been specifically studied; however, perinatal complications have been reported in children born to mothers who have been receiving benzodiazepines late in pregnancy, including findings suggestive of either excess benzodiazepine exposure or of withdrawal phenomena (see WARNINGS: Pregnancy Risks).

Nursing Mothers:

Mothers receiving clonazepam should not breastfeed their infants.

Pediatric Use:

Because of the possibility that adverse effects on physical or mental development could become apparent only after many years, a benefit-risk consideration of the long-term use of clonazepam is important in pediatric patients being treated for seizure disorder (see INDICATIONS AND USAGE and DOSAGE AND ADMINISTRATION).

Safety and effectiveness in pediatric patients with panic disorder below the age of 18 have not been established.

Geriatric Use:

Clinical studies of clonazepam did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Because clonazepam undergoes hepatic metabolism, it is possible that liver disease will impair clonazepam elimination. Metabolites of clonazepam are excreted by the kidneys; to avoid their excess accumulation, caution should be exercised in the administration of the drug to patients with impaired renal function. Because elderly patients are more likely to have decreased hepatic and/or renal function, care should be taken in dose selection, and it may be useful to assess hepatic and/or renal function at the time of dose selection.

Sedating drugs may cause confusion and over-sedation in the elderly; elderly patients generally should be started on low doses of clonazepam and observed closely.

Adverse Reactions to Clonazepam

The adverse experiences for clonazepam are provided separately for patients with seizure disorders and with panic disorder.

Seizure Disorders:

The most frequently occurring side effects of clonazepam are referable to CNS depression. Experience in treatment of seizures has shown that drowsiness has occurred in approximately 50% of patients and ataxia in approximately 30%. In some cases, these may diminish with time; behavior problems have been noted in approximately 25% of patients. Others, listed by system, including those identified during postapproval use of clonazepam are:

Cardiovascular: Palpitations

Dermatologic: Hair loss, hirsutism, skin rash, ankle and facial edema

Gastrointestinal: Anorexia, coated tongue, constipation, diarrhea, dry mouth, encopresis, gastritis, increased appetite, nausea, sore gums

Genitourinary: Dysuria, enuresis, nocturia, urinary retention

Hematopoietic: Anemia, leukopenia, thrombocytopenia, eosinophilia

Hepatic: Hepatomegaly, transient elevations of serum transaminases and alkaline phosphatase

Musculoskeletal: Muscle weakness, pains

Miscellaneous: Dehydration, general deterioration, fever, lymphadenopathy, weight loss or gain

Neurologic: Abnormal eye movements, aphonia, choreiform movements, coma, diplopia, dysarthria, dysdiadochokinesis, “glassy-eyed” appearance, headache, hemiparesis, hypotonia, nystagmus, respiratory depression, slurred speech, tremor, vertigo

Psychiatric: Confusion, depression, amnesia, hallucinations, hysteria, increased libido, insomnia, psychosis (the behavior effects are more likely to occur in patients with a history of psychiatric disturbances). The following paradoxical reactions have been observed: excitability, irritability, aggressive behavior, agitation, nervousness, hostility, anxiety, sleep disturbances, nightmares and vivid dreams

Respiratory: Chest congestion, rhinorrhea, shortness of breath, hypersecretion in upper respiratory passages

Panic Disorder:

Adverse events during exposure to clonazepam were obtained by spontaneous report and recorded by clinical investigators using terminology of their own choosing. Consequently, it is not possible to provide a meaningful estimate of the proportion of individuals experiencing adverse events without first grouping similar types of events into a smaller number of standardized event categories. In the tables and tabulations that follow, CIGY dictionary terminology has been used to classify reported adverse events, except in certain cases in which redundant terms were collapsed into more meaningful terms, as noted below.

The stated frequencies of adverse events represent the proportion of individuals who experienced, at least once, a treatment-emergent adverse event of the type listed. An event was considered treatment-emergent if it occurred for the first time or worsened while receiving therapy following baseline evaluation.

Adverse Findings Observed in Short-Term, Placebo-Controlled Trials:

Adverse Events Associated with Discontinuation of Treatment:

Overall, the incidence of discontinuation due to adverse events was 17% in clonazepam compared to 9% for placebo in the combined data of two 6- to 9-week trials. The most common events (≥ 1%) associated with discontinuation and a dropout rate twice or greater for clonazepam than that of placebo included the following:

Table 2 Most Common Adverse Events (≥ 1%) Associated with Discontinuation of Treatment
Adverse Event Clonazepam (N = 574) Placebo (N = 294)
Somnolence 7% 1%
Depression 4% 1%
Dizziness 1% < 1%
Nervousness 1% 0%
Ataxia 1% 0%
Intellectual Ability Reduced 1% 0%

Adverse Events Occurring at an Incidence of 1% or More Among Clonazepam-Treated Patients:

Table 3 enumerates the incidence, rounded to the nearest percent, of treatment-emergent adverse events that occurred during acute therapy of panic disorder from a pool of two 6- to 9-week trials. Events reported in 1% or more of patients treated with clonazepam (doses ranging from 0.5 to 4 mg/day) and for which the incidence was greater than that in placebo-treated patients are included.

The prescriber should be aware that the figures in Table 3 cannot be used to predict the incidence of side effects in the course of usual medical practice where patient characteristics and other factors differ from those that prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different treatments, uses and investigators. The cited figures, however, do provide the prescribing physician with some basis for estimating the relative contribution of drug and nondrug factors to the side effect incidence in the population studied.

Table 3. Treatment-Emergent Adverse Event Incidence in 6- to 9- Week Placebo-Controlled Clinical Trials *
*
Events reported by at least 1% of patients treated with clonazepam and for which the incidence was greater than that for placebo.
Indicates that the p-value for the dose-trend test (Cochran-Mantel-Haenszel) for adverse event incidence was ≤ 0.10.
Denominators for events in gender-specific systems are: n = 240 (clonazepam), 102 (placebo) for male, and 334 (clonazepam), 192 (placebo) for female.
Clonazepam Maximum Daily Dose
Adverse Event by Body System < 1 mg n = 96 % 1- < 2 mg n = 129 % 2- < 3 mg n = 113 % ≥ 3 mg n = 235 % All Clonazepam Groups N = 574 % Placebo N = 294 %
Central & Peripheral Nervous System
Somnolence 26 35 50 36 37 10
Dizziness 5 5 12 8 8 4
Coordination Abnormal 1 2 7 9 6 0
Ataxia 2 1 8 8 5 0
Dysarthria 0 0 4 3 2 0
Psychiatric
Depression 7 6 8 8 7 1
Memory Disturbance 2 5 2 5 4 2
Nervousness 1 4 3 4 3 2
Intellectual Ability Reduced 0 2 4 3 2 0
Emotional Lability 0 1 2 2 1 1
Libido Decreased 0 1 3 1 1 0
Confusion 0 2 2 1 1 0
Respiratory System
Upper Respiratory Tract Infection 10 10 7 6 8 4
Sinusitis 4 2 8 4 4 3
Rhinitis 3 2 4 2 2 1
Coughing 2 2 4 0 2 0
Pharyngitis 1 1 3 2 2 1
Bronchitis 1 0 2 2 1 1
Gastrointestinal System
Constipation 0 1 5 3 2 2
Appetite Decreased 1 1 0 3 1 1
Abdominal Pain 2 2 2 0 1 1
Body as a Whole
Fatigue 9 6 7 7 7 4
Allergic Reaction 3 1 4 2 2 1
Musculoskeletal
Myalgia 2 1 4 0 1 1
Resistance Mechanism Disorders
Influenza 3 2 5 5 4 3
Urinary System
Micturition Frequency 1 2 2 1 1 0
Urinary Tract Infection 0 0 2 2 1 0
Vision Disorders
Blurred Vision 1 2 3 0 1 1
Reproductive Disorders
Female
Dysmenorrhea 0 6 5 2 3 2
Colpitis 4 0 2 1 1 1
Male
Ejaculation Delayed 0 0 2 2 1 0
Impotence 3 0 2 1 1 0

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