What the label lists and what reports show
Clonazepam side effects
Clonazepam's FDA label: “The most common events (≥1%) associated with discontinuation and a dropout rate twice or greater for Klonopin than that of placebo included the following: Table 2 Most Common Adverse Events (≥1%) Associated with Discontinuation of Treatment Adverse Event …” FAERS holds 159,283 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (10,473 reports).
- Generic listed
- In shortage
- Boxed warning
- DEA Schedule IV
Check it at the source: the clonazepam FDA label on DailyMed (effective December 1, 2025, H2-Pharma, LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of KLONOPIN?See " What is the most important information I should know about KLONOPIN? " KLONOPIN can also make your seizures happen more often or make them worse. Call your healthcare provider right away if your seizures get worse while taking KLONOPIN. The most common side effects of KLONOPIN include: drowsiness problems with walking and coordination dizziness depression fatigue problems with memory These are not all the possible side effects of KLONOPIN. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. You may also report side effects to the Safety Call Center at 1-866-788-3904.
Source: FDA drug label, NDA017533 (Cheplapharm), as published by H2-Pharma, LLC, effective December 1, 2025 (SPL set cfa0d79a-843c-4b88-95a1-e9511d649ca1), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common events (≥1%) associated with discontinuation and a dropout rate twice or greater for Klonopin than that of placebo included the following: Table 2 Most Common Adverse Events (≥1%) Associated with Discontinuation of Treatment Adverse Event Klonopin (N=574) Placebo (N=294) […]
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 Klonopin and for which the incidence was greater than that…
| Adverse Event by Body System | <1mg n=96 % | 1-<2mg n=129 % | 2-<3mg n=113 % | ≥3mg n=235 % | All Klonopin Groups N=574 % | Placebo N=294 % |
|---|---|---|---|---|---|---|
| Somnolence Indicates that the p-value for the dose-trend test (Cochran-Mantel-Haenszel)… | 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 |
| 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 |
| 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 |
| Constipation | 0 | 1 | 5 | 3 | 2 | 2 |
| Appetite Decreased | 1 | 1 | 0 | 3 | 1 | 1 |
| Abdominal Pain | 2 | 2 | 2 | 0 | 1 | 1 |
| Fatigue | 9 | 6 | 7 | 7 | 7 | 4 |
| Allergic Reaction | 3 | 1 | 4 | 2 | 2 | 1 |
| Myalgia | 2 | 1 | 4 | 0 | 1 | 1 |
| Influenza | 3 | 2 | 5 | 5 | 4 | 3 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe adverse experiences for Klonopin are provided separately for patients with seizure disorders and with panic disorder. Seizure Disorders The most frequently occurring side effects of Klonopin 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.
Source: FDA drug label, NDA017533 (Cheplapharm), as published by H2-Pharma, LLC, effective December 1, 2025 (SPL set cfa0d79a-843c-4b88-95a1-e9511d649ca1), via openFDA; the full label on DailyMed
What do FAERS reports show?
159,283 reports list clonazepam among the medicines taken, each a report of something that happened, not proof the medicine caused it; 18,605 are coded as a death and 47,308 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 19 reactions below, 9 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Clonazepam: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions