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Klonopin Side Effects

Generic Name: clonazepam

Note: This page contains information about the side effects of clonazepam. Some of the dosage forms included on this document may not apply to the brand name Klonopin.

Not all side effects for Klonopin may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to clonazepam: oral solution, oral tablet, oral tablet disintegrating

In addition to its needed effects, some unwanted effects may be caused by clonazepam (the active ingredient contained in Klonopin). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking clonazepam:

More common
  • Body aches or pain
  • chills
  • cough
  • difficulty with breathing
  • discouragement
  • dizziness
  • ear congestion
  • feeling sad or empty
  • fever
  • headache
  • irritability
  • lack of appetite
  • loss of interest or pleasure
  • loss of voice
  • nasal congestion
  • poor coordination
  • runny nose
  • shakiness and unsteady walk
  • sleepiness or unusual drowsiness
  • sneezing
  • sore throat
  • tiredness
  • trouble with concentrating
  • trouble with sleeping
  • unsteadiness, trembling, or other problems with muscle control or coordination
  • unusual tiredness or weakness
Less common
  • Being forgetful
  • bladder pain
  • bloody or cloudy urine
  • changes in patterns and rhythms of speech
  • diarrhea
  • difficult, burning, or painful urination
  • frequent urge to urinate
  • general feeling of discomfort or illness
  • joint pain
  • loss of appetite
  • lower back or side pain
  • mood or mental changes
  • muscle aches and pains
  • nausea
  • nervousness
  • problems in urination or increase in the amount of urine
  • shivering
  • slurred speech
  • sore throat
  • sweating
  • trouble with speaking
  • vomiting
  • Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • changes in skin color
  • chest pain or discomfort
  • cold sweats
  • colds
  • confusion
  • cough or hoarseness
  • difficulty with sleeping
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position
  • excessive dreaming
  • excessive muscle tone
  • excitement
  • falling
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling mad
  • feeling of unreality
  • flu-like symptoms
  • headache, severe and throbbing
  • lack of feeling or emotion
  • lack or loss of self-control
  • muscle stiffness
  • muscle tension or tightness
  • nightmares
  • pain, inflammation, or swelling in the calves, shoulders, or hands
  • pain or swelling in the arms or legs without any injury
  • pain, tenderness, or swelling of the foot or leg
  • partial or slight paralysis
  • scaling
  • sense of detachment from self or body
  • shakiness in the legs, arms, hands, or feet
  • shortness of breath
  • skin rash
  • sleeplessness
  • swelling around the eyes
  • swelling of the face, ankle, foot, or knees
  • thoughts of killing oneself changes in behavior
  • tightness in the chest
  • trembling or shaking of the hands or feet
  • troubled breathing
  • unable to sleep
  • uncaring
  • vision changes
  • wheezing
Incidence not known
  • Anxiety
  • black, tarry stools
  • bleeding gums
  • blood in the urine or stools
  • change in consciousness
  • chest congestion
  • difficulty with coordination
  • double vision
  • drowsiness
  • dry mouth
  • feeling that others are watching you or controlling your behavior
  • feeling that others can hear your thoughts
  • feeling, seeing, or hearing things that are not there
  • hyperventilation
  • irregular, fast, slow, or shallow breathing
  • irregular, twisting uncontrolled movement of the face, hands, arms, or legs
  • loss of consciousness
  • loss of interest or pleasure
  • loss of memory
  • loss of strength or energy
  • loss of voice
  • muscle weakness
  • pale or blue lips, fingernails, or skin
  • pinpoint red spots on the skin
  • problems with memory
  • restlessness
  • right upper abdominal pain and fullness
  • severe mood or mental changes
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • troubled breathing with exertion
  • uncontrolled eye movements
  • unusual behavior
  • unusual bleeding or bruising
  • unusual weak feeling
  • vivid dreams
  • weight loss or gain

Some of the side effects that can occur with clonazepam may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common
  • Decreased interest in sexual intercourse
  • difficulty with swallowing
  • dryness or soreness of the throat
  • heavy bleeding
  • hives
  • inability to have or keep an erection
  • longer than usual time to ejaculation of semen
  • loss in sexual ability, desire, drive, or performance
  • pain or tenderness around the eyes and cheekbones
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • voice changes
  • Acid or sour stomach
  • ankle, knee, or great toe joint pain
  • belching
  • bleeding after defecation
  • blistering, burning, crusting, dryness, or flaking of the skin
  • bloated
  • blurred or loss of vision
  • decrease or change in vision
  • difficulty with moving
  • disturbed color perception
  • double vision
  • dryness of the eyes
  • earache
  • excess air or gas in stomach or intestines
  • feeling of constant movement of self or surroundings
  • feeling of warmth
  • frequent bowel movements
  • full feeling
  • hair loss or thinning of the hair
  • halos around lights
  • heartburn
  • increased watering of the mouth
  • indigestion
  • irregularities in menstruation
  • itching in genital or other skin areas
  • itching, scaling, severe redness, soreness, or swelling of the skin
  • joint stiffness or swelling
  • leg or muscle cramps
  • loss of taste
  • night blindness
  • nosebleeds
  • overbright appearance of lights
  • pain in the breasts or pelvic area
  • pain in the leg, nape, or back
  • passing gas
  • red, sore eyes
  • redness of the face, neck, arms, and occasionally, upper chest
  • redness or swelling in the ear
  • sensation of spinning
  • skin rash cracks in the skin at the corners of the mouth
  • smaller amount of semen ejaculated than usual
  • sore on the edge of the eyelid
  • soreness or redness around the fingernails and toenails
  • stomach discomfort, upset, or pain
  • thickening of the tongue
  • thirst
  • tooth disorder
  • toothache
  • tunnel vision
  • twitching of the eyes
  • uncomfortable swelling around the anus
  • worsening of acne
Incidence not known
  • Burning feeling in the chest or stomach
  • difficulty having a bowel movement (stool)
  • increased appetite
  • increased hair growth, especially on the face
  • increased in sexual ability, desire, drive, or performance
  • increased interest in sexual intercourse
  • sore gums
  • tenderness in the stomach area

For Healthcare Professionals

Applies to clonazepam: oral tablet, oral tablet disintegrating


The most commonly reported side effects were drowsiness, ataxia, and behavioral problems.[Ref]


Common (1% to 10%): Depression, emotional lability, confusion
Frequency not reported: Hallucinations, hysteria, insomnia, psychosis, excitability, irritability, aggressive behavior, agitation, hostility, anxiety, vivid dreams, hyperactivity, hypoesthesia, organic disinhibition, depersonalization, apathy, excitement, feeling mad, illusion, nightmares, sleep disorders, suicide ideation[Ref]

Nervous system

Very common (10% or more): Somnolence (up to 50%), Dizziness (up to 12%)
Common (1% to 10%): Nervousness, ataxia, reduced intellectual ability, abnormal coordination, dysarthria, memory disturbance
Frequency not reported: Aphonia, choreiform movements, coma, dysdiadochokinesis, "glassy-eyed" appearance, headache, hemiparesis, hypotonia, nystagmus, slurred speech, tremor, vertigo, taste loss, migraine, paresthesia[Ref]


Common (1% to 10%): Allergic Reaction[Ref]


Frequency not reported: Hepatomegaly, transient elevations of serum transaminases and alkaline phosphatase[Ref]


Common (1% to 10%): Fatigue
Frequency not reported: Ankle edema, facial edema, periorbital edema, general deterioration, fever, wound, shivering, malaise, pain, localized inflammation, earache, motion sickness[Ref]


Common (1% to 10%): Decreased libido, increased libido, urinary tract infection, dysmenorrhea, colpitis, impotence, delayed ejaculation
Frequency not reported: Dysuria, enuresis, nocturia, urinary retention, breast pain, menstrual irregularity, dysuria, cystitis, polyuria, urinary incontinence, bladder dysfunction, urinary tract bleeding, urine discoloration[Ref]


Frequency not reported: Lymphadenopathy, anemia, leukopenia, thrombocytopenia, eosinophilia, dermal bleeding[Ref]


Common (1% to 10%): Constipation, decreased appetite, abdominal pain
Frequency not reported: Coated tongue, diarrhea, dry mouth, encopresis, gastritis, increased appetite, nausea, sore gum, abdominal discomfort, gastrointestinal inflammation, stomach upset, toothache, flatulence, pyrosis, increased saliva, tooth disorder, frequent bowel movements, pelvic pain, dyspepsia, hemorrhoids, hypersalivation[Ref]


Very common (10% or more): Upper respiratory tract infection (10%)
Common (1% to 10%): Sinusitis, rhinitis, coughing, pharyngitis, bronchitis, influenza
Frequency not reported: Respiratory depression, chest congestion, rhinorrhea, hypersecretion in upper respiratory passages, excessive sneezing, asthmatic attack, dyspnea, nosebleed, pneumonia, pleurisy[Ref]


Frequency not reported: Hair loss, hirsutism, skin rash, cellulitis, acne flare, alopecia, xeroderma, contact dermatitis, pruritus, pustular reaction, skin burns, skin disorder[Ref]


Common (1% to 10%): Blurred vision
Frequency not reported: Diplopia, eye irritation, visual disturbance, eye twitching, styes, visual field defect, xerophthalmia[Ref]


Frequency not reported: Anorexia, dehydration, weight loss/gain, thirst, gout[Ref]


Frequency not reported: Palpitations, chest pain, postural hypotension, heart rate and rhythm disorders, flushing, leg thrombophlebitis[Ref]


Frequency not reported: Reversible development of premature secondary sex
characteristics in children (incomplete precocious puberty)[Ref]


Frequency not reported: Mycotic infection, viral infection, streptococcal infection, herpes simplex infection, infectious mononucleosis, moniliasis[Ref]


Common (1% to 10%): Myalgia
Frequency not reported: Muscle weakness, back pain, traumatic fracture, sprains/ strains, leg pain, neck pain, muscle cramps, leg cramps, ankle pain, shoulder pain, tendinitis, arthralgia, hypertonia, lumbago, feet pain, jaw pain, knee pain, knee swelling[Ref]


1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

2. Cerner Multum, Inc. "Australian Product Information." O 0

3. "Product Information. Klonopin (clonazepam)." Roche Laboratories, Nutley, NJ.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.