Applies to dextromethorphan / quinidine: oral capsule.
Serious side effects
Along with its needed effects, dextromethorphan/quinidine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking dextromethorphan / quinidine:
Less common
- Bladder pain
- bloating or swelling of the face, arms, hands, lower legs, or feet
- bloody or cloudy urine
- chills
- cough
- diarrhea
- difficult, burning, or painful urination
- fever
- frequent urge to urinate
- general feeling of discomfort or illness
- headache
- joint pain
- loss of appetite
- lower back or side pain
- muscle aches and pains
- nausea
- rapid weight gain
- runny nose
- shivering
- sore throat
- sweating
- tingling of the hands or feet
- trouble sleeping
- unusual tiredness or weakness
- unusual weight gain or loss
- vomiting
Get emergency help immediately if any of the following symptoms of overdose occur while taking dextromethorphan / quinidine:
Symptoms of overdose
- Aggressive and violent behavior
- agitation
- blurred vision
- change in color vision
- change in consciousness
- chest pain or discomfort
- confusion
- confusion as to time, place, or person
- continuing ringing or buzzing or other unexplained noise in the ears
- decreased awareness or responsiveness
- depression
- difficulty seeing at night
- dizziness or lightheadedness
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- double vision
- excitement
- fainting
- fast, pounding, or irregular heartbeat or pulse
- feeling of constant movement of self or surroundings
- hallucinations
- hearing loss
- holding false beliefs that cannot be changed by fact
- inability to move the eyes
- increased blinking or spasms of the eyelid
- increased sensitivity of the eyes to sunlight
- irregular or slow heart rate
- loss of consciousness
- overactive reflexes
- poor coordination
- restlessness
- seeing double
- seizures
- sensation of spinning
- severe sleepiness
- shakiness and unsteady walk
- shivering
- shortness of breath
- sticking out of tongue
- sweating
- talking or acting with excitement you cannot control
- trembling or shaking
- trouble with breathing, speaking, or swallowing
- twitching
- uncontrolled eye movements
- uncontrolled twisting movements of the neck, trunk, arms, or legs
- unsteadiness, trembling, or other problems with muscle control or coordination
- unusual excitement, nervousness, or restlessness
- unusual facial expressions
Other side effects
Some side effects of dextromethorphan / quinidine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Less common
- Bloated
- excess air or gas in the stomach or intestines
- full feeling
- lack or loss of strength
- passing gas
For Healthcare Professionals
Applies to dextromethorphan / quinidine: oral capsule.
General
The most commonly reported adverse reactions (2% or greater incidence and greater than placebo) that led to treatment discontinuation were muscle spasticity, abdominal pain, asthenia, dizziness, muscle spasms, respiratory failure, and fall.[Ref]
Gastrointestinal
Very common (10% or more): Diarrhea (13%)
Common (1% to 10%): Abdominal pain, vomiting, flatulence
Dextromethorphan:
Postmarketing reports: Nausea, vomiting, stomach pain[Ref]
Nervous system
Very common (10% or more): Dizziness (10%)
Dextromethorphan:
Postmarketing reports: Drowsiness, dizziness, nervousness, restlessness
Quinidine:
Postmarketing reports: Convulsions, apprehension, ataxia, acute psychotic reactions (rare)[Ref]
Cardiovascular
Frequency not reported: QTc prolongation[Ref]
Musculoskeletal
Common (1% to 10%): Muscle spasticity, muscle spasms[Ref]
Hepatic
Common (1% to 10%): Increased gamma-glutamyltransferase[Ref]
Respiratory
Common (1% to 10%): Respiratory failure, cough[Ref]
Other
Common (1% to 10%): Asthenia, fall, peripheral edema
Quinidine:
Postmarketing reports: Cinchonism[Ref]
Cinchonism is usually a sign of chronic quinidine toxicity, but it may appear in sensitive patients after a single moderate dose of several hundred milligrams. It is characterized by nausea, vomiting, diarrhea, tinnitus headache, hearing loss, vertigo, blurred vision, diplopia, photophobia, confusion, and delirium.[Ref]
Immunologic
Common (1% to 10%): Influenza[Ref]
Genitourinary
Common (1% to 10%): Urinary tract infection[Ref]
Ocular
Quinidine:
Postmarketing reports: Mydriasis, disturbed color perception, night blindness, scotomata, optic neuritis, visual field loss, photosensitivity, keratopathy[Ref]
Dermatologic
Quinidine:
Postmarketing reports: Skin pigmentation abnormalities[Ref]
Psychiatric
Quinidine:
Postmarketing reports: Depression[Ref]
