Most Common Side Effects of Levodopa and Carbidopa
The most common side effects of carbidopa and levodopa therapy include dyskinesias (such as choreiform, dystonic, and other involuntary movements) and nausea. 1, 2
Gastrointestinal Side Effects
- Nausea (one of the most frequently reported adverse effects) 1, 2
- Dark saliva
- Gastrointestinal bleeding
- Development of duodenal ulcer
- Anorexia
- Vomiting
- Diarrhea
- Constipation
- Dyspepsia (indigestion)
- Dry mouth
- Taste alterations
- Abdominal pain and distress
- Dysphagia (difficulty swallowing)
- Sialorrhea (excessive salivation)
- Flatulence
- Bruxism (teeth grinding)
- Burning sensation of the tongue
- Heartburn
- Hiccups
Neurological and Psychiatric Side Effects
- "On-off" phenomenon (bradykinetic episodes) 1, 2
- Psychotic episodes including delusions and hallucinations
- Paranoid ideation
- Confusion
- Agitation
- Dizziness
- Somnolence (drowsiness)
- Dream abnormalities including nightmares
- Insomnia
- Paresthesia (tingling sensations)
- Headache
- Depression (with or without suicidal tendencies)
- Dementia
- Pathological gambling
- Increased libido including hypersexuality
- Impulse control symptoms
- Ataxia (lack of muscle coordination)
- Falling
- Anxiety
- Gait abnormalities
- Nervousness
- Decreased mental acuity
- Memory impairment
- Disorientation
- Euphoria
Cardiovascular Side Effects
- Cardiac irregularities
- Hypotension
- Orthostatic hypotension
- Hypertension
- Syncope (fainting)
- Phlebitis
- Palpitation
- Myocardial infarction (heart attack)
Skin and Related Side Effects
- Rash
- Increased sweating
- Alopecia (hair loss)
- Dark sweat
- Malignant melanoma
- Flushing
- Angioedema
- Urticaria (hives)
- Pruritus (itching)
- Henoch-Schönlein purpura
- Bullous lesions (including pemphigus-like reactions)
Other Common Side Effects
- Dyskinesia (one of the most common side effects) 1, 2, 3
- Chest pain
- Asthenia (weakness)
- Back pain
- Shoulder pain
- Muscle cramps
- Dyspnea (shortness of breath)
- Upper respiratory infection
- Urinary tract infection
- Urinary frequency
- Dark urine
- Urinary retention
- Urinary incontinence
- Priapism
- Edema
- Weight gain or weight loss
Laboratory Abnormalities
- Decreased hemoglobin and hematocrit
- Abnormalities in alkaline phosphatase, AST, ALT, LDH, bilirubin, BUN
- Positive Coombs test
- Elevated serum glucose
- White blood cells, bacteria, and blood in the urine
- Decreased white blood cell count and serum potassium
- Increased serum creatinine and uric acid
- Protein and glucose in urine
Important Considerations
- The incidence of adverse effects is often dose-dependent, with higher doses associated with increased frequency of side effects 4
- Extended-release formulations of carbidopa/levodopa may help reduce motor fluctuations compared to immediate-release formulations 3
- Long-term levodopa therapy may lead to increased risk of dyskinesia, wearing-off effect, on-off phenomenon, mental symptoms, and frozen gait 5
- The stage of Parkinson's disease and dosage of levodopa have significant influence on the development of adverse reactions 5
Monitoring Recommendations
- Regular assessment for motor fluctuations and dyskinesias
- Monitoring for psychiatric symptoms, especially hallucinations and impulse control disorders
- Checking for orthostatic hypotension (drop in blood pressure upon standing)
- Monitoring for gastrointestinal side effects, particularly nausea
- Observing for signs of skin reactions or hypersensitivity
By understanding these common side effects, clinicians can better manage patients on levodopa and carbidopa therapy, potentially improving treatment adherence and quality of life.