Brand names Brocadopa, Larodopa
Used in the following combined preparations Madopar, Sinemet.
General Information
The treatment of Parkinson’s disease underwent dramatic change in the 1960s with the introduction of levodopa. Since the body can transform levodopa into dopamine, a chemical in the brain the absence or shortage of which causes Parkinson’s disease (see p.87), rapid improvements were expected. These expectations focused not so much on a cure of the disease as on the relief of symptoms.
However, it was found that, while effective, levodopa produced severe
side effects, such as nausea, dizziness, and palpitations. Even when treatment was initiated gradually, it was difficult to balance the benefits against the adverse reactions. The need for increasingly larger dosages made treatment with levodopa even more difficult.
Today the drug is combined with carbidopa or benserazide, substances that enhance the effects of levodopa in the brain, enabling lower doses to be given. This also helps to reduce the side effects of levodopa.
INFORMATION FOR USERS
Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.
How taken
Tablets, capsules.
Frequency and timing of doses
3-6 x daily with food or milk.
Adult dosage range
125-500mg initially, increased until benefits and side effects are balanced.
Onset of effect
Within 1 hour.
Duration of action
2-12 hours.
Diet advice
None.
Storage
Keep in a closed container in a cool, dry place out of the reach of children. Protect from light.
Missed dose
Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.
Stopping the drug
Do not stop taking the drug without consulting your doctor; stopping the drug may lead to worsening of the underlying condition.
Exceeding the dose
An occasional unintentional extra dose is unlikely to cause problems. Larger overdoses may cause vomiting or drowsiness. Notify your doctor.
POSSIBLE ADVERSE EFFECTS
Adverse effects of levodopa are closely related to dosage levels. At the start of treatment, when dosage is usually low, unwanted effects are likely to be mild.
Such effects may increase in severity as dosage is increased to boost the drug’s beneficial effects. All adverse effects of this drug should be discussed with your doctor.
INTERACTIONS
Antidepressant drugs
Levodopa may Interact with monoamine oxidase inhibitors (MAOIs) to cause a dangerous rise in blood pressure. It may also interact with tricyclic antidepressants.
Iron Absorption of levodopa may be reduced by iron.
Antipsychotic drugs may reduce the effect of levodopa.
Pyridoxine (vitamin B6)
Excessive intake of this vitamin may reduce the effect of levodopa.
QUICK REFERENCE
Drug group Drug for parkinsonism
Overdose danger rating Medium
Dependence rating Low
Prescription needed Yes
Available as generic No
SPECIAL PRECAUTIONS
Be sure to tell your doctor if:
You have heart problems.
You have long-term liver or kidney problems.
You have a lung disorder, such as asthma or bronchitis.
You have an overactive thyroid gland. You have had glaucoma.
You have a peptic ulcer.
You have diabetes.
You are taking other medications.
Pregnancy
Unlikely to be required.
Breast-feeding
Unlikely to be required.
Infants and children
Not normally used in children.
Over 60
No special problems.
Driving and hazardous work
Your underlying condition, as well as the possibility of levodopa causing faintness and dizziness, may make such activities inadvisable.
Discuss with your doctor.
Alcohol
No known problems.
PROLONGED USE
Effectiveness usually declines in time, necessitating increased dosage. The adverse effects become so severe that ultimately the drug must be stopped.
