Indications
Istradefylline is used in adults with Parkinson’s disease as an add-on to Levodopa (usually with Carbidopa) to reduce “off” episodes, the periods when the effect of Levodopa wears off and symptoms such as stiffness, slowness and tremor return. It is not used on its own.
How It Works
In Parkinson’s disease, the loss of dopamine leaves another brain chemical, adenosine, acting too strongly on the brain’s movement circuits. Istradefylline blocks the adenosine A2A receptors in these circuits. This rebalances the signals and helps Levodopa work for longer, without acting directly on dopamine receptors.
Dosage and Administration
Take as prescribed by your specialist. The usual adult dose is 20 mg once daily, which the doctor may increase to 40 mg once daily. People who smoke heavily may need the higher dose, and people with moderate liver problems or those taking strong CYP3A4 inhibitors should not exceed 20 mg daily. Take it at the same time each day, with or without food, and continue your Levodopa as directed.
Interactions
Strong CYP3A4 inhibitors such as Ketoconazole, Itraconazole and Clarithromycin raise istradefylline levels; strong inducers such as Rifampicin, Carbamazepine, Phenytoin and St John’s Wort should be avoided as they make it ineffective. Istradefylline can raise levels of medicines such as Atorvastatin, Midazolam and Digoxin. Smoking lowers its levels.
Contraindications
- Allergy to Istradefylline or any tablet ingredient.
- Severe liver impairment.
- Use with strong CYP3A4 inducers.
- Children and adolescents.
Side Effects
Common effects include involuntary movements (dyskinesia) or worsening of existing ones, dizziness, constipation, nausea, sleeplessness and hallucinations. Some people develop impulse-control problems, such as compulsive gambling, shopping, eating or sexual urges.
Get urgent medical help if you have severe confusion, hallucinations or paranoid thoughts, fainting, severe uncontrolled movements, or swelling of the face and difficulty breathing.
Pregnancy and Lactation
Animal studies suggest it may harm the unborn baby. It is not recommended during pregnancy, and women who can become pregnant should use effective contraception. It is not known whether it passes into breast milk; breastfeeding is not recommended.
Precautions and Warnings
Tell your doctor if you have a history of hallucinations or mental health problems, or liver disease. Your doctor may lower your Levodopa dose if involuntary movements increase. Tell your doctor about any unusual urges or behaviour; family members can help notice them. Take care when driving if you feel dizzy.
Overdose
Overdose may increase side effects such as dyskinesia, hallucinations and dizziness. There is no specific antidote; seek medical help and bring the pack.
Therapeutic Class
Antiparkinson agent, adenosine A2A receptor antagonist.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.