Medication for Parkinson's disease

Three main groups of medication are used to treat Parkinson's in the early stages:

• Levodopa (L-Dopa): is converted into dopamine in the brain.
• Dopamine agonists: stimulate the nerve receptors responsible for the uptake of dopamine.
• MAO-B inhibitors (monoamine oxidase B inhibitors): block the breakdown of dopamine in the brain.

The medications are usually taken in tablet form. Some dopamine agonists are also available as patches.

In the early stages, some people with mild symptoms cope just fine without medication. If at some stage the symptoms become too much of a problem, levodopa and dopamine agonists are the main medication options. They work slightly differently to each other, and some products may cause side effects more often – or have worse side effects – than others. But both are very effective in the early stages of the illness. That helps many people with Parkinson's to live a fairly symptom-free life for at least a few years.

It's difficult to predict how successful treatment will be. The medications don't have the same effect in everyone – and it can sometimes take a while to find the right dose. A noticeable effect can generally be expected within one or two weeks of starting treatment: Movements become easier again and stiffness reduces. Those kinds of symptoms can continue to improve for up to three months after starting treatment. Tremor is often more difficult to treat. Sometimes it only goes away after months or even years of taking medication.

If the symptoms are mild, MAO-B inhibitors are sometimes considered instead. MAO-B inhibitors can relieve symptoms and delay the need to take levodopa by a few months. But they aren't as effective as levodopa or dopamine agonists, and they aren't suitable for treating more severe symptoms when used alone.

To be able to work properly, the medication should be taken at set times of the day. It's not always easy to remember to take it regularly. It can help to always take the medication when you do a certain part of your daily routine, like when you brush your teeth. Writing yourself notes or using smartphone app reminders can also be helpful.

L-Dopa shouldn't be taken less than an hour before or after eating protein-rich meals because protein-rich food can interfere with the absorption of L-Dopa into the blood. Dopamine agonists, on the other hand, are taken with meals. Taking medication at the wrong time of day can make the symptoms worse.

People often have to take more than one type of medication. If the symptoms can't be reduced enough or side effects become too strong, many people switch to a different medication or start taking another one additionally.

Treatment is often started with just one medication. Levodopa and dopamine agonists are the most effective. Both have their own advantages and disadvantages that play an important role when deciding which one to take.

Dopamine agonists are usually recommended for people under the age of 60 to 70, in order to delay the onset of movement problems. Levodopa is usually recommended for older people because it's better tolerated. Some people take a combination of levodopa and dopamine agonists from the beginning.

It is currently difficult to say which medication is best suited to the various age groups. There can be perfectly valid reasons for people under the age of 70 to start using levodopa first. Various factors other than age play a role here, such as the severity of the symptoms or concerns about particular side effects. Because of this, it's important to discuss the pros and cons of the different medications with your doctor when deciding which would be most suitable for you.

Several studies have looked into the long-term effects of the initial "levodopa vs. dopamine agonist" treatment decision. For instance, one large study showed the following after seven years:

• About 50 out of 100 people had stopped their initial treatment with dopamine agonists because the side effects were too bad or the medication wasn't effective enough.
• In comparison, at the same stage only 7 out of 100 people had stopped their initial treatment with levodopa.
• 33 out of 100 people who had begun treatment with dopamine agonists had uncontrolled movements.
• In comparison, 36 out of 100 people who began treatment with levodopa had uncontrolled movements.

The vast majority of participants were aged 60 or over.

The risk of side effects generally depends on the following:

• which medication is being taken
• the dose
• the person's age and whether they have other diseases
• which other medication the person is on

Dopamine agonists are generally less well tolerated than levodopa. They are more likely to cause side effects such as fluid retention (edema), sleepiness, constipation, dizziness, hallucinations and nausea. People who take dopamine agonists are therefore more likely to stop treatment or not take their medication regularly.

The possible side effects of levodopa include nausea, loss of appetite, dizziness, strong urges, depression and confusion. At high doses it can also lead to movement problems. Levodopa is usually well tolerated when taken in low doses.

Older people in particular can react to both medications with hallucinations and confusion. Parkinson's medication can also lead to impulsive, obsessive behavior such as a shopping or gambling addiction, an insatiable hunger or sexual desire, or constantly repeating aimless tasks such as putting objects into a certain order.

Because Parkinson's symptoms become worse in later stages of the disease, the dose is usually increased over time. That then causes more side effects. People with Parkinson's often take other medication to treat the side effects or other symptoms. And that increases the risk of interactions between drugs. Sometimes the side effects even outweigh the benefits of the medications. Then it can be a good idea to reduce the dose again or stop taking particular medications instead of taking more and more new ones.

After five years of treatment with medication, about 20 to 40 out of 100 people with Parkinson's notice that the drugs are becoming less effective. Their effectiveness begins to fluctuate considerably: Those affected can sometimes no longer move at all for a while, and then they can move normally again. Another possible side effect of the medication is uncontrolled (involuntary) movements. This is a sign that there's too much dopamine in some areas of the brain.

One aim of treatment is then to keep the effect of the medication as stable as possible. This may involve

• changing the times of the day when you use the medication and changing how often you use it,
• taking sustained-release tablets (which release the drug gradually),
• changing the doses and taking additional medications such as COMT inhibitors, NMDA antagonists, anticholinergic drugs or MAO-B inhibitors,
• taking a dopamine agonist in addition to levodopa.

Taking additional medication can increase your ability to move. It also decreases the likelihood of suddenly being unable to move. As mentioned above, though: the more medications you take, the more side effects can occur.

For the drug to have a stable effect, a medication pump can be used. One option is to wear a portable pump that continuously injects the drug under the skin (subcutaneously) – like an insulin pump. A second option can be considered if a feeding tube is needed due to trouble swallowing. It is inserted directly into the stomach through the abdominal wall (PEG tube). A pump can also be attached to this tube in order to deliver the drug straight into the small intestine.

Over the course of the illness, many people develop related problems such as digestive problems and dizziness, sleep problems, depression or dementia. These often require additional treatment. It then becomes even more important to look out for possible interactions between the various medications.