Terms to Describe Wearing Off
'On-time' is the time when a Parkinson’s disease (PD) patient finds that their levodopa medication is having benefit, and their Parkinson’s symptoms are generally well controlled.
'Off-time' is when a PD patient’s levodopa medication is no longer working well for them, and their Parkinson’s symptoms have returned. The return of PD symptoms may include e.g.; slowness, stiffness or tremor; and sometimes total (akinesia) or partial (bradykinesia) immobility.
Wearing off is where people with PD begin to feel that the improvement gained from a dose of levodopa medication gradually fades off and does not last until the time that the next dose of levodopa is due or begins to work (this feeling has often been likened to a car gradually running outr of petrol). As a PD patient, you may therefore feel that you need your next dose of levodopa sooner.
Delayed 'on' is when there is an increased delay between taking levodopa medication and before the benefits are felt by a PD patient. This may be more common with controlled-release preparations of levodopa, as they can take some time to dissolve in the stomach, enter the blood stream and travel into the brain in sufficient quantities to replace the missing dopamine.
The on-off phenomenon refers to sudden, sometimes unpredictable changes in a PD patient's symptoms, varying between mobility (usually with dyskinesia) and immobility due to the return of Parkinson’s symptoms. These sudden fluctuations can have no apparent relationship to medication timing.
Freezing episodes are sudden, brief (seconds to minutes) periods of immobility where a PD patient may find their feet 'stuck to the spot', as if they are glued to the floor. Freezing most often occurs when trying to initiate walking, whilst turning in confined spaces, or when going through doorways.