Apomorphine (Apokyn) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
Apomorphine is a non-selective dopamine agonist with potent D1 and D2 receptor activity, administered subcutaneously for the treatment of advanced [Parkinson's disease](/diseases/parkinsons-disease). Unlike oral dopamine agonists, apomorphine provides rapid onset of action (within 10-20 minutes), making it effective as a "rescue therapy" for sudden "off" episodes that occur despite optimized oral medication regimens.[@rascol2019] [@millan2019]
Apomorphine is unique among Parkinson's medications as the only approved injectable dopamine agonist that can be used either intermittently for rescue or continuously via infusion pump for patients with severe motor fluctuations. It was first approved by the FDA in 2004. [@pahwa2007]
Apomorphine (Apokyn) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
Apomorphine is a non-selective dopamine agonist with potent D1 and D2 receptor activity, administered subcutaneously for the treatment of advanced [Parkinson's disease](/diseases/parkinsons-disease). Unlike oral dopamine agonists, apomorphine provides rapid onset of action (within 10-20 minutes), making it effective as a "rescue therapy" for sudden "off" episodes that occur despite optimized oral medication regimens.[@rascol2019] [@millan2019]
Apomorphine is unique among Parkinson's medications as the only approved injectable dopamine agonist that can be used either intermittently for rescue or continuously via infusion pump for patients with severe motor fluctuations. It was first approved by the FDA in 2004. [@pahwa2007]
Mechanism of Action
Dopamine Receptor Activation
Apomorphine acts as a direct agonist at both D1-like (D1, D5) and D2-like (D2, D3, D4) dopamine receptors:[@millan2019] [@katzenschlager2018]
D1 receptor activation: Mimics dopamine's effects on motor control through direct stimulation
D2 receptor activation: Provides anti-parkinsonian effects similar to other agonists
Apomorphine has affinity for: [@olanow2022]
D1: Ki = 2.2 nM (high affinity)
D2: Ki = 0.4 nM (very high affinity)
D3: Ki = 0.07 nM (highest affinity)
D4: Ki = 4.6 nM
Pharmacokinetics
Onset: 10-20 minutes after subcutaneous injection
Peak effect: 20-40 minutes post-injection
Duration: 60-90 minutes per dose
Half-life: 30-60 minutes
Bioavailability: Approximately 100% subcutaneously
Clinical Applications
Intermittent Injection (Rescue Therapy)
Apomorphine injection is indicated for acute rescue from "off" episodes:[@pahwa2007]
Rapid reversal of severe akinesia or freezing
Treatment of sudden motor fluctuations not controlled by oral medications
Emergency use when oral therapy impossible (e.g., pre-operative fasting)
Dosing: Starting dose 0.2 mL (2 mg), titrated in 0.1 mL increments to optimal response. Maximum single dose 0.6 mL (6 mg). Typically 3-4 injections daily.
Continuous Infusion (Apomorphine Pump)
For patients with severe motor fluctuations, continuous subcutaneous infusion provides:[@katzenschlager2018]
More stable plasma drug levels
Reduced "off" time by up to 50%
Improved "on" time without troublesome dyskinesias
[Parkinson's Foundation - Apomorphine](https://www.parkinson.org/Living-with-Parkinsons/Treatment/Medication/Apomorphine)
Background
The study of Apomorphine (Apokyn) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Allen Brain Atlas Resources
[Allen Brain Atlas - Gene Expression](https://human.brain-map.org/) - Search for gene expression data across brain regions
[Allen Brain Atlas - Aging, Dementia & TBI](https://aging.brain-map.org/) - Data on aging and traumatic brain injury
References
[Rascol O, et al, Subcutaneous apomorphine in Parkinson's disease (2019)](https://pubmed.ncbi.nlm.nih.gov/31126584/)
[Millan MJ, et al, Dopamine receptor agonists: from new structures to new clinical applications (2019)](https://doi.org/10.1016/j.pharmthera.2019.02.001)
[Pahwa R, et al, Apomorphine in Parkinson disease: evidence-based review (2007)](https://pubmed.ncbi.nlm.nih.gov/17626569/)
[Katzenschlager R, et al, Apomorphine infusion in advanced Parkinson's disease: a systematic review (2018)](https://pubmed.ncbi.nlm.nih.gov/29486279/)
[Olanow CW, et al, Apomorphine: past, present, and future (2022)](https://pubmed.ncbi.nlm.nih.gov/35671234/)
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