Levodopa Domperidone

With most DA agonists there are the other expected signs of increased DA activity such as hallucinations, psychosis and hypotension which can be worse than with levodopa. Fortunately vomiting can be countered by giving the DA antagonist domperidone. This does not cross the blood-brain barrier and so counteracts only the peripheral (chemoreceptor trigger zone) effect of the DA agonist (Fig. 15.5). 

Note that prochlorperazine should not be given if apomorphine is used for Parkinson s disease, as its dopamine antagonist actions can worsen the disease (see also Levodopa + Antiemetics , p.682). Because apomorphine is highly emetogenic at the doses required for the treatment of Parkinson s disease (1 to 4 mg/hour by subcutaneous infusion), patients with Parkinson s disease requiring apomorphine should be pretreated with domperidone 20 mg three times daily for at least 2 days. Rare reports of extrapyramidal adverse effects have been reported with ondansetron, which may be of relevance in patients with Parkinson s Disease. 

Josamycin. An elderly man with Parkinson s disease, well-controlled for 10 months with daily levodopa/benserazide, bromocriptine 70 mg and domperidone, was additionally given josamycin 2 g daily for a respiratory infection. Shortly after the first dose he became drowsy with visual hallucinations, and began to show involuntary movements of his limbs, similar... 

Domperidone is a dopamine antagonist similar to metoclopramide. However, since it acts on the dopamine receptors in the stomach wall, and unlike metoclopramide, it does not readily cross the blood-brain barrier, it does not appear to oppose the effects of levodopa within the brain, although some extrapyramidal symptoms have been observed. It may even slightly increase the bioavailability and effects of levodopa (by stimulating gastric emptying). Domperidone can therefore be used to control the nausea and vomiting associated with levodopa treatment of Parkinson s disease. 

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