Ondansetron Apomorphine

Apomorphine is approved for acute off episodes in patients with advanced stages of PD. The onset of effect is within 10 to 20 minutes and the duration of effect is about 60 minutes. It requires premedication with an antiemetic because it causes nausea and vomiting. Antiemetics that block central dopamine worsen the symptoms of PD, and 5-HT3 antagonists, such as ondansetron, can aggravate PD-related hypotension. Trimethobenzamide (300 mg three times daily) should be... 

Apomorphine is a nonergot dopamine agonist given as a subcutaneous rescue injection. For patients with advanced PD with intermittent off episodes despite optimized therapy, subcutaneous apomorphine triggers an on response within 20 minutes, and duration of effect is up to 100 minutes. Most patients require 0.06 mg/kg. Prior to injection, patients should be premedicated with the antiemetic trimethobenzamide. It is contraindicated with the serotonin-3-receptor blockers (e.g., ondansetron). 

Hypersensitivity to the drug or any components of the product concomitant use of apomorphine with drugs of the 5HT3 antagonist class (eg, ondansetron,... 

B. Two medicines, ipecac and apomorphine, induce vomiting. Metoclopramide is a prokinetic with antiemetic properties and therefore would have the opposite of the desired effect. Morphine is an opioid with analgesic and sedating properties. Promethazine and ondansetron are also antiemetics, not emetics. 

Ondansetron also produced a dose-dependent blockade of conditioned taste aversion induced by apomorphine [McAllister and Pratt 1998). 

The hypotensive adverse effects of apomorphine may possibly be increased by alcohol. The concurrent use of other drugs used for erectile dysfunction or dopamine agonists or antagonists is not recommended. However, domperidone, and prochlorperazine are said not to interact when apomorphine is used for erectile dysfunction, and domperidone is the recommended antiemetic when apomorphine is used for Parkinson s disease. There is evidence that antidepressants, antiepileptics, and ondansetron do not interact adversely. 

The small doses of apomorphine used for erectile dysfunction (2 to 3 mg) do not normally cause vomiting, but nausea does occur in about 7% of patients and the manufacturers say that interaction studies and/or clinical experience show that domperidone, ondansetron or prochlorperazine may safely be given as antiemetics in this patient group. Studies with other antiemetics have not been carried out, so at the moment concurrent use is not recommended. ... 

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. 

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