Dopamine metoclopramide

Metoclopramide is the drug of choice for enhancement of lactation when improved feeding technique fails to increase milk flow48 (Table 44-5). Metoclopramide exerts its effect through dopamine antagonism. Increases in milk production should be noted within 2 to 5 days of metoclopramide initiation. Monitor patients for extrapyrimidal symptoms. 

The answer is c. (Hardman, pp 932—933.) Metoclopramide antagonizes the emetic effect of apomorphine, which is mediated by a dopamine... 

Effects similar to those of the neuroleptics have also been described for other dopamine-blocking agents. Thus, parkinsonism and tardive symptoms may result from use of metoclopramide, a drug which is commonly used to enhance gastric motility, or certain antiemetics, such as perphenazine. 

Most of the antiemetic clinical trials in the last decade have involved metoclopramide (1) either as a single agent or in combination with other drugs. Similarly, most of the chemical modification studies have been designed to optimize antiemetic and/or gastroprokinetic properties of metoclopramide and to eliminate undesirable CNS side-effects which are the consequence of its dopamine D2 receptor blockade [1-3]. 

Metoclopramide, administered at doses higher than those required to inhibit apomorphine-induced emesis, was more effective than haloperidol in antagonizing cisplatin-induced emesis in dogs [80]. This was observed despite the fact that metoclopramide was considerably weaker than haloperidol as a D2-dopamine antagonist [43]. Subsequently, antiemetic efficacy of metoclopramide administered at high doses has been reported in cancer patients... 

These compounds belong to a broad class of pharmacological agents possessing D2-dopamine blocking properties which are responsible for dystonic reactions. Prochlorperazine, the most widely used phenothiazine, was more effective than placebo but did not offer advantage over the cannabinoids or butyrophenones [123], It was less effective than metoclopramide against cisplatin [81]. 

Metoclopramide may be considered as a prototype 5-HT3 antagonist because its antiemetic efficacy both in animals and man could not be adequately explained by D2-dopamine blockade. In fact, metoclopramide was considerably weaker as a D2-antagonist than haloperidol or domperidone and yet it was effective against emesis induced by anticancer agents both in animals [43, 80] and cancer patients [135]. 

Recently, several 5-HT3 antagonists have been identified and found to be effective as antiemetics in animals (Table 7.2). These compounds as a class have been proven to be free of D2-dopamine blocking properties which are responsible for dystonic side-effects seen with metoclopramide. 

The severe nausea and vomiting induced by cytotoxic drugs and radiation in man can be reduced by metoclopramide given either atone or in combination with other drugs, such as dexamethasone. However, the extrapyramidal side-effects induced by metoclopramide, due to antagonism of dopamine re-... 

Metoclopramide is a dopamine receptor antagonist, which acts selectively on the chemoreceptor trigger zone. 

We have attempted to characterize this response further and to define its pharmacology and its utility as a rapid vivo assay for octopaminergic agents, particularly for actions on the CNS (31). The response to OA is specific in that none of the other putative neuroeffectors tested induced a comparable effect with the exceptions of NE and dopamine, both of which are known to have octopaminergic actions of their own. The response to OA was blocked by typical octopaminergic antagonists such as phentolamine, metoclopramide and mianserin (Table II). 

Drugs that may interact with pergolide mesylate include dopamine antagonists, metoclopramide, and drugs known to affect protein binding. 

Metoclopramide (Region, Clopro, Octamide) [Antiemetic/ Dopamine Antagonist] Uses Tx NA Action T UGI motility, blocks dopamine in chemoreceptor trigger zone Dose Adults. 10 mg IV, 10-20 mg IM Peds. 1-2 mg/kg IV/IM Caution [B, -] Drugs w/ extrapyramidal ADRs Contra ... 

Drugs that enhance GI motility are often called prokinetics. Their goal is to increase contractile force and accelerate intraluminal transit. Most of these drugs act either by enhancing the effect of acetylcholine or by blocking the effect of an inhibitory neurotransmitter such as dopamine. The prokinetics discussed in this chapter are metoclopramide, cisapride and tegaserod, and erythromycin. 

Metoclopramide is a dopamine antagonist that centrally inhibits stimulation of the CTZ. By improving gastric emptying, it can decompress the stomach, thereby decreasing a peripherally associated stimulation of the emetic center. Metoclopramide may precipitate ex-trapyramidal reactions and sedation. For further details, see earlier section, Drugs that Increase GI Motility. 

Dopamine antagonists chlorpromazine hydrochloride metoclopramide hydrochloride perphenazine prochlorperazine prochlorperazine mesylate trifluoperazine hydrochloride... 

Metoclopramide is structurally related to orthoclopramide, a procaine derivative, and it can prolong the action of suxamethonium because of competition for cholinesterase. However, its common side effects are similar to those seen with phenothiazine derivatives. In high doses, a range of extrapyramidal symptoms may develop. The anti-emetic effects of metoclopramide are due to two main actions. Centrally, it blocks dopamine in the CTZ and peripherally, it hastens gastric emptying, abolishes irregular intestinal contractions, and increases... 

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