Metoclopramide (Plasil): Dosage, Mechanisms, and Clinical Use

Route	Indication	Adults	Pediatrics
Intravenous (IV)	Nausea and Vomiting	10 mg IV, administered slowly over 1-2 minutes, up to three times a day if needed	0.1 to 0.15 mg/kg per dose, up to three times a day
	Gastroparesis	10 mg IV, administered slowly over 1-2 minutes, 3 to 4 times daily before meals and at bedtime	0.1 to 0.15 mg/kg per dose, up to three times a day
Oral (PO)	Nausea and Vomiting	10-15 mg taken 30 minutes before meals and at bedtime, up to four times a day	0.1 to 0.15 mg/kg per dose, up to three times a day
	Gastroparesis	10 mg taken 30 minutes before meals and at bedtime, up to four times a day	0.1 to 0.15 mg/kg per dose, up to three times a day

Important Notes:

• Duration of Use: The use of metoclopramide should generally be limited to 12 weeks to reduce the risk of tardive dyskinesia, a potentially irreversible condition.

• Adjustments: Dose adjustments may be necessary for patients with renal or hepatic impairment.
  

The dosage of metoclopramide (Plasil) varies depending on the indication and the route of administration. Here are the common dosages:

Intravenous (IV):

• Adults:

• Nausea and Vomiting: 10 mg IV, administered slowly over 1-2 minutes, up to three times a day if needed.

• Gastroparesis: 10 mg IV, administered slowly over 1-2 minutes, 3 to 4 times daily before meals and at bedtime.

Oral (PO):

• Adults:

• Nausea and Vomiting: 10-15 mg taken 30 minutes before meals and at bedtime, up to four times a day.

• Gastroparesis: 10 mg taken 30 minutes before meals and at bedtime, up to four times a day.
  

Pediatric Dosage:

• IV and PO:

• Typically, the dosage for children is 0.1 to 0.15 mg/kg per dose, given up to three times a day.
  

Important Notes:

• Duration of Use: The use of metoclopramide should generally be limited to 12 weeks to reduce the risk of tardive dyskinesia, a potentially irreversible condition.

• Adjustments: Dose adjustments may be necessary in patients with renal or hepatic impairment.

As with any medication, it is essential to follow the prescribing physician's recommendations and to adjust the dosage based on the specific clinical scenario and patient response.

Mechanisms of Action

Plasil, known generically as metoclopramide, works through several mechanisms of action:

1. Dopamine D2 Receptor Antagonism: Metoclopramide blocks dopamine receptors in the chemoreceptor trigger zone (CTZ) of the brain, which helps reduce nausea and vomiting.

2. Serotonin Receptor Modulation: At higher doses, it can also block serotonin receptors (5-HT3) in the CTZ and the gastrointestinal tract, further aiding in antiemetic effects.

3. Prokinetic Action: It enhances gastrointestinal motility by increasing the amplitude of gastric contractions, relaxing the pyloric sphincter, and promoting coordinated peristalsis, which helps in gastric emptying and reduces symptoms of gastroparesis.
   

Reason for Administration with Tramadol

Tramadol is an opioid analgesic that can cause nausea and vomiting as common side effects. By co-administering metoclopramide (Plasil), the antiemetic and prokinetic properties help to mitigate these gastrointestinal side effects, making tramadol more tolerable for patients. This combination can enhance patient comfort and compliance with pain management regimens.

Major Pitfalls to Consider

1. Masking of Symptoms: In neurosurgical patients, metoclopramide can mask symptoms of increased intracranial pressure (ICP), such as nausea and vomiting, which are critical for monitoring neurological status.

2. Risk of Tardive Dyskinesia: Long-term use can lead to tardive dyskinesia, an often irreversible condition characterized by involuntary movements, especially in elderly patients.

3. Extrapyramidal Symptoms (EPS): Metoclopramide can cause EPS, including acute dystonic reactions, akathisia, and parkinsonism, especially in young adults and pediatric patients.

4. Neuroleptic Malignant Syndrome (NMS): Rare but potentially fatal, characterized by hyperthermia, altered mental status, muscle rigidity, and autonomic dysfunction.

5. Contraindications: Avoid in patients with a history of bowel obstruction, perforation, or hemorrhage, and in those with pheochromocytoma due to the risk of hypertensive crises.

6. Interactions with CNS Depressants: Use caution when co-administering with other CNS depressants as it may potentiate sedative effects.

7. Prolonged QT Interval: Metoclopramide can prolong the QT interval, increasing the risk of arrhythmias, especially in patients with underlying heart conditions.