DRUGS ACTING ON GASTROINTESTINAL SYSTEM

THE ANTI-EMETIC

Antiemetic classification

• Neuroleptic: Chlorpromazine, Haloperidol
• Prokinetic drugs: Metoclopramide, Domperidone.
• 5 - H*T {3} antagonists: Granisetron and Ondansetron
• Anticholinergics: Hyoscine, Dicyclomine
• H {1} antihistaminics: Cyclizine, Promethazine

PROMETHAZINE

Promethazine relieves the nausea and vomiting brought on by an excess of histamine, which is typically seen in allergic conditions.

Mechanism of action

It has an antiemetic effect by acting as an inhibitor on the chemoreceptor trigger zone in the medulla. Additionally, it has anticholinergic properties that depress the CNS.

Indication

• Motion sickness
• Early morning sickness
• Preoperative sedation.
• Postoperative vomiting

Postoperative vomiting

Adults who experience Postoperative Vomiting should take 25 mg 30–60 mins prior to departure; they may repeat it in 8–12 hrs; and they should take 25 mg twice daily as maintenance.

Preoperative nausea and vomiting: 25 mg; additional doses of 12.5–25 mg may be given every 4-6 hours.

Contraindication

Children under 2 years old, Reye's syndrome, encephalopathy, hepatic diseases, epilepsy, bone marrow depression, stenosing peptic ulcer, pyloroduodenal obstruction, prostatic hypertrophy, bladder neck obstruction, lactation, newborn or premature infants, acutely ill or dehydrated children

Side Effects

Uncertainty, disorientation, torticollis, euphoria, diplopia, tachycardia, bradycardia, leukopenia, thrombocytopenia, agranulocytosis, dry mouth, and neuroleptic malignant syndrome

Nursing Considerations

• A full glass of water or milk should be consumed with the oral dose to reduce GI distress.
• Large muscle mass should receive an IM injection. 
• Rotate injection sites and monitor them on a daily basis.
• 25mg of an IV injection per minute is recommended.
• Because subcutaneous injection can cause chemical irritation and necrosis, it should not be used.
• Regularly check the patient's blood pressure, pulse, and rate of respiration.
• Keep an eye out for any extrapyramidal side effects in the patient. Notify a doctor if these symptoms develop.
• Keep an eye out for neuroleptic malignant syndrome (NMS). Notify a doctor immediately if any of these symptoms occur.
• Evaluate the level of sedation administered. When used in conjunction with other medications that depress the central nervous system, there is an increased risk of sedation and respiratory depression.
• Promethazine can make you sleepy and slow down your central nervous system (CNS). It can also affect your physical and mental abilities, so patients should be careful about doing things that require mental alertness (ie, operating machinery or driving).

METOCLOPRAMIDE

It blocks central dopamine receptors very well.

Action mechanism

The antiemetic effect comes from the fact that the drug raises the Chemoreceptor trigger zone (CTZ) threshold and makes the stomach empty faster.
It increases the tone of the lower esophageal sphincter, relaxes the pyloric antrum and duodenal cap, and speeds up the emptying of the upper gut and increases peristalsis.

Indication

Vomiting, nausea
Gastroesophageal Reflux (GERD)
Diabetic Gastroparesis
Diabetic Gastroparesis
Emesis Induced By Chemotherapy

Dose

• Adult: 10 mg once daily;
• Child: 0.25 mg/kg given in divided Adult: 10 mg once daily;

Contraindication

History of Gl obstruction, a history of seizures, and pheochromocytoma

Side Effects:

Side effects include amenorrhea, methemoglobinemia, loose stools, drowsiness, anxiety, agitation, depression, and galactorrhea in females and gynecomastia in males. 

Nursing consideration:

• The oral dose should be administered at bedtime and 30 minutes before meals.
• Extrapyramidal symptoms (parkinsonian: difficulty speaking or swallowing, loss of balance control, pill rolling, mask-like face, shuffling gait, rigidity, tremors, and dystonic muscle spasms, weakness of arms or legs) are most likely to manifest in children, young adults, and older adults and are associated with high-dose therapy. If extrapyramidal reaction symptoms develop, stop therapy and let your doctor know.
• Keep an eye out for tardive (uncontrolled rhythmic mouth, face, and extremity movement, lip dyskinesia smacking or puckering, puffing of cheeks, and uncontrolled chewing), and alert the doctor if the patient exhibits any of these symptoms.
• Keep an eye out for the symptoms of neuroleptic malignant syndrome (hyperthermia, rigidity in the muscles, altered consciousness, irregular heartbeat or blood pressure, tachycardia, and diaphoresis), and contact the doctor if you notice them.
• Keep an eye out for any signs of hypernatremia and hypokalemia, especially if the patient has cirrhosis or CHF.
• Large muscle mass should get an IM injection. daily observation and site rotation for injections.
• Give the direct IV dose slowly over 1 to 2 minutes. A brief but intense feeling of anxiety and restlessness is brought on by rapid administration, which is quickly followed by sleepiness.
• During therapy, refrain from driving and other potentially risky activities. Without first consulting a doctor, avoid breastfeeding while taking this medication.

DOMPERIDONE

Domperidone is a type 2 peripheral dopamine receptor blocker. It is chemically similar to haloperidol, but it works in the same way as metoclopramide.

Mechanism of action

It reduces nausea by blocking receptors at the chemoreceptor trigger zone (CTZ) at the floor of the fourth ventricle and functions as a peripherally selective antagonist of the dopamine D2 and D3 receptors.

Indication

• Vomiting, nausea, and the management of gastroesophageal reflux disease.
• Vomiting brought on by chemotherapy

Dose

Adult: 10 mg once daily (up to 30 mg).

Contraindication

mechanical illness, hemorrhage in the intestines. Hirschsprung's , obstruction or perforation

Side Effects

unstable stools Heart arrhythmia, gynecomastia, and headache (on rapid IV injection). diarrhea, dry mouth, and dystonic response.