Drugs Affecting GIT Motility

CHAPTER 5

DRUGS AFFECTING GIT MOTILITY

 

• Gastrointestinal tract shows various movements from the esophagus to the rectum for the purpose of mixing the food with gastric enzymes in the stomach, movement of food from the mouth towards rectum etc.
• The gastrointestinal tract consists of smooth muscle which is involuntary (not under our control).
• The condition or disorder related to gastrointestinal movement is vomiting and
• The drugs acting on the movement of the GIT can be either emetic (drugs producing vomiting) or antiemetic (drugs preventing vomiting).
• The drugs acting on the movement of GIT can also be laxative/purgatives (drugs increasing peristalsis) or anti-diarrheal (drugs preventing diarrhoea).
• Usually after any abdominal operation, as a sudden effect, the GIT peristalsis stops for a few days and hence nothing should be given from mouth as long as the motility does not start. Hence the treating doctor writes on the patient case sheet as “NPO” (Nill Per). But there may be a situation where the GIT peristalsis does not start even after a few days and this condition is called paralytic ileus. In these drugs like cholinergic (which increases GIT increases smooth muscle contraction) are used.
• Sometimes the condition may lead to spasm of GIT smooth muscle leading to abdominal pain. In these conditions, anticholinergics/antispasmodics (drugs causing smooth muscle relaxation of GIT which relieves spasm) are used.

 CHAPTER 5.1

EMETICS AND ANTIEMETICS

VOMITING

It is a protective reflex with reverse peristalsis in order to expel the gastric contents through the enteral route. Severe vomiting may lead to dehydration and electrolyte imbalance.

COMMON CAUSES OF VOMITING

• Unpleasant sight & smell induces nausea and vomiting
• Motion sickness induces nausea and vomiting
• GIT causes: Gastritis, GERD, Foreign bodies, toxin etc induces nausea and vomiting
• Chemotherapy, radiotherapy or pregnancy induces nausea and vomiting

PATHOPHYSIOLOGY OF VOMITING 

There are main four sources through which the vomiting centre can get stimulated resulting in vomiting:

The chemoreceptor trigger zone (CTZ) is located in the fourth ventricle in the area postrema of the brain. This is outside the blood-brain barrier (BBB).  The emetogenic stimuli in the blood or cerebrospinal fluid can stimulate this which inturn stimulate vomiting centre. The chemoreceptor trigger has dopamine (D2 receptors), Histamine receptor (H1), serotonin (5-HT3 receptors), muscarinic receptors (M1/M3), and cannabinoid receptors. 

(Remember the receptors in CTZ as D2, H1, 5-HT3, M1/M3 and cannabinoid receptors)

The vestibular apparatus in the middle ear is important in motion sickness (travelling sickness) via cranial nerve VIII. It has histamine (H1 receptors) and muscarinic receptors (M1/M3). 

(Remember the receptors in vestibular apparatus as H1 and M1/M3)

Irritation of the pharynx, innervated by the vagus nerve or irritation of enteric afferent nerves in the mucosa of the gastrointestinal tract by chemotherapy, radiation therapy, distention, or acute infectious gastroenteritis leads to release of mucosal serotonin and activation of serotonin receptors (5HT3) or dopamine receptor (D2) which stimulate vagal nerve which stimulates chemoreceptor trigger zone and directly vomiting centre. 

(Remember the receptors in pharynx and GIT as 5HT3 and D2)

The central nervous system plays a role in vomiting due to psychiatric disorders, stress, and

Or due to abnormal smell, sight etc leading to anticipatory vomiting.

 

 

Table

Receptors in chemoreceptor trigger zone (CTZ)	Receptors in vestibular apparatus	Receptors in pharynx and GIT
D2, H1, 5-HT3, M1/M3 and cannabinoid receptors	H1 and M1/M3	5HT3 and D2

 EMETICS

Emetics are the agents are used for deliberate (purposeful) production of emesis for treatment of toxin or for aversion therapy towards addicting drugs.

CLASSIFICATION OF EMETICS

Centrally acting: Emetine, Dihydro emetine and Apomorphine

Peripherally acting: Ipecacuanha

Centrally & Peripherally: Sodium chloride solution, Mustard powder and Antimony Potassium tartrate.

CENTRALLY ACTING EMETICS

• Emetine
• Dihydro Emetine

(MESSAGE TO STUDENTS: I don’t think you need the formula to remember centrally acting emetics as the name itself tells the name of the drugs, so instead of emetics, remember the drug name as Emetine and just add Dihydro to emetine and remember the second drug. ok

• Emetine, an alkaloid derived from ipecac, and dehydroemetine, a synthetic analogue of emetine
• Apomorphine is an opiate drug

MECHANISM OF ACTION

• Emetine, dehydroemetine and apomorphine are centrally acting emetics which act as a potent central dopamine agonist to directly stimulate the CTZ which in turn stimulate vomiting centre causing vomiting. 

USES

• Previously emetines were used to induce vomiting in order to remove ingested toxin but nowadays are not used for such purpose due to toxicity.

However, Emetine and dehydroemetine has anti-protozoal properties and hence used in amoebiasis (See chapt for details)

PERIPHERALLY ACTING EMETICS

Ipecacuanha

• Ipecacuanha is a common name native to brazil obtained from “Carapichea ipecacuanha” which is a species of flowering plant belonging to Rubiaceae family.

• The roots or its powder were used to make a syrup of ipecac, as a powerful emetic.

MECHANISM OF ACTION

The peripheral-acting emetics directly stimulate the pharynx, which triggers the emetic centre through stimulation of the ninth cranial nerve, or the visceral afferent nerves of the stomach and intestines by causing irritation, inflammation, or distention. 

USES

Ipecacuanha has a long history of use as an emetic, for emptying the stomach in cases of the toxin.

The most common and familiar preparation is a syrup of ipecac, which was commonly recommended as an emergency treatment for accidental toxin until the 20th century. But now it is not used for such purposes.

CENTRALLY & PERIPHERALLY EMETICS

Sodium chloride (NaCl)

• Sodium chloride (NaCl), also known as salt, common salt or table salt which we use in the kitchen in our daily life
• When dissolved in water, the sodium chloride framework disintegrates as the Na+ and Cl− ions become surrounded by the polar water molecules.

MECHANISM OF ACTION

It is known to act both by central and peripheral mechanisms

USES

Previously it was used as saline emetics commonly to induce vomiting in case of suspected toxin or in order to clean stomach. But now it is not advised because of the danger of fatal hypernatremia, cerebral damage such as seizures, fever and somnolence.

 

Mustard powder

Mustard is obtained from plant species Brassica nigra which we use in the kitchen in our daily life

MECHANISM OF ACTION

It is known to act both by central and peripheral mechanisms

USES

One to three tablespoons of powdered mustard dissolved in a glass of warm water is a homemade emetic for the purpose of inducing mild emesis in case of stomach upset. Nevertheless, never try at home without the supervision of an expert.

ANTIMONY POTASSIUM TARTRATE

• Antimony potassium tartrate, also known as potassium antimonyl tartrate or emetic tartar.

• Antimony potassium tartrate's potential as an emetic was known since the Middle Ages. The compound itself was considered toxic and therefore a different way to administer it was found. Cups made from pure antimony were used to store wine for 24 hours and then the resulting solution of antimony potassium tartrate in wine was consumed in small portions until the wanted emetic effect was reached.

MECHANISM OF ACTION

It is known to act both by central and peripheral mechanisms

USES

It is not used as emetics in humans nowadays, but as genetics, it is used only for veterinary purpose.

CHAPTER 5.2

ANTIEMETICS

Antiemetics are the drugs used to prevent vomiting due to any cause.

CLASSIFICATION OF ANTIEMETICS

Serotonin Antagonists - drugs that block 5 HT₃ receptors

Anticholinergics- drugs that block M₁/M₃receptors

Dopamine Antagonist -drugs that block D₂ receptors

Neuroleptics / Antipsychotics - also the drugs that block D₂ receptors

Antihistaminics -drugs that block H₁ receptors

Adjuvant antiemetics: Cannabinoids, Benzodiazepines (BZDs) and Corticosteroids

(MESSAGE TO STUDENTS: Remember the formula for antiemetics as “SAD-NAA”, so it becomes Serotonin Antagonists, Anticholinergics, Dopamine Antagonist, Neuroleptics / Antipsychotics, Antihistaminics and Adjuvant antiemetics).

5-HT₃ ANTAGONIST / SEROTONIN ANTAGONISTS

Drugs used:    Granisetron                                 

                      Ondasetron (Prototype)    

                      Dolasetron

(MESSAGE TO STUDENTS: Formula to remember the Serotonin antagonist is “GOD”. Here all the names of the drug end with “Setron” and you should remember Grani, Onda and Dola, which will become Grani-setron, Onda-setron and Dola-setron).

MECHANISM OF ACTION

• These are the drugs that block 5 HT₃ receptors in the vomiting centre & chemoreceptor trigger zone (CTZ)
• They also block 5 HT₃ receptors stimulation in GIT and pharynx (Prominent action).

USES

Chemotherapy-induced nausea & vomiting – given 30 min. before chemotherapy.

To prevent postoperative & postradiation nausea & vomiting

DOSE AND ROUTE OF ADMINISTRATION

Granisetron    10 mg / kg / day also can be given as i.v

Ondansetron 32 mg / day

Dolasetron       1.8 mg / kg / day i.v

ADVERSE EFFECTS

Headache & mild constipation or diarrhea is common

All three drugs cause prolongation of QT interval, but more pronounced with dolasetron – the chance of arrhythmias.

DRUG INTERACTIONS

Concomitant 5HT antagonist + apomorphine

CONTRAINDICATIONS

The patient suffering from arrhythmia

ANTICHOLINERGICS

Drugs used:   Hyoscine (scopolamine)

MECHANISM OF ACTION

M₁/M₃receptors in the vestibular apparatus gets stimulated during long travel or if somebody travels to the hill at high altitude

Hyoscine (scopolamine) is an anticholinergic drug that blocks M₁/M₃receptors in the vestibular apparatus, hence prevents the stimulation of vomiting centre

USES

Motion sickness

DOSE AND ROUTE OF ADMINISTRATION

Used as a transdermal patch

ADVERSE EFFECTS

Dry mouth, blurred vision, feeling dizzy and sleepiness

 

DOPAMINE ANTAGONIST

Drugs used:    Metoclopramide   

                          Domperidone       

(MESSAGE TO STUDENTS: Formula to remember Dopamine Antagonist is “MD”, you can remember as “Managing Director”, which becomes  Metoclopramide and   Domperidone. Just split the names of the word and remember as Meto-clo-pra-mide and Dom-peri-done.       

MECHANISM OF ACTION

• These drugs block D₂ receptors in the chemoreceptor trigger zone (CTZ) and gastrointestinal tract (GIT), thus inhibiting stimulation of vomiting centre.
• Both these drugs also have 5HT₄ agonist activity in GIT – Increases downward peristalsis of GIT hence they are also called as prokinetic agents. 

USES

• Nausea and vomiting
• Chemotherapy-Induced Nausea and Vomiting

DOSE AND ROUTE OF ADMINISTRATION

Metoclopramide    2.5 mg bid (can also be given intravenous or intramuscular)

Domperidone     10 mg bid 

In severe nausea and vomiting, even parenteral Metoclopramide can be prefered

ADVERSE EFFECTS

Metoclopramide crosses BBB and can cause blockage of D2 receptor in substantia nigra (Basal ganglia) in CNS leading to extrapyramidal side effects (symptoms like parkinsonism- also termed as drug-induced parkinsonism).

Domperidone does not crosses BBB and hence no extrapyramidal side effects but it may cause Disorientation, Dizziness, Fainting, Light-headedness etc

DRUG INTERACTION

• Metoclopramide + Antipsychotics: increased risk of extrapyramidal symptoms
• Metoclopramide + central nervous system depressants: Increased sedation
• Domperidone + Co-administration of ketoconazole, erythromycin, or other potent CYP3A4 inhibitors which prolong the QTc interval such as fluconazole, voriconazole, clarithromycin, amiodarone, and telithromycin may cause arrhythmia.

CONTRAINDICATION

Metoclopramide: Breastfeeding and Gastrointestinal obstruction, perforation or haemorrhage

Domperidone: Known hypersensitivity to domperidone or any of the excipients and Prolactin-releasing pituitary tumour and moderate or severe hepatic impairment

NEUROLEPTICS / ANTIPSYCHOTICS

Drugs used: Phenothiazines: Prochlorperazine

                       Butyrophenones: Droperidol

(MESSAGE TO STUDENTS: Formula to remember Neuroleptics / Antipsychotics is “PPBD”, you can remember as “Please Protect Bus Driver”, which becomes Pheno-thia-zines considering the drug Pro-clor-pera-zine and Butyro-phenones considering the drug Dro-peri-dol

MECHANISM OF ACTION

• These drugs block D₂ receptors in CTZ and prevent the stimulation of vomiting centre.
• These drugs also block D₂ receptors in substantia nigra (Basal ganglia) and decrease the overaction of excess of dopamine, hence are used as Neuroleptic effect / Antipsychotic drugs 

USES

Prochlorperazine and Promethazine is used to treat Vertigo with nausea and vomiting

Droperidol is used to prevent postoperative nausea & vomiting

ADVERSE EFFECTS:

Cause QT prolongation may lead to arrhythmia

DOSE AND ROUTE OF ADMINISTRATION

Prochlorperazine 5, 10, mg tablets; 5 mg/5 mL syrup

Droperidol : Parenteral: 2.5 mg/mL for IV or IM injection

ADVERSE EFFECTS

• Sedation
• Headaches
• Dizziness
• Diarrhoea
• Anxiety

DRUG INTERACTION

Neuroleptics / Antipsychotics + sedatives, anticholinergics, antihistaminics leads to additive effects

CONTRAINDICATION

Pregnancy and lactation

ANTIHISTAMINICS

Drugs used

• Promethazine
• Cyclizine
• Meclizine

(MESSAGE TO STUDENTS: Formula to remember antihistaminics as antiemetics is “PCM”, you can remember as “Physics, Chemistry, Mathematics”, which becomes Promethazine, Cyclizine and Meclizine. The name of all the drugs ends with the word “Zine”, you have to remember Prometha, Cycli and  Mecli, which becomes Prometha-zine, Cycli-zine and Meclizine.

MECHANISM OF ACTION

These drugs block H₁ receptors in CTZ and vestibular apparatus and prevent the stimulation of vomiting centre.

USES

Motion sickness/ travel sickness,

Morning sickness in pregnancy, and to combat opioid-induced nausea.

ADVERSE EFFECTS

Sedation and drowsiness (due to blockade of  H₁ receptors in the hypothalamus)

DOSE AND ROUTE OF ADMINISTRATION

25–50 mg

DRUG INTERACTION

Diazepam + Antihistaminic leads to the increased sedative effect

Alcohol + Antihistaminic leads to the increased sedative effect

CONTRAINDICATION

During pregnancy and lactation -can harm the development of the fetus.

In children under the age of 12 years.

ADJUVANT ANTIEMETICS

Drugs used: Cannabinoids, Benzodiazepines and Corticosteroids: These drugs have additional antiemetic action.

CHAPTER 5.3

LAXATIVE / PURGATIVES AND ANTIDIARRHEALS

The system of GIT is designed in such a way that if we eat proper fibre-containing food and consume fluid (water) adequately then there will be the proper formation of stool / faecal matter.

CONSTIPATION

There are many conditions where stool / faecal matter are not properly formed with passage of unformed and hard stool. This condition is called “Constipation”. Constipation may be acute (short term) or chronic (present from long term).

CAUSES FOR CONSTIPATION

• Improper food habit with less fibre and inadequate fluid(water) consumption
• Effect of some disease
• Due to side / adverse effect of some drugs
• Drugs used to treat acute or chronic constipation are Laxatives and Purgatives

LAXATIVE / PURGATIVES

Drugs used to treat constipation (acute or chronic), are called as laxatives or purgatives. Sometimes laxatives are used preoperatively (one day (8hrs) before operation) for the purpose of clearing the content of GIT even though the patient is not suffering from constipation.

LAXATIVES (APERIENTS)

• The English word "laxative" comes from Old French laxative, which came from the Latin laxatus. The Latin word Laxare means "to loosen", while the Latin word Laxus means "loose, lax".
• Laxatives are drugs that facilitate or increase bowel movements.

PURGATIVES

Pergatives tends to cleanse or purge, especially causing the evacuation of the bowels. Purgatives have a more powerful effect than laxatives.

LAXATIVES (BOSS-A)

• Bulk-forming Laxatives
• Osmotic Laxatives
• Stimulant Laxatives
• Stool Surfactant Agents (Stool Softeners)
• Anthraquinone Derivatives

PURGATIVES (MS)

• Magnesium citrate
• Sodium phosphate.

Now let us study each under the following format, ok…

LAXATIVES

1. BULK-FORMING LAXATIVES

DRUGS USED: Plant products like Psyllium, Methylcellulose and synthetic fibres like Polycarbophil.

MODE OF ACTION: Bulk-forming laxatives are indigestible and hydrophilic colloids which absorb water from surrounding in the lumen of the large intestine, forming a bulky and emollient gel that distends the colon and promotes peristalsis.

DOSE AND ROUTE OF ADMINISTRATION

• Psyllium granules or powder per packet.
• Methylcellulose: bulk powder
• Polycarbophil: 500, 625 mg tablets; 500 mg chewable tablets

USES: Acute and Mild constipation

ADVERSE EFFECT: Bacterial digestion of plant fibres within the colon may lead to increased bloating and flatus.

DRUG INTERACTION

This laxative may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS

Undiagnosed intestinal obstruction and paralytic ileus

2. OSMOTIC LAXATIVES

DRUGS USED:

• Non-absorbable Salts like Magnesium Hydroxide (Milk of Magnesia)
• Non-absorbable sugars like Sorbitol and Lactulose
• Balanced Polyethylene Glycol (PEG)

MODE OF ACTION:

Osmotic laxatives are soluble but non-absorbable compounds that result in increased stool liquidity due to an obligate increase in faecal fluid.

USES: Chronic constipation

DOSE AND ROUTE OF ADMINISTRATION

• Magnesium hydroxide (milk of magnesia) : 400, 800 mg/5 mL aqueous suspension
• Sorbitol : Children >12 years and Adults: : 30-150 mL (as 70% solution) and Rectal enema: 120 mL as 25% to 30% solution
• Lactulose : 15-30 mL/day increased to 60 mL/day in 1-2 divided doses if necessary.

ADVERSE EFFECT:

• Magnesium hydroxide should not be used for prolonged periods in patients with renal insufficiency due to risk of hypermagnesemia.
• Sorbitol and Lactulose sugars are metabolized by colonic bacteria, producing severe flatus and cramps.

DRUG INTERACTION

This laxative may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS

Undiagnosed intestinal obstruction and paralytic ileus

BALANCED POLYETHYLENE GLYCOL

Polyethylene glycol (PEG) (it is an isotonic solution contain contains combination of an inert, nonabsorbable, osmotically active sugar (PEG) with sodium sulfate, sodium chloride, sodium bicarbonate, and potassium chloride. It is an osmotic laxative.

ADVANTAGE OF THIS COMBINATION: The solution is formulated in such a way that no significant intravascular fluid or electrolyte shifts occur.

DOSE AND ROUTE OF ADMINISTRATION

The solution should be ingested rapidly (4 Litre over 2 hours) to promote bowel cleansing.

USES: Used for complete colonic cleansing prior to gastrointestinal endoscopic procedures.

For treatment or prevention of chronic constipation, smaller doses of PEG powder may be mixed with water or juices (17 g/8 oz) and ingested daily.

ADVERSE EFFECT:

When compared to sorbitol or lactulose, PEG does not produce significant cramps or flatus.

DRUG INTERACTION

This laxative may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS

Undiagnosed intestinal obstruction and paralytic ileus

3. STIMULANT LAXATIVES OR CATHARTICS

DRUG USED

• Castor Oil
• Bisacodyl 

MODE OF ACTION: It is hydrolyzed in the upper small intestine to ricinoleic acid, a local irritant that causes direct stimulation of the enteric nervous system and also increases colonic electrolyte and fluid secretion. This will increase peristalsis.

DOSE AND ROUTE OF ADMINISTRATION

USES: Cathartics may be required on a long-term basis, especially in patients who are suffering from chronic constipation due to neurologically impaired and also chronic constipation in bed-ridden patients.

Castor Oil dose:

 1 teaspoon full is usually recommended for adults once daily for 3-7 days. Nowadays castor oil bottle is provided with measuring cup and it should be taken as prescribed by treating doctor.

Bisacodyl dose:

Constipation (Adult):

1. a) 5-15 mg once daily up to 30 mg/day
2. b) 10 mg suppository rectally once daily

 Preparation of bowel for the procedure :

1. a) 10-15 mg once daily up to 30 mg/day
2. b) 10 mg suppository rectally once daily

 Onset: bowel movement within 15 to 60 min.

ADVERSE EFFECT

Long-term use of cathartics may lead to dependency and destruction of the myenteric plexus, resulting in colonic atony (loss of tone of colon smooth muscle) and dilation.

DRUG INTERACTION

This laxative may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS

Undiagnosed intestinal obstruction, paralytic ileus and atonic colon (loss of intestinal muscle tone)

4. STOOL SURFACTANT AGENTS (STOOL SOFTENERS)

DRUGS USED:

• Docusate 
• Glycerin (Suppository)
• Mineral Oil

These are also called as lubricants or emollient.

MODE OF ACTION:

• Docusate (enteral or enema) or glycerin suppository: These agents soften stool material, permitting water and lipids to penetrate.

• Mineral oil (clear and viscous oil) lubricates faecal material, retarding colonic water absorption from the stool. They make the stool slippery so that they can slide through the lumen of the intestine.

• These drugs usually act as a surfactant in the small and large intestine, enabling additional water and fats to be incorporated in the stool, making it easier to move. 

DOSE AND ROUTE OF ADMINISTRATION

Docusate : 50, 100, 250 mg capsules; 100 mg tablets; 20, 50, 60, 150 mg/15 mL syrup

Glycerin liquid Rectal liquid: 4 mL per applicator

Rectal Glycerin suppository

USES:

Docusate (Enteral route or enema) or Glycerin (suppository): In hospitalized patients, docusate is commonly prescribed to prevent constipation and minimize straining.

Mineral oil: It is used to prevent and treat faecal impaction in young children and debilitated adults.

ADVERSE EFFECT:

Aspiration can result in severe lipid pneumonitis. Long-term use can impair the absorption of fat-soluble vitamins (A, D, E, K).

DRUG INTERACTION:

Stool Softeners + administration of fat-soluble vitamin preparation containing A, D, E or  K leads to impaired absorption these vitamins.

CONTRAINDICATIONS:

Concurrent administration of fat-soluble vitamins A, D, E or K

 

5. ANTHRAQUINONE DERIVATIVES

These are Natural product from plants

DRUGS USED:

• Senna
• Cascara

MODE OF ACTION: These laxatives are poorly absorbed and after hydrolysis in the colon, induce bowel movements in 6–12 hours when given by enteral route and within 2 hours when given rectally.

DOSE AND ROUTE OF ADMINISTRATION

Senna : 8.6, 15, 17, 25 mg tablets; 8.8, 15 mg/mL liquid

Cascara sagrada : 325 mg tablets; 5 mL per dose fluid extract (approximately 18% alcohol)

USES: Chronic constipation

ADVERSE EFFECT: Chronic use leads to a characteristic brown pigmentation of the colon

known as "melanosis coli." There has been some concern that these agents may be carcinogenic

ADVERSE EFFECT

Long-term use of cathartics may lead to dependency and destruction of the myenteric plexus, resulting in colonic atony (loss of tone of colon smooth muscle) and dilation.

DRUG INTERACTION

This laxative may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS

Undiagnosed intestinal obstruction, paralytic ileus and atonic colon (loss of intestinal muscle tone)

PURGATIVES

• Purgatives tend to cleanse or purge, especially causing the evacuation of the bowels. Purgatives have a more powerful effect than laxatives.
• High doses of osmotically active agents produce prompt bowel evacuation (purgation) within 1–3 hours.
• The rapid movement of water into the distal small bowel and colon leads to a high volume of liquid stool followed by rapid relief of constipation.

DRUGS USED:

• Magnesium Citrate
• Sodium Phosphate

MODE OF ACTION:

• These drugs absorb water in the intestines. So Increased water content in the intestine stimulates the intestine and initiates peristalsis (Fig. 5.3.5)

Note: Magnesium Citrate is also considered as a saline laxative.

DOSE AND ROUTE OF ADMINISTRATION

MAGNESIUM CITRATE: (1.745g per fl oz / fluid ounce)

Adults and Children: 12 years of age and older 1/2 to 1 bottle. Drink a full 8 oz glass of liquid with each dose. The dose may be taken as a single daily dose or in divided doses.

Children 6 to under 12 years of age: 1/3 to 1/2 bottle with a full 8 oz glass of liquid.

Children under 6 years of age: As directed by the doctor

SODIUM PHOSPHATE ENEMA:

Adults & children 12 years and over: one bottle once daily

Children 2 to under 12 years: ½ bottle once daily

Children 2 years: Not recommended

USES:

Magnesium Citrate: To relieve occasional constipation (irregularity) and generally it produces bowel movement in 1/2 to 6 hours.

Sodium Phosphate: To evacuate bowel before Colonoscopy, surgery, x-rays, or other intestinal procedures.

ADVERSE EFFECT:

Magnesium Citrate:

• Dizziness, nausea, and sweating.
• In some individuals, magnesium citrate cause allergic reactions such as swelling, difficulty breathing, or Urticaria (skin rash)

DRUG INTERACTION:

Purgatives may cause decreased absorption of other medications Ex: theophylline, digoxin, phenytoin, phenobarbital

CONTRAINDICATIONS: Elderly patients, renal insufficiency, or in cardiac disease as they cause intravascular volume depletion and electrolyte fluctuations.

Procedure for administering sodium phosphate enema:

Remove green protective shield before inserting. Hold bottle upright, grasping bottle cap with fingers. Grasp protective shield with other hand and pull gently to remove.

Positioning:  

Left-side position: lie on the left side with knee bent and arms at rest. 

Knee-chest position: kneel, then lower head and chest forward until the left side of the face is resting on the surface. Position arms comfortably. 

Administering enema:

• Apply gentle and steady pressure, gently insert enema with tip pointing toward navel.
• squeeze bottle until recommended dose is expelled (it is not necessary to empty unit completely. The bottle contains more liquid than needed for effective use.
• A small amount of liquid will remain in bottle after squeezing).
• Then remove the tip from rectum
• Stop using if the tip is hard to insert. Forcing the tip into the rectum can cause injury (especially if you have haemorrhoids). If enema tip causes rectal bleeding or pain, get immediate medical care.
• maintain position until urge to evacuate is strong (usually 1 to 5 minutes)
• If you find that no urge is felt after 5 minutes of using, try to empty bowel.
• Call the doctor promptly if no liquid comes out of the rectum after 30 minutes because dehydration could occur.