NurseReview.Org - Pharmacology Git Drugs

Pharmacology of the GIT system

LECTURE Outline
REVIEW the Anatomy of the GIT
REVIEW the Physiology of the GIT
Review common GI drugs in the following categories:
1. Drugs affecting GI secretions
2. Laxatives
3. Anti-diarrheals
4. Emetics and anti-emetics

Fig. 16.1

Fig. 16.10a

Fig. 16.10b

Fig. 16.11a

Fig. 16.11b

Fig. 16.12

Drugs affecting GI secretions
There are five types of drugs that affect gastric acid secretions and are useful for the treatment of peptic ulcer.
Histamine (H2) receptor antagonist/blockers
Antacids
Proton pump inhibitors
Mucosal protectants
Prostaglandin analogs

Drugs affecting secretions: anti ulcer Misoprostol Prostaglandin analog Sucralfate Mucosal protectants Omeprazole Proton pump inhibitors AlOH and MgOH Antacids Cimetidine Histamine (H2) receptor antagonist/blockers Prototype Anti-ulcer drugs

General indication of the drugs affecting gastric acid secretion
Peptic ulcer
Gastritis
Patient on NPO to prevent stress ulcer

General time of administration of the drugs affecting gastric acid secretion Misoprostol WITH MEALS Prostaglandin analog Sucralfate BEFORE MEALS Mucosal protectants Omeprazole BEFORE MEALS Proton pump inhibitors AlOH and MgOH Usually after meals Antacids Cimetidine With FOOD or ONE hour after ANTACID Histamine (H2) receptor antagonist/blockers Prototype Best time to give Anti-ulcer drugs

Pharmacodynamics
Histamine (H2) receptor blockers
These drugs BLOCK the release of hydrochloric acid in the stomach in response to gastrin

Antacids
These drugs interact with the gastric acids at the chemical level to neutralize them

Proton pump inhibitors
These drugs suppress the secretion of hydrochloric acid into the lumen of the stomach

Mucosal protectants
These are agents that coat any injured area in the stomach to prevent further injury from acid

Prostaglandin analogs
These are agents that inhibit the secretion of gastrin and
increase the secretion of mucus lining of the stomach, providing a buffer.

Histamine 2 receptor blockers

The H2 Blockers- “tidines”
Prototype: Cimetidine
1. Ranitidine
2. Famotidine
3. Nizatidine

Pharmacodynamics: Drug Action
The H2 blockers are antagonists at the receptors in the parietal cells of the stomach.
The blockage results to inhibition of the hormone gastrin.
There will be decreased production of gastric acid from the parietal cells.
Also, the chief cells will secrete less pepsinogen.

Therapeutic use of the H2 blockers
Short-term treatment of active duodenal ulcer or benign gastric ulcer
Treatment of hypersecretory conditions like the Zollinger-Ellison syndrome
Prevention of stress-induced ulcers and acute GI bleeding
Treatment of erosive GERD (reflux disease)
Relief of Symptoms of heart burn and acid indigestion

Precautions and Contraindications
Any known allergy is a clear contraindication to the use of the agents.
Conditions such as pregnancy, lactation, renal dysfunction and hepatic dysfunction should warrant cautious use.
Nizatidine can be used in hepatic dysfunction.

Dynamics- Side effects/adverse effects
GIT= diarrhea or constipation
CNS= Dizziness, headache, drowsiness, confusion and hallucinations
Cardio= arrhythmias, HYPOTENSION (related to H2 receptor blockage in the heart)
Cimetidine= Gynecomastia and impotence in males

Drug-drug Interactions
Cimetidine, Famotidine, Ranitidine are metabolized in the liver- they can cause slowing of excretion of other drugs leading to their increased concentration .

Drug-drug Interactions
These drugs can interact with CIMETIDINE
Anticoagulants
Phenytoin,
Alcohol
Antidepressants.

Nursing considerations:
Administer the drug WITH meals at BEDTIME to ensure therapeutic level
One hour after Antacids
Stress the importance of the continued use for the length of time prescribed

Nursing considerations
Monitor the cardiovascular status especially if the drugs are given IV
Warn patient of the potential problems of increased drug concentration if the H2 blockers are used with other drugs or OTC drugs. Advise consultation first!

Provide comfort measures like analgesics for headache, assistance with ambulation and safety measures because of confusion
Warn the patients taking cimetidine that drowsiness may pose a hazard if driving or operating delicate machines.

Provide health teaching as to the dose, frequency, comfort measures to initiate when side-effects are intolerable
Evaluate the effectiveness
Relief of symptoms of ulcer, heart burn and GERD

Antacids

The Antacids
These are drugs or inorganic chemicals that have been used for years to neutralize acid in the stomach

The Antacids
The following are the common antacids that can be bought OTC:
Aluminum salts (hydroxide)
Calcium salts (carbonate)
Magnesium salts (milk of magnesia)
Sodium bicarbonate
Magaldrate (aluminum and magnesium combination)

The Antacids
Pharmacodynamics: drug action
These agents act to neutralize the acidic pH in the stomach.
They do not affect the rate of gastric acid secretion.

The Antacids
The administration of antacid may cause an acid rebound.
Neutralizing the stomach content to an alkaline level stimulates gastrin production to cause an increase in acid production and return the stomach to its normal acidic state.

The Antacids
Therapeutic Indications
Symptomatic relief of upset stomach associated with hyperacidity
Hyperacidic conditions like peptic ulcer, gastritis, esophagitis and hiatal hernia
Special use of AMPHOGEL (aluminum hydroxide): to BIND phosphate

The Antacids
Precautions of Antacid Use
Known allergy is a clear contraindication
Caution should be instituted if used in electrolyte imbalances, GI obstruction and renal dysfunction.
Sodium bicarbonate is rarely used because of potential systemic absorption  metabolic alkalosis!!!

The Antacids
Pharmacokinetics
These agents are taken orally and act locally in the stomach

The Antacids
Pharmacodynamics: Effects of drugs
GIT= rebound acidity; alkalosis may occur.
Calcium salts may lead to hypercalcemia
Magnesium salts can cause DIARRHEA
Aluminum salts may cause CONSTIPATION and Hypophosphatemia by binding with phosphates in the GIT.
2. Fluid retention due to the high sodium content of the antacids.

The Antacids
Nursing Considerations:
Administer the antacids apart from any other medications by ONE hour before or TWO hours after- to ensure adequate absorption of the other medications
Tell the patient to CHEW the tablet thoroughly before swallowing. Follow it with one glass of water
Regularly monitor for manifestations of acid-base imbalances as well as electrolyte imbalances

The Antacids
Nursing Considerations:
Provide comfort measures to alleviate constipation associated with aluminum and diarrhea associated with magnesium salts.
Monitor for the side-effects, effectiveness of the comfort measures, patient’s response to the medication and the effectiveness of the health teachings

The Antacids
Nursing Considerations
Evaluate for effectiveness:
Decreased symptoms of ulcer and pyrosis
Decreased Phosphate level (Amphogel) in patients with chronic renal failure

proton-pump inhibitors

The PPI
These are the newer agents for ulcer treatment
The “prazoles”
Prototype: Ome prazole
Laniso prazole
Esome prazole
Panto prazole

The PPI
They act at specific secretory surface receptors to prevent the final step of acid production and thus decrease the level of acid in the stomach.
The “pump” in the parietal cell is the H-K ATPase enzyme system on the secretory surface of the gastric parietal cells

The PPI
Clinical use of the PPIs
Short-term treatment of active duodenal ulcers, GERD, erosive esophagitis and benign gastric ulcer
Long-term- maintenance therapy for healing of erosive disorders.

The PPI
Precautions with the use of the PPIs
Known allergy is a clear contraindication
Caution if patient is pregnant

The PPI
Pharmacodynamics: Adverse effects
CNS- dizziness , headache, asthenia (loss of strength), vertigo , insomnia, apathy
GIT- diarrhea, abdominal pain, nausea, vomiting, dry mouth and tongue atrophy
Respi- cough, stuffy nose, hoarseness and epistaxis.

The PPI
Administer the drug BEFORE meals. Ensure that patient does not open, chew or crush the drug.
Provide safety measures if CNS dysfunction happens.
Arrange for a medical follow-up if symptoms are NOT resolved after 4-8 weeks of therapy.

The PPI
Provide health teaching as to drug name, dosages and frequency, safety measures to handle common problems.
Monitor patient response to the drug, the effectiveness of the teaching plan and the measures to employ

The PPI
Evaluate for effectiveness of the drug
Healing of peptic ulcer
Decreased symptoms of ulcer

Mucosal protectants

The Mucosal Protectant
Sucralfate (Caralfate/ Iselpin)
This is given to protect the eroded ulcer sites in the GIT from further damage by acid and digestive enzymes

Sucralfate
Pharmacodynamics: Action of drug
It forms an ulcer-adherent complex at duodenal ulcer sites, protecting the sites against acid, pepsin and bile.
This action prevents further breakdown of proteins in the area and promotes healing.

Sucralfate
Clinical use of sucralfate
Short and long term management of duodenal ulcer.
NSAIDs induced gastritis
Prevention of stress ulcer
Treatment of oral and esophageal ulcers due to radiation, chemotherapy or sclerotherapy.

Sucralfate
Precautions on the use of Sucralfate
This agent should NOT be given to any person with known allergy to the drug, and to those patients with renal failure/dialysis because of build-up of aluminum may occur if used with aluminum containing products.

Pharmacodynamics: Side-effects & adverse reactions
Primarily GIT= CONSTIPATION, occasionally diarrhea, nausea, indigestion, gastric discomfort, and dry mouth may also occur
CNS= dizziness, drowsiness, vertigo
Others= rash and back pain

Drug-drug interactions
If used with aluminum salts= high risk of accumulation of aluminum and toxicity .
If used with phenytoin, fluoroquinolones and penicillamines- decreased levels of these drugs when taken with sucralfate

Administer drug ON AN EMPTY stomach , 1 hour before meals , or 2 hour after meals and at BEDTIME
Monitor for side-effects like constipation and GI upset
Encourage intake of high-fiber foods and increased fluid intake
Administer antacids BETWEEN doses of sucralfate, NOT WITHIN 30 minutes of sucralfate dose

Provide comfort measures if CNS effects occur
Monitor patient response to the drug, the effectiveness of the teaching plan and the measures employed

Evaluate effectiveness of therapy
Healing of ulcer
No formation of ulcer

Prostaglandin analogue

Misoprostol
This agent is a synthetic prostaglandin E1 analog that is employed to protect the lining of the mucosa of the stomach

Misoprostol: Pharmacodynamics
Being a prostaglandin analog, it inhibits gastric acid secretion to some degree
It INCREASES mucus production in the stomach lining.

Misoprostol: Clinical use
NSAIDs-induced gastric ulcers
Duodenal ulcers unresponsive to H2 antagonists

Precautions of Misoprostol Use
This drug is CONTRAINDICATED during pregnancy because it is an abortifacient.
Women should be advised to have a negative pregnancy test within 2 weeks of beginning therapy and should begin the drug on the second or third day of the next menstrual cycle.
They should be instructed in the use of contraceptives during therapy.

Pharmacodynamic effects: drug reactions
GIT= Nausea, diarrhea, abdominal pain, flatulence, vomiting, dyspepsia
GU effects= miscarriages, excessive uterine CRAMPING and bleeding , spotting, hyper-menorrhea and menstrual disorders.

Administer to patients at risk for NSAIDs-induced ulcers during the full course of NSAIDs therapy
Administer four times daily with meals and at bedtime
Obtain pregnancy test within 2 weeks of beginning therapy.
Begin the therapy on second or third day of menstrual period to ensure that the woman is not pregnant

Provide patient with both written and oral information regarding the associated risks of pregnancy
Monitor patient response to the drug, the effectiveness of the teaching plan and the measures to employ

laxatives

Laxatives
Generally used to INCREASE the passage of the colonic contents
The general classifications is as follows:
1. Chemical stimulants- irritants
2. Mechanical stimulants- hyperosmotic agents and saline cathartics
3. Lubricants and stool softeners

Laxatives
They promote bowel evacuation for various purposes
They are classified into their mode of action

Laxatives Lubricating the intestinal material to promote passage through the GIT Docusate Mineral oil Lubricants Increased fluid content of the fecal material causing stimulation of the local reflex Lactulose Mechanical (bulk) stimulants Direct stimulation of the GIT nerves Irritant laxatives Bisacodyl (Dulcolax) Chemical stimulants Action Prototype Type

Therapeutic Indications of the Laxatives
SHORT term relief of Constipation
Prevention of straining in conditions like CHF, post-MI, post partum, post-op
Preparation for diagnostic examination
Removal of poison or toxins
Adjunct in anti-helminthic therapy
To remove AMMONIA by use of lactulose

Contraindications in Laxative use
ACUTE abdominal disorders
Appendicitis
Diverticulitis
Ulcerative colitis

Chemical Stimulant Cathartics
Prototype: Bisacodyl
Irritant laxatives:
1. Castor oil
2. Senna
3. Cascara
4. Phenolphthalein

Chemical Stimulant Cathartics
Pharmacodynamics
These agents DIRECTLY stimulate the nerve plexus in the intestinal wall
The result is INCREASED movement or motility of the colon

Mechanical Stimulant Cathartics
Prototype: LACTULOSE (Cephulac)
Bulk-forming laxatives
1. Magnesium ( citrate , hydroxide, sulfate)- saline cathatic
2. Psyllium
3. Polycarbophil

Mechanical Stimulant Cathartics
Pharmacodynamics
These agents are rapid-acting laxatives that INCREASE the GI motility by
Increasing the fluids in the colonic material
Stimulating the local stretch receptors
Activating local defection reflex

Lubricants-Stool softener
Prototype: Docusate
1. Glycerin
2. Mineral oil

Lubricants-stool softeners
Pharmacodynamics
Docusate increases the admixture of fat and water producing a softer stool
Glycerin and Mineral oil form a slippery coat on the colonic contents

Pharmacokinetics: Common Side-effects of the Laxatives
Diarrhea
Abdominal cramping
Nausea
Fluid and electrolyte imbalance
Sympathetic reactions- sweating, palpitations, flushing and fainting
CATHARTIC dependence

The Nursing Process and Laxative
ASSESSMENT
Nursing History- elicit allergy to any laxatives, elicit history of conditions like diverticulitis and ulcerative colitis
Physical Examination- abdominal assessment
Laboratory Test: fecalysis, electrolyte levels

NURSING DIAGNOSIS
Alteration in bowel pattern
Alteration in comfort: pain
Knowledge deficit

IMPLEMENTATION
Emphasize that it is use on a SHORT term basis
Provide comfort and safety measures like ready access to the bathroom, side-rails
Administer with a full glass of water

IMPLEMENTATION
4. Encourage fluid intake, high fiber diet and daily exercise
5. DO NOT administer if acute abdominal condition like appendicitis is present
6. Advise to change position slowly and avoid hazardous activities because of potential dizziness

IMPLEMENTATION
7. Record intake and output to assess fluid alteration
8. If possible, observe the character of stools
9. Caution the patient that chronic use may promote dependence and use during pregnancy may cause uterine cramping and Vitamin deficiency

EVALUATION of drug effectiveness
Evaluate relief of GI symptoms, absence of staining and increased evacuation of GI tract
For Lactulose: decreased ammonia
Nomal bowel fucntion is restored

The Anti-diarrheals
These are agents used to calm the irritation of the GIT for the symptomatic relief of diarrhea
General Classifications
1. Local anti-motility
2. Local reflex inhibition
3. Central action on the CNS

The Anti-diarrheals Stops GIT spasm by CNS action Opium derivatives (paregoric) Central acting agent Directly inhibits the intestinal muscle activity to SLOW peristalsis Loperamide Local anti-motility Locally coats the lining of the GIT to soothe irritation Bismuth subsalicylate Local reflex inhibitor Action Prototype Type

Clinical Indications of drug use
Relief of symptoms of acute and chronic diarrhea
Reduction of fecal volume discharges from ileostomies
Prevention and treatment of traveler's diarrhea

Contraindications of anti-diarrheal Use
Poisoning
Drug allergy
GI obstruction
Acute abdominal conditions

Pharmacokinetics: Side effects
Constipation
Nausea, vomiting
Abdominal distention and discomfort
TOXIC MEGACOLON

Nursing process and anti-diarrheals
ASSESSMENT
Nursing History – Elicit history of drug allergy, conditions like poisoning, GI obstruction and acute abdominal conditions
Physical Examination- Abdominal examination
Laboratory test- electrolyte levels

NURSING DIAGNOSIS
Alteration in bowel pattern

IMPLEMENTATION
Monitor patient response within 48 hours. Discontinue drug use if no effect
Provide comfort measures for pain
Provide teaching regarding its short term use only

EVALUATION
Monitor effectiveness of drug- RELIEF of diarrhea
Monitor adverse effects, effectiveness of pain measures and effectiveness of teaching plan

Emetic and anti-emetics

Emetics and Anti-emetics
Emetic Agent
Syrup of Ipecac
Anti-emetics
1. Phenothiazines
2. Non-phenothiazines
3. Anticholinergics/Antihistamines
4. Serotonin receptor Blockers
5. Miscellaneous

EMETIC
Prototype: Ipecac Syrup

EMETIC
Pharmacodynamics
Ipecac syrup irritates the GI mucosa locally, resulting to stimulation of the vomiting center
It acts within 20 minutes

EMETIC
Clinical Use of ipecac
To induce vomiting as a treatment for drug overdose and certain poisonings

EMETIC
Contraindications of Ipecac use
Ingestion of CORROSIVE chemicals
Ingestion of petroleum products
Unconscious and convulsing patient

EMETIC
Pharmacokinetics: side effects of Ipecac
Nausea
Diarrhea
GI upset
Mild CNS depression
CARDIOTOXICITY if large amounts are absorbed in the body

Nursing process and the EMETIC
ASSESSMENT
Nursing History- elicit the exact nature of poisoning
Physical Examination- CNS status and abdominal exam

IMPLEMENTATION
Administer to conscious patient only
Administer ipecac as soon as possible
Administer with a large amount of water
Vomiting should occur within 20 minutes of the first dose . Repeat the dose and expect vomiting to occur with 20 minutes

IMPLEMENTATION
5. Provide comfort measures like ready access to bathroom, assistance with ambulation
6. Offer support

EVALUATION
Evaluate patient response within 20 minutes of drug ingestion
Monitor for adverse effects
Evaluate effectiveness of comfort measures and teaching plan

Anti-Emetics

ANTI-EMETICS
These are agents used to manage nausea and vomiting
They act either locally or centrally
In general, they may inhibit the chemoreceptor trigger zone in the medulla by blocking DOPAMINE receptor
Others act by decreasing the sensitivity of the vestibular apparatus

ANTIEMETICS Dronabinol, hydroxyzine Miscellaneous “ setron”- dolasetron Serotonin Receptor blockers Meclizine, buclizine Anticholinergics and Antihistaminics Metoclopramide Non-phenothiazines Prochlorperazine, Promethazine Phenothiazines Common examples Anti-emetic types

ANTIEMETICS Act in the CNS , either in the medulla or in the cortex Miscellaneous Centrally and locally inhibits the serotonin receptors Serotonin receptor blockers Block the transmission of the impulses to the medulla Anticholinergics Reduces the responsiveness of the nerve cell in the medulla; also blocks the dopamine receptors Non-phenothiazine Centrally block the vomiting center in the medulla Phenothiazines Pharmacodynamics Types

ANTIEMETICS N/V associated with chemotherapy Miscellaneous N/V associated with chemotherapy Serotonin-receptor Blockers N/V associated with motion sickness Anticholinergics N/V associated with chemical stimulation Non-phenothiazine N/V associated with anesthesia, intractable hiccups Phenothiazines Clinical Use Types

ANTIEMETICS
Indications
1. Prevention and treatment of vomiting
2. Motion sickness

ANTIEMETICS
Contraindications
1. Severe CNS depression
2. Severe liver dysfunction

ANTIEMETICS
Pharmacokinetics:
Oral absorption is good if vomiting is not present
IV drugs can be given if vomiting is active
Most drugs are metabolized in the liver excreted in the kidneys

ANTIEMETICS
Pharmacokinetics: Side-effects
1. PHOTHOSENSITIVITY
2. Drowsiness, dizziness, weakness and tremors and DEHYDRATON
3. Phenothiazines = autonomic anti-cholinergic effects like dry mouth, nasal congestion and urinary retention
Metoclopramide= EPS due to dopamine receptor blockage

Nursing Process and the ANTIEMETICS
ASSESSMENT
Nursing History- elicit allergy, impaired hepatic function and CNS depression
Physical Examination- CNS status and abdominal examination
Laboratory test- Liver function studies

NURSING DIAGNOSIS
High risk for injury
Knowledge deficit

IMPLEMENTATION
Assess patient’s intake of other drugs that may cause dangerous drug interaction
Emphasize that this is given on a short term basis

IMPLEMENTATION
3. Provide comfort and safety measures
Advise to change position slowly
Avoid hazardous activities
Provide mouth care and ice chips
Monitor for dehydration and offer fluids if it occurs

IMPLEMENTATION
4. Protect from sun exposure
Sunscreens
Protective covering
5. Provide health teaching

EVALUATION
1. Monitor for the drug effectiveness
Relief of nausea and vomiting
2. Monitor for adverse effects
3. Evaluate effectiveness of comfort measures and teaching plan

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NurseReview.Org - Pharmacology Git Drugs

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NurseReview.Org - Pharmacology Git Drugs — Presentation Transcript