PREPARED BY SALMAN HABEEB

DRUGS AFFECTING GASTROINTESTINAL

SYSTEM

COMMONLY DRUGS USED • EMETICS • ANTIEMETICS• PROKINETICS• PURGATIVES• ANTACIDS• ANTIDIARRHOEALS• ANTIULCERS• CARMINATIVES• ANORECTAL PREPARATIONS

EMETICS • EMESIS =?

DRUGS THAT PRODUCE/ INDUCE VOMITING IS CALLED EMETIS

MECHANISM OF VOMITING• WHAT IS VOMITING?•  It is the forceful expulsion of the contents

of the stomach via the mouth or sometimes through the nose.

• The vomiting reflex is stimulated by two centers in the medulla

1 . vomiting center 2 .chemoreceptor trigger zone(CTZ)

How this CTZ is stimulated• Tactile stimulation of the back of the

throat, a reflex to get rid of something that is too big or too irritating to be swallowed

• Excessive stomach distention• Increasing intracranial pressure by

direct stimulation• Stimulation of the vestibular

receptors in the inner ear

• Intense pain fiber stimulation• Direct stimulation by various chemicals,

including fumes, certain drugs, and debris from cellular death

• CTZ is stimulated by several different processes and initiates a complex series of responses that first preparet he system for vomiting and then cause a strong backward peristalsis to rid the stomach of its contents.

Classification of Emetics 1.Stimulants of CTZ a.Apomorphine b.Morphine2.Irritants of gastric mucosa a.mustard b.sodium chloride3.Both CTZ stimulant and irritant effect a.ipecacuanha b.digitalis

Apomorphine• It is obtained by treating morphine

with HCL• MECHANISM?• Produce vomiting in 5-10 minutes

after admn• Dose- 2 to 4mg• Route- subcutaneous/IM

MUSTARD• It is a household remedy to induce

vomiting• Dose- 1teaspoonful with water

Ipecacuanha• It is obtained from the dried  rhizome

and roots of carapicheae ipecacuanha from which it derives its name.

• Commonly available as syrup• Dose- 15 to 20ml• Induce vomiting witin 15 minutes

Antiemetics • Drugs that prevent vomiting

CLASSIFICATION1.Prokinetics a.metochlorpramide b.domperidone2.Antimuscarinics a.hyocine b.meclozine3.Antihistamines a.cyclizine b.promethazine(phenergan)4.Neuroleptics a.chlorpromazine b.prochlorpromazine5. 5-HT3 antagonists a.ondancetron b.granicetron

Prokinetics• These drugs which promote gastrointestinal

motility and quicken gastric emptying• Metoclorpramide(REGLAN) It has both central and peripheral effects Central- blocks the dopeminergic receptors peripheral- increased gastric emptying dose- 5- 10 mg

Metochlopramide(reglan) • Dose- 5-10 mg• Indications post-operative vomiting, vomiting during induction of anesthesia• Side effects: restlessness, drowsiness, dizziness, and or dystonic reactions.

Domeperidone • Action- Block the dopaminergic

receptors in the upper GIT• Dose- 10mg,30mg tablets 1mg/ml syrup

Side effects: Headache, dizziness, dry mouth, nervousness, flushing, or irritability

Antimuscarinics• Action- Competitively inhibits action

of acetylcholine at muscarinic receptors

• Hyoscine –very effective in controlling motion sickness

• Dose -0.4-0.6 mg po 30 min before journey

• It is a labrynthine sedative

Neuroleptics• Action- they act by suppressing the

CTZ so they antagonize vomiting produced by drugs which stiimulate CTZ

Eg; chlorpromazine • dose; PO: 10-25 mg q4-6hr IV/IM: 25-50 mg q4-6hr

5-HT3 Antagonists•  (5-HT3) receptor antagonists block

the vomiting reflex by inhibiting 5-HT3 receptors in the vomiting center , the chemoreceptor trigger zone and in the small intestine

Ondansetron(Emeset)• Blocks 5HT3 receptors in git and CTZ • Specially used In chemotherapy,post

op vomiting other drug induced vomiting

• Dose- 4mg in each ampule • 4,8 mg tab

• Side effects: Headache, constipation, and dizziness are the most commonly reported side effects associated with its use

Granisetron• It is 10 to 15 times more potent than

ondansetron• More effective in chemotherapy • Dose – IV 1mg

Antihistamines• They act by sedating the vomiting

centre• They are safer for long term use• Effective in motion sickness and

vomiting due to labrynthine disoders eg. Cyclizine meclozine dose- 50mg/ml inj 50mg tab

Nursing Considerations for Patients Receiving

an Antiemetic Agent• Assess for possible contraindications

or cautions history of allergy to antiemetic to avoid potential hypersensitivity reactions; impaired renal or hepatic function

• ■ Assess the patient’s neurological status, including level of orientation, affect, and reflexes,

• ■ Examine the abdomen, including the liver, and auscultate bowel sounds

• ■ Assess complaints of nausea and evaluate emesis; note color, amount, and frequency of vomiting episodes

• Instruct the client to avoid over-the-counter preparations.

• Instruct the client not to consume alcohol while taking antiemetics.

• Advise pregnant women to avoid antiemetics during the first trimester.