Drugs used in irritable bowel syndrome (IBS) Emetics and Anti-emetics

Question 1

What are spasms?

Answer 1

Spasms are sudden and involuntary muscular contractions, most often accompanied by pain.

Spasms can occur in both smooth and skeletal muscles.

Pain or discomfort of the gastrointestinal tract may be associated with spasm of the smooth muscle of the bowel.

Intestinal spasm is the uncontrolled muscle contraction of the large and small intestines.

It may also be accompanied by bloating, abdominal distention, diarrhoea and constipation.

Such pain and spasm may be associated with the irritable bowel syndrome (IBS)

Question 2

What is irritable bowel syndrome?

Answer 2

Irritable bowel syndrome (IBS) is believed to be a disorder of GI motility, particularly in the colon.

GI disorder characterized by crampy abdominal pain—sometimes severe—occurring in association with diarrhea, constipation, or both.

Patients experience diarrhea, constipation, or both episodes with significant GI cramping.

Question 3

Common symptoms of IBS

Question 4

What are types of Antispasmodic agents?

Answer 4

Anti-muscarinics drugs
Direct smooth-muscle relaxants
Calcium channel blockers

Question 5

What are Anti-muscarinics drugs and examples?

Answer 5

The actions of muscarinic receptor antagonists on the abdominal smooth muscle led to the use of muscarinic receptor antagonists as antispasmodic agents for GI disorders.

• Butylscopolamine (hyoscine)
• Di-cyclo-verine hydrochloride (Dicyclomine)
• Cimetropium bromide.
• Glycopyrrolate

Question 6

Direct smooth-muscle relaxants

Answer 6

• Mebe-verine
• Papa-verine
• Peppermint oil

Question 7

Calcium channel blockers

Answer 7

• Otilo-nium bromide
• Alverine citrate
• Pina-verium bromide

Question 8

Which Antimuscarinic is well-absorbed when applied to skin?

Answer 8

hyoscine

Question 9

What are emetics and what is vomiting?

Answer 9

•Emetics are drugs that causes vomiting.

•Vomiting is the involuntary forceful expulsion of stomach contents through the mouth.

Question 10

What are the Phases of vomiting?

Answer 10

•1. Nausea:- this the sensation or urge to vomit, which may be accompanied by increased salivation, pupillary dilation, sweating, and pallor.

•2. Retching:- a violent spasmodic movement against a closed glottis without expulsion of gastric contents.

•3. Vomiting:- a this stage there’s a sustained contraction of the diaphragm and stomach muscles resulting in involuntary forceful evacuation of the stomach contents through the mouth.

Question 11

Discuss emetic stimuli

Answer 11

Emetic stimuli
•The vomiting centre is located at the fourth ventricle of the brain.

• The floor of the fourth ventricle contains an area called the chemoreceptor trigger zone (CTZ) also called the area postrema. When the CTZ is stimulated, vomiting may occur.

•The vestibular system of the inner ear involved in motion system has abundant H1 receptors. Inputs from the vestibulocochlear nerve sends signals to the CTZ.

•Vagus nerve sends inputs to the CTZ when the throat is irritated (gag reflex)

Question 12

What are the most commonly used emetics?

Answer 12

1. Apo-morphine (acts directly on the CTZ)
2. Ipeca-cuan-ha (acts reflexly and directly on the CTZ)

Question 13

What is a reason to give a patient emetics?

Answer 13

Induced emesis is the preferred means of emptying the stomach in awake patients who have ingested toxic substance or have recently taken a drug overdose.

Question 14

APOMORPHINE and adverse effects

Answer 14

is a semi synthetic derivative of morphine; acts directly on the CTZ as a dopaminergic agonist.

Oral use of apomorphine is not recommended because a high dose is required with slow and inconsistent action.

•Although it may be more effective if water is first administered before oral or subcutaneous dosing.

•Excessive dosage may cause respiratory depression and circulatory collapse.

Question 15

What are Contraindications of Emetics?

Answer 15

•Emesis SHOULD NOT be induced if;

1.The patient is unconscious. The patient is likely to aspirate the vomitus because laryngeal reflex is likely to be impaired.

1.The patient has central nervous system depression .

2.Corrosive acid or alkali is ingested.

3.Certain volatile hydrocarbons (Kerosine, petroleum products) are ingested. This can cause more injury to the oesophageal mucosa.

4.CNS stimulant drug poisoning: it may precipitate convulsion.

6. It is morphine or phenothiazine poisoning: Emetics are ineffective

Question 16

What are Anti-emetics?

Answer 16

•Antiemetics may prevent emesis either by blocking the CTZ or by preventing peripheral or cortical stimulation of the vomiting center.

•They are classified based on the receptors on which they act.

•The antiemetics used in the treatment and prevention of nausea and vomiting associated with cancer chemotherapy are often a combination of agents in different pharmacological class.

Question 17

What is the Classification and examples of antiemetics?

Answer 17

1.Antimuscarinic. (Hyoscine, Dicycloverine)

2.Antihistamines. (Promethazine, Diphenhydramine, Dimenhydrinate, Doxylamine, Cyclizine, Meclozine, Cinnarizine.)

3.5-HT3 receptor antagonists. (Ondansetron, Granisetron, Dolasetron, Palonosetron)
4.Dopamine receptor antagonists. (Metoclopramide, Lorazepam, Haloperidol)

5.Neurokinin receptor antagonists. (Aprepitant, Fos-aprepitant)

6.Cannabinoid receptor agonists. (Dronabinol, nabilone)

Question 18

What is the most commonly used and effective antimuscarinic for motion sickness?

Answer 18

Hyoscine (scopolamine)

Question 19

Which anti-histamine is useful in treating the nausea and vomiting subsequent cancer chemotherapy?

Answer 19

promethazine

Question 20

What is the main function of anti-histamines?

Answer 20

Their combination is used in chemotherapy induced vomiting.

Whenever possible, the various drugs should be administered approx. 1 hour before the anticipated motion. Treatment after the onset of nausea and vomiting rarely is beneficial.

Only promethazine is useful in treating the nausea and vomiting subsequent cancer chemotherapy. However, other more effective anti-emetic drugs (e.g., 5-HT3 antagonists) are available.

Cyclizine has additional anticholinergic effects that may be useful for patients with abdominal cancer.

Question 21

Main function of 5-HT3 receptor antagonists?

Answer 21

The 5-HT3 receptor antagonists are the most widely used drugs for chemotherapy-induced emesis and post operative nausea & vomiting.

•They also are effective against hyperemesis of pregnancy, but not against motion sickness.

Question 22

Adverse effects of 5HT3 antagonists

Answer 22

•These drugs are generally well tolerated.

•The most common side effects are headache, lightheadedness, mild constipation or diarrhoea and abdominal discomfort occur in few patients.

•Rashes and allergic reactions has been, especially after i.v injection.

Question 23

Adverse effects of Dronabinol

Answer 23

•Dronabinol has complex effects on the CNS, including a prominent central sympathomimetic activity. This can lead to palpitations, tachycardia, vasodilation, hypotension, increase in appetite and conjunctival injection (bloodshot eyes).

Question 24

Ipecacuanha and adverse effects

Answer 24

Ipecacuanha is obtained from the dried rhizome and roots of Cephaelis ipecacuanha or Cephaelis acuminata, plants in Brazil and Central America that have the alkaloid emetine as their active principal ingredient.

It is administered as ipecac syrup (15-30ml in adults, 10-15 ml in children, 5 ml in infants) for inducing vomit.

It acts directly on the CTZ and also indirectly by irritating the gastric mucosa.

It should be available in every household for emergency.

It is less dependable than parenteral apomorphine and takes 15 minutes or more to produce the effect but is safer.

Ipecac is cardiotoxic if absorbed and can cause cardiac conduction disturbances, atrial fibrillation, or fatal myocarditis.

If emesis does not occur, gastric lavage using a nasogastric tube must be performed.