Gastrointestinal Drugs, Bowel

1. VN 225 - Nursing Applications of Pharmacology

Gastrointestinal Drugs, Bowel

2. Drugs affecting the large bowel

Laxative & cathartics

Laxative = milder action, solid or soft feces

Cathartic = stronger action, liquid feces

Bowel cleansing = entire bowel free of feces, clear liquid bowel movement. Prior to bowel procedures

3. A & P Bowel

4. Drugs affecting large bowel

Bulk forming laxatives: Psyllium (Metamucil), methylcellulose (Citrucel)


Add bulk by absorbing water to make mushy feces

Not digested, most physiologic, similar to high fiber diet

Time to bowel movement

One to three days


Dry powder, mix just before giving, forms a gel. Give plenty of fluids

For tube feedings, mix with lots of water and force through tube quickly

5. Drugs affecting large bowel

Surfactant laxative: docusate (Colace, Surfak)


Acts like detergent to soften fecal mass

Used to prevent hard feces; can be used with bulk laxatives

Time to bowel movement

One to three days


Give regularly. Don't open capsule, tastes awful

Available in liquid for feeding tubes

6. Drugs affecting large bowel

Saline Laxatives (magnesium citrate; magnesium hydroxide; phosphosoda (Fleets) oral preparations

Action: for occasional use only

Draw fluid into bowel lumen, forming liquid, fast transit feces

Time to bowel movement

One to 6 hours


When prevention has been ignored and patient is constipated

When rapid action is needed

Occasionally, oral Fleets used for bowel cleansing

7. Drugs affecting large bowel

Saline oral laxatives


Tastes awful. Serve chilled, with a straw, and a chaser. More water to prevent vascular dehydration

Saline enemas (Fleets phosphosoda)

Action: Draws water into the rectum to promote bowel movement. Not effective for impactions


Follow instructions on package

Have patient hold the fluid as long as possible

8. Drugs affecting bowel

Stimulant cathartics: bisocadyl; (Docusate); Cascara, senna (Senakot), and castor oil


Irritates the GI mucosa, pulls water into bowel lumen causing rapid transit of liquid stool

Should probably not be used

Advantage: available in tablet form (except castor oil)

Time to bowel movement

Six to twelve hours

9. Drugs affecting bowel

Rectal suppositories: glycerin, bicosadyl (Ducolax)


Irritates mucosa of anal & rectal mucosa

Draws water into bowel lumen & promotes bowel movement


Unconscious or vegetative state patients to promote bowel movement, often used daily

Occasional use to promote immediate bowel movement

Nursing - same as for Fleets enema

10. Drugs affecting bowel

Polyethylene glycol with electrolytes


Large molecule (PEG), not absorbed

Electrolytes to prevent movement of water from the bowel or into the bowel

4 L, 1 gallon, given orally or by nasogastric tube

Uses: bowel cleansing


Serve cold, with straw, and encouragement

Continue with 8 ounces every 10 minutes until effluent is clear

11. Drugs affecting bowel

Polyethylene glycol without electrolytes (MiraLax)


Large molecule (PEG) holds water in the lumen

Not absorbed, much smaller dose than for bowel cleansing

Time to bowel movement

One to two days


Stir into water or juice and allow time to dissolve before giving

12. Drugs affecting bowel


A non-digested sugar, tastes sweet, draws water into bowel lumen


For chronic constipation, can be used for children

For treatment of high ammonia levels in liver failure

Diarrhea eliminates some of the fecal bacteria that produce ammonia

Diarrhea necessary for therapeutic action

13. Drugs affecting bowel

Mineral oil

Not to be given orally - risk for aspiration of oil

Used as enema for impactions - to ease removal of feces

14. A & P Diarrhea

Definition: frequent, liquid stools (bowel movements)


Infections with bacteria, virus, or protozoa, usually from contaminate food or fecal-oral transmission

Short gut secondary to surgery

Lack of digestive enzymes

Inflammatory bowel disease

15. A & P Diarrhea

Effects of severe diarrhea

Fluid volume loss

Electrolyte imbalances (loss of potassium, sodium)

Death in infants, young children, and elderly


Replacement of fluid & electrolytes

Oral : WHO recipe or Pedialyte

Intravenous not required, but used in emergency dept.

16. Drugs affecting bowel

Antidiarrheal medications: diphenoxylate with atropine (Lomitil); loperimide (Imodium)

Derivatives of meperidine (Demerol), acts like an opiate. Atropine is to prevent street use.


Control diarrhea when necessary.

Does not treat cause

17. Drugs affecting bowel

Antidiarrheal drugs


Give as ordered when necessary

May be used to prevent breakdown of perianal skin

Protect skin with heavy ointments and frequent cleaning