Comprehensive Guide to Gastrointestinal OTC Medications: Prebiotics, Probiotics, Constipation, Diarrhea, Hemorrhoids, Gas, Nausea, Heartburn

Prebiotics

Substances that support the bacteria in the GI system (e.g., fibers like inulin from asparagus, bananas, onion, soy, wheat).

Probiotics

Live microorganisms ("friendly germs") that, in adequate amounts, confer a health benefit by crowding out harmful bacteria and improving mucosal defense.

How do prebiotics work?

Prebiotics increase growth/activity of health-promoting bacteria.

How do probiotics work?

Probiotics grow in the intestine, compete against harmful bacteria, and strengthen mucosal defenses.

Common gastrointestinal uses of prebiotics

Increase stool bulk, relieve constipation, increase calcium/magnesium absorption, lower triglycerides, increase bifidobacterium.

Common gastrointestinal uses of probiotics

Ulcerative colitis, IBS, antibiotic-associated diarrhea, necrotizing enterocolitis, prevention of C. difficile, treatment of H. pylori.

Key counseling points about probiotics and prebiotics

May cause excessive gas (decreases over time), safe in children, dairy products likely safe in pregnancy, separate probiotics and antibiotics by several hours, avoid in immunocompromised patients, discontinue if no benefit after 14 days, product variability exists.

Medications that can worsen constipation

Anticholinergics, antidepressants, verapamil, opiates, iron, calcium supplements, diuretics.

Bulk-forming laxatives

Psyllium, methylcellulose, calcium polycarbophil, inulin fiber, wheat dextrin, partially hydrolyzed guar gum, powdered cellulose.

Emollient laxatives

Docusate sodium, docusate calcium.

Lubricant laxatives

Mineral oil.

Saline laxatives

Magnesium citrate, magnesium hydroxide, magnesium sulfate, sodium phosphate.

Hyperosmotic laxatives

Glycerin, PEG 3350.

Stimulant laxatives

Senna, bisacodyl, castor oil.

Combination laxatives

Senna + docusate, senna + psyllium.

Key counseling points about OTC constipation medications

Bulk-forming: must take with plenty of water, separate from other meds by 2h. Emollient: take with water, avoid in children <6, side effects include diarrhea/cramping. Lubricant: discourage use, avoid in pregnancy/children/bedridden/dysphagia, decreases vitamin absorption. Saline: avoid in children <2 (rectal) or <5 (oral), contraindicated in ileostomy, dehydration, renal impairment, CHF. Hyperosmotic: avoid in kidney disease, side effects include bloating and diarrhea. Stimulant: may cause cramping/diarrhea, senna may discolor urine, avoid castor oil in pregnancy.

Self-care for constipation

Mild constipation without exclusions.

Referral for constipation

Severe abdominal pain, distention, cramping, blood/tarry stool, fever, persistent symptoms >2 weeks or recurring >3 months, symptoms after lifestyle changes, chronic laxative use, children <2 years, IBD, colostomy, anorexia.

Mechanism of action of laxatives

Explain the mechanism and onset of action of each class of laxatives.

Bulk-forming

Dissolve/swell to form gel, stimulate peristalsis; onset 12-72h.

Emollient

Increase stool wetting; onset 12-72h (up to 3-5d).

Lubricant

Coat feces; onset 6-8h oral, 5-15m rectal.

Saline

Draw water into intestine; onset 30m-6h oral, 2-15m rectal.

Hyperosmotic

Osmotic effect; onset 24-72h oral (up to 96h), 15-30m rectal.

Stimulant

Irritate mucosa, increase motility; onset 6-10h oral, 15-60m rectal, 2-6h castor oil.

Nonpharmacologic therapy for constipation

Increase dietary fiber (25g/day women, 38g/day men), increase fluids (2L/day), aerobic exercise, behavior modification (don't ignore urge), proper squatting position.

ORS

Oral Rehydration Solutions for replacing fluids/electrolytes.

Self-care for diarrhea

Uncomplicated acute diarrhea without exclusions.

Referral criteria for diarrhea

Fever >102.2°F, blood/mucus/pus in stool, persistent vomiting, severe dehydration, abdominal pain, <6 months, pregnancy, frail elderly, diabetes, renal disease, immunosuppression, chronic/persistent diarrhea, poor ORS response.

Loperamide

Initial 4mg, then 2mg after each stool; max 8mg/day OTC; avoid in children <6, C. diff, invasive bacterial diarrhea.

Bismuth subsalicylate

Avoid in children <12, pregnant women, and aspirin allergy; may cause tinnitus, black tongue/stool; overdose = neurotoxicity; interacts with warfarin, methotrexate, tetracycline, ciprofloxacin.

OTC diarrhea medications counseling points

Key counseling points about OTC diarrhea medications.

OTC hemorrhoid medications counseling points

Clean and dry area before application, apply thin covering externally, use applicator for internal use, don't exceed daily dose, wash hands before/after.

Self-care for hemorrhoids

Itching, discomfort, irritation, burning, inflammation, swelling.

Referral criteria for hemorrhoids

Severe pain, bleeding, seepage, prolapse, thrombosis, black stools, moderate-severe itching/swelling, or no improvement after 7 days.

Nonpharmacologic therapy for hemorrhoids

Increase fiber, avoid irritating foods, maintain hydration, hygiene, avoid lifting heavy objects, avoid NSAIDs/ASA, use sitz baths.

Internal hemorrhoid products

Anesthetics, vasoconstrictors, protectants, astringents, keratolytics, corticosteroids.

External hemorrhoid products

All internal products plus analgesics/anesthetics/antipruritics.

Simethicone

Safe in all ages.

α-galactosidase

Taken with first bite of food; avoid in galactosemia.

Lactase

Taken with first bite of food for lactose intolerance.

Activated charcoal

Not FDA-approved.

Self-care criteria for gas

Occasional, mild gas.

Referral criteria for gas

Severe/persistent symptoms, sudden change in bowel habits, GI bleeding, fatigue, weight loss, nocturnal symptoms, new onset ≥40 years.

Nonpharmacologic therapy for gas

Eat slowly, avoid carbonated beverages, avoid tight clothes, exercise, avoid lying down after eating, track trigger foods, avoid gum and smoking.

Self-care criteria for nausea and vomiting

Mild motion sickness, overeating, viral gastroenteritis.

Referral criteria for nausea and vomiting

Severe dehydration, pregnancy with severe N/V, infants <2yo, blood in vomit, CNS disease, diabetes with ketones, food poisoning >24h, persistent symptoms.

Nonpharmacologic therapy for motion sickness

Avoid reading, sit in least motion areas, avoid odors, avoid food/alcohol before travel.

Nonpharmacologic therapy for pregnancy-related nausea

Crackers before rising, small meals q1-2h, avoid heat, avoid iron supplements, fresh air.

Antihistamines for nausea and vomiting

Dimenhydrinate, diphenhydramine, meclizine; cause drowsiness, dizziness, anticholinergic effects; avoid in lactation and elderly.

Motion sickness treatments

Antihistamines (meclizine, dimenhydrinate, diphenhydramine).

Pregnancy nausea treatments

Pyridoxine ± doxylamine, ginger, acupressure.

Food/overeating nausea treatments

Antacids, H2RAs, BSS, PCS (Emetrol).

Antacids for heartburn

Fast but short-acting, separate from meds, side effects vary by ingredient.

H2RAs for heartburn

Slower onset, longer relief, prevent if taken before meals.

PPIs for heartburn

Slowest onset, best for frequent heartburn, max 14 days OTC.

Self-care criteria for heartburn

Mild, infrequent symptoms.

Referral criteria for heartburn

Heartburn >3 months, persistent despite treatment, severe symptoms, GI bleeding, unexplained weight loss, nocturnal heartburn, children <2 (antacids), <12 (H2RAs), <18 (PPIs), adults >45 with new symptoms.

Nonpharmacologic therapy for heartburn

Weight loss, avoid triggers, don't eat 2-3h before bedtime, sleep on left side, elevate head of bed, Mediterranean diet, quit smoking.

Heartburn treatments

Antacids or H2RAs for mild/infrequent heartburn, PPIs for frequent symptoms (≥2d/wk).