Antacids: weak bases that react with hydrochloric acid to form salt & water.
o Used in the treatment of Hyperacidity, GERD, PUD, hyperphosphatemia, and calcium deficiency
o Contain combinations of
metallic cation (aluminum, calcium, magnesium, and sodium)
and basic anion (hydroxi...
➢ Antacids: weak bases that react with hydrochloric acid to form salt & water.
o Used in the treatment of Hyperacidity, GERD, PUD, hyperphosphatemia, and calcium deficiency
o Contain combinations of
▪ metallic cation (aluminum, calcium, magnesium, and sodium)
▪ and basic anion (hydroxide, bicarbonate, carbonate, citrate, and trisilicate)
➢ Pharmacodynamics, Pharmacokinetics, Pharmacotherapeutics
o Neutralize Gastric Acidity (causes ^pH of the stomach and duodenal bulb)
o Inhibit proteolytic activity of pepsin
o Increase lower esophageal sphincter tone
o Acid-neutralizing capacity ANC varies between products expressed in mEqs
o If ingested in a fasting state, antacids reduce acidity for approximately 20 to 40 minutes
o If taken 1 hr after a meal, acidity is reduced for 2 to 3 hrs
o A second dose taken after a meal maintains reduced acidity for more than 4 hrs after the meal
o The action of antacids occurs locally in the GI tract with minimal absorption, minimal metabolism
o ALL antacids are contraindicated in the presence of severe abdominal pain of unknown cause, especially if
accompanied by fever
-HIGH SODIUM content: pts w/ HTN, CHF, marked renal failure, or on low-sodium diets need to use low sodium
preparation
-Concurrent administration with enteric-coated drugs, destroys the coating= alters absorption, ^ the risk for
adverse effects
-Administrations should be separated by at least 2 hours to decrease drug/drug interactions
1. Calcium based antacids: TUMS, Caltrate, Calcarb
• Prescribed to treat calcium deficient states, i.e. chronic renal failure, post-menopause, and osteoporosis
• Used to bind phosphates in CRF
• Require Vitamin D for absorption from the GI tract
• Excreted mainly in feces, 20% in urine
• ADR: Contraindicated in the presence of hypercalcemia and renal calculi
• Can cause constipation- increase bulk, fluids and mobility, stool softener
• Administered 30min- 1hr on empty stomach or 3hr after meals
• Should not be administered with food containing large amounts of oxalic acid (spinach, rhubarb), or
phytic acid (bran, cereals), they decrease the absorption of calcium
• Taking w/ foods containing phosphorus (milk, dairy) can lead to milk-alkali syndrome (N/V, confusion,
headache).
• Taking with acidic fruit juice improve absorption
2. Aluminum based: AlternaGEL, Amphojel, Mylanta
• Inhibit smooth muscle contraction and slow gastric emptying
Aluminum is not easily • Used to bind phosphates in CRF
removed by dialysis b/c
it is bound to albumin • Not absorbable with routine use
& transferrin = do not • Aluminum concentrated in the CNS
cross dialysis
membrane • Bind with phosphate and excreted in feces
• Prolonged use in patients with renal failure may result in dialysis osteomalacia
o Aluminum deposits in bone and osteomalacia occurs
• Elevated aluminum tissue levels contribute to the development of dialysis encephalopathy
• Used to treat hyperphosphatemia in pts w/ renal failure & phosphate renal stone prevention
• Can cause constipation- increase bulk, fluids and mobility, stool softener
3. Magnesium based: Milk of mag, Maalox, Mylanta
, • Can be used to treat magnesium deficiencies from malnutrition, alcoholism, or mag-depleting drugs
The malfunctioning • Contraindicated in patients with renal failure & used with caution in pts with renal insufficiency
kidney cannot
excrete • Not absorbable with routine use
magnesium=
hypermagnesemia
• Excreted in the urine
may result • Contraindicated in patients with renal failure, use with caution for patients with any degree of renal
insufficiency
o Malfunctioning kidney is unable to excrete magnesium and hypermagnesemia may result
• Can cause diarrhea- increase fiber intake (Alkalosis may occur in renal impairment)
Clinical Use and Dosing
,➢ Rational drug selection
o ANC, sodium content, and cost
o Combination products with aluminum hydroxide and magnesium hydroxide have the highest ANC (use is
moderate to severe disease
➢ Monitoring
o Serum phosphate, potassium, and calcium during chronic use
o These drugs may cause increased serum calcium and decreased serum phosphate
o Chronic magnesium hydroxide use may cause elevated Mg levels in patients with renal failure or the elderly
with decreased renal function
➢ Patient education
o Take as prescribed, especially related to mealtimes
o Take 1-3 hrs after meals and at bedtime
o Chewable tablets chew thoroughly and drink half a glass of water
o Shake suspensions before administration
o Many drug interactions, separate doses by 2 hours apart
o Calcium based antacids should not be administer with food containing large amounts of oxalic acid (spinach,
rhubarb) or phytic acid (brans, cereals) decrease absorption
o Avoid taking with food containing phosphorus (milk, dairy products) can cause milk-alkali syndrome (NV,
confusion, HA)
o Consult provider: before taking antacids for more than 2 weeks if a problem recurs, if relief is not obtained,
or if symptoms of GI bleeding (black, tarry stools, coffee ground emesis
o Aluminum and calcium antacids may cause constipation: increase bulk, increase fluid intake, and more
mobility, stool softened
o Magnesium antacids may cause diarrhea, increase fiber
o Avoid smoking, avoid flat lying body position while sleeping, foods that irritate the gastric mucosa (spicy
foods), or stimulate acid production (alcohol) and foods that decrease lower esophageal sphincter tone
(caffeine, chocolate, fatty foods)
, ➢ Antidiarrheals:
• Diarrhea that lasts for less than 2 weeks is considered acute; if it lasts more than 2 weeks, it is considered
chronic.
• Pharmacodynamics, Pharmacokinetics
• Three main classes absorbent preparations (kaolin and pectin (Kapectolin) and bismuth subsalicylate (Pepto-
Bismol, Kaopectate Liquid), opiates (diphenoxylate with atropine (Lomotil), diphenoxin with atropine (Motofen),
and loperamide (Imodium)) and anticholinergics (IBD)
• Contraindications: Drugs that decrease gastric motility or delay intestinal transit time have induced toxic
megacolon, especially in those with inflammatory bowel disease
• All antidiarrheals (except Crofelemer) require cautious use in older adults and when there is r/f impaction
• Older adults are especially sensitive to diphenoxylate or difenoxin r/t atropine and anticholinergic properties
• Not recommended for children under 12, none of the antidiarrheals are safe for children under 2 years old
• Antidiarrheals are contraindicated in the Tx of diarrhea in most children
• Standard of care: oral rehydration therapy
• ADRS Rebound constipation is the main adverse effect
-Kaolin-pectin (kapectolin): Acute diarrhea
• Kaolin is a clay-like powder that attracts and holds onto bacteria
• Pectin thickens the stool by absorbing moisture
• Used to treat simple diarrhea
• Act locally in the bowel, not systemically absorbed
• Pregnancy Category B
-Bismuth subsalicylate (Pepto bismol): Acute diarrhea, travelers’ diarrhea
▪ Antisecretory and antimicrobial effects
▪ Also used as part of a multidrug regimen for H. pylori
▪ Undergoes chemical dissociation in GI, salicylate moiety is absorbed
▪ Salicylate is metabolized in the liver and more than 90% is excreted in urine
▪ Contraindicated in children or teenagers during or after recovery from chickenpox or flu-like illness
▪ Contraindicated for patients with ASA hypersensitivity
▪ For bismuth subsalicylate, additional reactions that all patients should be warned about are gray/black
stools and black tongue, the results of the bismuth. Patients should be told to expect this reaction and
that it does not indicate GI bleeding.
▪ Bismuth subsalicylate may potentiate the risk for toxicity if taken w/ aspirin
▪ R/f hypoglycemia in large doses with insulin or oral hypoglycemics
-Crofelemer (fulyzaq): Symptomatic relief of noninfectious diarrhea in adult pts w/ HIV/AIDS on antiretroviral therapy
▪ Botanical blocking chloride secretion from the epithelial cells in the intestinal lumen, decreasing water loss
and normalizing the flow of chloride and water in the intestinal tract
▪ Minimal absorption after PO administration
▪ Metabolism and excretion are not known
▪ In clinical trials more likely to have URI, bronchitis, and cough than placebo group
▪ Adverse GI effects flatulence, increased bilirubin, and nausea
-diphenoxylate w/atropine (Lomotil): Acute diarrhea
▪ Constipating meperidine congener, lacks analgesic activity
▪ At high doses can produce euphoria and physical dependence
▪ Anticholinergics are useful only with inflammatory bowel disease
▪ Well absorbed from GI tract
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