Antacids: weak bases that react with hydrochloric acid to form salt & water.
o Used in the treatment of Hyperacidity, GERD, PUD, hyperphosphatemia,
... [Show More] 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
Used to bind phosphates in CRF
Not absorbable with routine use
Aluminum concentrated in the CNS
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 [Show Less]