Monday, August 18, 2008

21 - antacids - drug interactions

Examples of antacids (brand names may vary in different countries).

  • Aluminium hydroxide (Amphojel, AlternaGEL)
  • Magnesium hydroxide (Phillips’ Milk of Magnesia)
  • Aluminum hydroxide with magnesium hydroxide (Maalox, Mylanta)
  • Aluminum carbonate gel (Basaljel)
  • Calcium carbonate (Alcalak, TUMS, Quick-Eze, Rennie, Titralac, Rolaids)
  • Sodium bicarbonate (Bicarbonate of soda, Alka-Seltzer)
  • Hydrotalcite (Mg6Al2(CO3)(OH)16 · 4(H2O); Talcid)
  • Bismuth subsalicylate (Pepto-Bismol)
  • Magaldrate with Simethicone (Pepsil)

1.Sparfloxacin is a broad-spectrum oral fluoroquinolone antimicrobial agent with a long elimination half-life. Concurrent treatment with antacids has demonstrated a reduction in the oral absorption of many quinolones.

2.Antacids may reduce zinc and iron absorption due to the inhibition of gastric acid secretion.

3.Possible effects of antacids and acid-lowering drugs on the pH of the proximal small intestine. Both cimetidine and an antacid containing aluminum and magnesium hydroxide reduced folate absorption from a liquid formula meal. Although the effects of these drugs on reducing folic acid absorption were relatively small, such reductions could become clinically significant in chronic antacid or H2 receptor antagonist use or intensive antacid or H2 receptor antagonist use by individuals eating diets that are marginal in folate content.

4.The effect of small doses of four commercially available aluminum-containing antacids on calcium and phosphorus metabolism was investigated in adult males in 20 studies. During the use of these doses of antacids, urinary and fecal calcium increased significantly during a low calcium intake averaging 252 mg/day, and the calcium balances became distinctly more negative. There was a reversal of the normal pattern of phosphorus excretions, namely, the fecal phosphorus was high and the urinary phosphorus was low. During a normal calcium intake of 800 mg/day, these doses of antacids did not result in significant changes of the calcium excretions or balance. In three patients who received large therapeutic doses of antacids, 240 to 450 ml/day, the changes of calcium and phosphorus metabolism were intensified.

5.Following all doses of antacid, a significant increase in 24 h urinary excretion of aluminium was seen. The estimated absorption of aluminium was 8 and 50 times higher when antacids were taken with orange juice or with citric acid, respectively, than when taken with water. Thus, measurable quantities of aluminium are absorbed from single oral doses of antacids. The absorption is substantially enhanced by concomitant ingestion of citric acid.

6.Two infants presented with growth failure and were found to have generalized osteomalacia (rickets) due to phosphate depletion from prolonged administration of an aluminum-containing antacid given for the symptoms of colic. One of the infants developed bilateral proptosis due to craniosynostosis related to the underlying metabolic bone disease. The chronic use of aluminum-containing antacids in infants has potential risk for the growing skeleton and is not innocuous. Therefore, antacid therapy should be used in low doses and very cautiously, with routine monitoring of serum calcium and phosphorus in children taking medications which reduce gastrointestinal phosphate absorption.

7.antacids reduce the absorption of tetracyclines from the gut .

20 - gynaecomastia causing drugs

MCQ: gynecomastia is caused by

  1. rifampicin
  2. spironolactone
  3. thiazide
  4. propranolol

answer: b . spironolactone .

DRUGS CAUSING GYNAECOMASTIA

  1. spironolactone
  2. ketoconazole
  3. estrogens
  4. testosterone
  5. digitalis
  6. clomiphene
  7. phenytoin
  8. griseofulvin
  9. calcium channel antagonists
  10. reserpine
  11. isoniazid
  12. methyldopa
  13. ethionamide

for last seven drugs try this mnemonic : PG CRIME . for the first six drugs try TC DESK .

19 - drugs causing interstitial nephritis

  1. MCQ: drug induced interstitial nephritis is caused by ?

  2. methicillin
  3. cloxacillin
  4. azlocillin
  5. piperacillin

answer: a . methicillin .


drugs causing interstitial nephritis :


  1. pencillins especially methicillin

  1. cephalosporins

  1. ciprofloxacins

  1. NSAIDS

  1. sulfonamides

  1. thiazides

  1. furosemide

  1. rifampicin

  1. phenindone

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