Interacting drugs - summary

Antacids +

 Ticlopodine 

  Antacids resulted in decrease in ticlopidine plasma levels

 Quinidine  

 Antacids may increase serum quinidine levels, resulting in toxicity

Allopurinol   

Pharmacologic effects of allopurinol decreased

Gabapentin 

  Antacids reduced the bioavailability of gabapentin 

Levodopa    

 Bioavailabilty of Levodopa increased, increased efficacy

 Fluroquinolones 

 Interference with GI absorption of fluoroquinolones decreased serum level Avoid simulataneous use. 

Tetracycline  

Impair absorption of tetracyclines-formation of poorly soluble chelate

Azithromycin  

Aluminium and magnesium -containing antacids reduce peak serum levels

 Dirithromycin  

  When given immediately, absorption of dirithromycin is enhanced

 Ketoconazole  

 Increased gastric pH decreased Ketoconazole absorption

 Zalcitabine    

  Zalcitabine absorption moderately reduced. Do not ingest simultaneously

 Alendronate  

 Pproducts with calcium and multi-valent cations interfere with alendronate

 Sucralfate 

  Total body burden of aluminium may be increased

  Mycophenolate

  Absorption decreased when coadministered with aluminium/magnesium hydrox antacid.    Avoid simultaneous administration 

  Magnesium Salts +

 Aminoquinolines 

  Aabsoption and therapeutic effect of aminoquinolines decreased

  Digoxin    

  Magnesium salts may absorb Digoxin decreasing its bioavailab.

 Nitrofurantoin 

  Adsorption of Nitrofurantoin onto Magnesium salts may occur

 Penicillamine 

 GI absorption of Penicillamine decreased,decreased pharmacologic effect

 Tetracyclines 

  GI absorption and serum levels of Tetracycline decreased

 Vitamin D    

  Hypermagnesemia develop in patients on chronic renal dialysis.

Symptomatic relief of upset stomach with hyperacidity,acidity associated with peptic ulcer,gastritis

Hiatal hernia

Magnesium containing antacids-

Laxative effect as saline cathartic, may cause diarrhea, hypermagnesemia,in renal failure patients

Aluminium containing antacids-

Constipation ( may lead to intestinal obstruction) aluminium intoxification, osteomalacia, and hypophosphatemia, accumulation of aluminium in serum , bone, and the CNS (aluminium accumulation may be neurotoxic) encephalopathy Antacids-

Dose dependent rebound hyperacidity and milk-alkali syndrome

Renal failure(except for control of hyperphosphateaemia) partial intestinal obstruction.

Special precautions-

GI haemorrhage- use aluminium hydroxide with care in patients who have recently suffered massive upper GI hemorrhage ..

Buffer aspirin solutions- caution against use of these antacid/analgesic combination in chronic pain syndrome.

Alkalinization of urine accelrates aspirin excretion and systemic alkalosis and increased sodium load may occur.

Warnings-  Sodium content of antacids may be significant.

Patients with hypertension, congestive heart failure, marked renal failure or on restricterd diet or low-sodium salts should use a low sodium preparation.

Acid rebound- Antacids may cause dose related rebound hyperacidity since they may increase gastric secretion or serum gastric levels.

Milk-alkali syndrome- an acute illness with symptoms of headache, nausea, irritability and weakness, or a chronic illness with alkalosis , hypercalcemia, and possibly renal impairment has ocurred, following concurrent use of high-dose calcium carbonate and sodium bicarbonate.

Hypophosphatemia- prolonged use of aluminium containing antacids may result in hypophosphatemia in normophosphatemic patients if phosphate intake is not adequate. In its more severe forms hypophosphatemia can lead to anorexia, malaise, muscle weakmess, and osteomalacia

Renal function impairment- Use magnesium containing antacids with caution. Prolonged use of aluminium containing antacids in patients with renal failure may worsen dialysis .

Pregnancy- a pregnant women should consult a physician before using an antacid

Indications:

Symptomatic relief of upset stomach with hyperacidity,acidity associated with peptic ulcer,gastritis Hiatal hernia

Dosage: 500 to 1800mg 3 times daily,between meals and bed time.

Children: 50 TO 150mg/Kg/24 hours in divided doses every 4 to 6 hours.

Overdosage-

Magnesium salts-

Symptoms Hypermagnesemia following oral ingestion in absence of renal disease is unlikely. It may occur with overdosage.

Symptoms may include- Hypotension, nausea, vomiting, urinary retention,bradycardia, cutaneous vasodilation, ECG changes, hyporelexia, secondary CNS depression, respiratory changes, coma, asytolic arrest

Treatment

1.Reversal of toxicity is immediate but transient.

2. Dialysis is the treatment of choice ( both peritoneal and hemodialysis )

Missed dose-

1. If your doctor has told you to take this medicine on a regular schedule and you miss a dose. Take it as soon as possible

2. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule.

3. Do not double doses.

Aluminium containing antacids-
Constipation ( may lead to intestinal obstruction) aluminium intoxification, osteomalacia, and
hypophosphatemia, accumulation of aluminium in serum , bone, and the CNS (aluminium
accumulation may be neurotoxic) encephalopathy

Antacids- Dose dependent rebound hyperacidity and milk-alkali syndrome

As per US FDA guidelines as per USPDA 1997

It is the intention to bring out the salient features. Hence relevent details as prescribed by US FDA guidelines as per USPDA 1997  are brought out clearly in the following chapters. 

Descriptons are detailed only to the Group Head and the indiviual items can be seen by visiting the Web Site 

ANTACIDS-

  Antacids are taken by mouth to relieve heartburn, sour stomach, or acid indigestion. They work by neutralising excess acid. Some antacid combinations also contain simethicone which may relieve the symptoms of excess gas

Antacids alone or in combinations with simethicone may also be used to treat the symptoms of stomach or duodenal ulcers

This information applies to the following medicines-

1.Aluminium Hydroxide,Bismuth Subsalicylate, Calcium Carbonate,Famotidine,Magaldrate, Magnesium Hydroxide,Sodium Bicarbonate                         

Aluminium Hydroxide                

General Information

1.Chew tablets throughly before swallowing,follow it with a glass of water

2.Ulcer patients should adhere strictly to prescribed drug schedule

3.Antacids may impair the absorption of many drugs. Do not take other oral drugs within 1 or 2 hours of antacid administration.

3.Magnesium- containing products have a laxative effect and may cause diarrhoea. Aluminium and calcium containing products may cause constipation

4.Inform your doctor,if relief is not obtained or if there are any symptoms that suggest bleeding, such as black tarry stools or coffee ground vomitus.

5. Allergies- Tell your doctor if you are allergic to any other substances such as foods, preservatives or dyes.

6. Diet- Make sure that your doctor knows if you are on a low sodium diet. Some antacids contain large amounts of sodium.

7. Pregnancy- There have been reports of antacids causing side efects in babies whose mothers took antacids for a long time especially in high doses during pregnancy. Also sodium containing medicines should be avoided if you to tend to retain body water.

8. Breast feeding- some aluminium, calcium or magnesium containing products may pass into breast milk. However, these medicines have not been reported to cause problems in nursing babies.

9. Children- anatcids should not be given to children (under 6 years of age) unless ordered by the doctor.

10. Elderly- aluminium containing products should not be used in elderly persons with bone problems or with Alzeheimers disease.

11. Other medicines- When your are taking antacids it is important that your doctor knows thaty ou are taking any other medicines.

12. Tell your doctor if you have any other medical problems, to avoid any ill effects.

13. Dosage- Dose of antacids will be different for different patients. Follow your doctors orders.

14. Missed dose-

Follow the medicine as given by the doctor. If you miss a dose take it as soon as possible. Hoever if it is time for the next dose, skip the mised dose and go back to your regular schedule.

Do not double doses. 

15. Take with or without food

Pharmacology:

Antacids neutralise or reduce gastric acidity,resulting in an increase in pH of the stomach and duodenum. Also, by increasing the gastric pH above 4, they inhibit the proteolytic activity of pepsin.

Antacids do not coat the mucosal lining,but have a local astringent effect.

Take with or without food

Pregnancy:

A pregnant woman should consult a physician before using an antacid.