AntacidPosted on 28/2/2008

Antacid is a basic chemical compound that used to neutralize gastric acid. Pepsin is a type of enzyme secreted by stomach to digest our food. Antacid used to buffer the gastric acid to pH of 3 or 4 (the pH of the gastric juice is usually 1 or 2). That’s means that antacid interfere with pepsin activities, therefore when the gastric juice is buffered enough then it can  reduce the corrosive effect of gastric acid toward the stomach. Antacid products containing either sodium bicarbonate, aluminium hydroxide, magnesium hydroxide, calcium carbonate, aluminium phosphate, or a combination of these agent.Introduction

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This product is available in the following dosage forms:

  • Granule
  • Suspension
  • Tablet, Chewable
  • Liquid
  • Tablet
  • Capsule, Liquid Filled
  • Capsule
  • Powder for Suspension
  • Powder, Effervescent
  • Tablet, Effervescent
  • Wafer
  • Tablet, Extended Release
  • Solution

The liquid formulation of antacid has more rapid acid-neutralizing action than the tablet form whereas tablet form antacids have to be chewed well to maximize its effect.
Antacid are cleared from the empty stomach in about 30 minutes. However, the presence of food is sufficient to elevate and prolong the neutralizing effects of antacids for about 2-3 hours.


Classification of Antacid
Sodium bicarbonate is a typical systemic antacid. It is readily soluble and absorbed and it has short duration of action. It should be remembered that sodium bicarbonate cannot be over ingest than the usual need to neutralize the gastric acid. When over ingested, it will cause electrolyte imbalance in our body and burden the kidney.

Aluminium hydroxide is a non- systemic antacid. It does not interfere with electrolyte balance and not completely suppress the peptic digestion. However, the formation of hydroxide chloride result of reaction between aluminium hydroxide and hydrochloride acid responsible for the astringent and constipation effect. Besides, it interferes with absorption of phosphate. Aluminium phosphate has similar action with aluminium hydroxide but it does not interfere with phosphate absorption.

Magnesium hydroxide is also a type of non- systemic antacid that interferes with the absorption of folic acid and iron. It may induce diarrhea that causing loss of potassium ion in our body. If not immediately replenish the potassium, muscle cramp may occur.


Precautions and Side Effects

  • Sodium bicarbonate containing antacid that is high content in sodium, is not suitable administered by patient with hypertension, heart problem, liver failure or pregnant woman.
  • Aluminium containing antacid may induce constipation whereas magnesium containing  antacid promote diarrhea, but by combining magnesium and aluminium hydroxide can provide a relative balance and sustained neutralizing capacity and reduce the adverse gastrointestinal effect.
  • Aluminium containing antacid except aluminium phosphate may interfere with any phosphorus absorption, so for patient who has low phosphate intake, may encounter hypophosphatemia if take this antacid.
  • Calcium carbonate containing antacid can neutralize gastric acid rapidly and effectively. However, this compound can release carbon dioxide gas and thus may cause belching, nausea, abdominal distention and flatulence. Some antacid may combine with simethicone; it is useful to prevent flatulence result from the production of carbon dioxide gas. For patients who are potentially predisposed to gastroduodenal ulcer, it is advised that should not use the antacid that containing simethicone and aspirin. These will worse the condition.


Drug Interaction
Antacid interact with:

  • iron supplement
  • tetracycline
  • warfarin
  • digoxin
  • phenytoin
  • quinidine
  • isoniazide
  • ketoconazole
  • fluoroquinolone

As antacid can alter the pH of gastric and urine, it may affect the dissolution, bioavailability and renal elimination of some medicine, such as thyroid hormone, allopurinol, and imidazole antifungal.

Aluminium ion and magnesium ion can chelate other drug present in the gastrointestinal tract and influence the drug absorption. Thus, avoid the concurrent administration of antacid and other medication that can interact with aluminum and magnesium ions. It is advisable to take antacid 2 hours before or after the ingestion of other drugs.


Example of Antacid:
Brand name: Actal
Content: Alexitol sodium equivalent to 216mg of aluminium hydroxide
Dosage: 2 – 4 tablet, repeat as required, taking 1 hours after food
Special precaution: Renal insufficiency,low phosphate diet
Adverse effect: Constipation may occur if use longterm
Drug interaction: May impair absorption of tetracycline

Brand name: Alucid
Content: dimethylpolysiloxane 50 mg, aluminium hydroxide 250 mg, magnesium hydroxide 250 mg
Dosage: Adult and children more than 12 years old: 1-2 tablet. Take before meals and at bedtime or when is required.

Brand name: Dhalumag   DHA
Content: Per 5 ml magnesium trisilicate, aluminium hydroxide 250 mg.
Dosage: 5- 15 ml repeated as required
Special precaution: Renal dysfunction, low phosphate diet.
Adverse effect: Constipation, diarrhea; intestinal obstruction (large dose)
Drug interaction: Alter absorption of tetracycline, isoniazide, iron, quinidine and Warfarin

Brand name: Gerskin
Content: magnesium oxide 200mg, aluminium hydroxide gel 200mg, dimethylpolysiloxane 20 mg
Dosage: adult, 1-2 tablet three to four times a day
Contraindication: Renal failure, severe debilitation
Adverse reaction: Rarely, soft stool, diarrhea, nausea, vomiting, gastralgia, anorexia
Drug interaction: tetracycline, digoxin, vitamin







Brand name: Maalox plus
Content: Per tablet magnesium hydroxide 200mg, dried aluminium hydroxide gel 200 mg, simethicone 25 mg. Per 5 ml suspension magnesium hydroxide 200mg, aluminium hydroxide 225mg, simethicone 25 mg
Dosage: 2-4 tablet four times a day or 2-4 teaspoonful four times a day. Take 20- 60 minutes after meals for tablet it must chew well before swallowed
Contraindication: severe debilitation; kidney failure.
Adverse reaction: GI disturbance (rare)

Other example :Hydrosil, Suntacid, Gelusil,