Chia Jia Yan Lee Dang Ni U062203H U051984H Lim Chai Ying U062410N Lim Ren Hann U062774H

       Introduction Types of antacids Usage and treatment Mode of action & reaction Side effects Combination Drugs Conclusion

 Stomach contains gastric acid of pH of 2 to 3.

 Gastric acid contains HCl, KCl and NaCl.

 Excess acid can cause pH to fall below 2 which can cause problems such as abdominal pain and heartburn etc.

 Gastric juice activates pepsin, an enzyme that carries out proteolysis – break down proteins by breaking bonds that links amino acids

Epithelial cells

Parietal cell produce gastric acid using proton pump H + /K + ATPase, an enzyme.

As a proton pump, it transport 1 H exchange of 1 K + concentration gradient with ATP providing the energy.

+ in from stomach against Picture taken from My Optum Health. http://www.myoptumhealth.com/portal/DiseasesandConditions/item/Gastroesophageal+reflux+disease+and +hea?section=2 (accessed on 8 April 2009)

     Alkaline salt or buffer substances used to neutralize stomach acid and bring its pH back to 2 to 3 Treat indigestion or relieve any discomfort caused by acidity of stomach acid Reduces acid concentration within the lumen of the esophagus which increase the intra-esophageal pH and decrease pepsin activity In forms of tablet, liquid suspension , lonzenges, chewing gum, dissolving tablet Liquid relief symptoms faster

 Active ingredient: Basic metal salt  Cations used are highlighted in Red Anions used: OH , O 2 , CO 3 2 , HCO 3 , HPO 3 , Trisilicate (Mg), amino acetate (Al)

 Commonly used: Al(OH) 3 , MgOH, CaCO 3 By mixing and matching cations and anions, combining different types of antacids, unique attributes, properties and potency of antacids are created. Either Mixture or Complex antacids

Other common ingredient:

  Simethicone – relieve gas by breaking down bubbles Alginic acid – foaming agent that floats on top of stomach content

  

Calcium Carbonate

Most potent antacid ingredient; acts rapidly with more prolonged action than sodium bicarbonate Fast acting and long lasting effect Good when patient suffers from calcium deficiency     

Magnesium Salts

Can use hydroxide, phosphate and trisilicate

(common in Singapore)

 Less potent that Ca hydroxide has the

Aluminium Salts



(usually hydroxide)

Most stable form of aluminium salts under normal conditions May be dehydrated to form powder that readily dissolves in highest potency Slow acting Magnesium antacids  acids Mild and slow acting antacid, last longer are generally NOT absorbed. Any small  Insoluble in water and forms a amounts are cleared renally  suspension/gel that coats and protects the stomach lining Most appropriate if patient suffers from

Calcium Carbonate

     Alka-mints tablets Childrens ’ Mylanta Tablet Chooz Gum Alcalak Titralac   

Magnesium Salts

Milk of Magnesia Philips Tablets Philips Oral Suspension   

Aluminium Salts (usually hydroxide)

Maalox Mylanta ALternaGEL

 Antacids needs to be in hydrated form for better neutralizing effect Aluminium Antacids  Aluminium based antacids preferred for kidney failure patient as it can be used to remove excess phosphate ions  Other usage: Magnesium used as a laxative for constipated patient

 Strength of an antacid to neutralize acid in the stomach is determined using the antacid’s neutralizing capacity (ANC)  ANC is expressed as milliequivalents (mEq) of the amount of 1N HCl that can be neutralized  FDA: all antacids must have a neutralizing capacity of at least 5 mEq per dose.  The commonly used antacids are ranked in this order with respect to ANC, from strongest to weakest 

CaCO3 > NaHCO3 > Mg(OH)

2

> Al(OH)

3

   CaCO 3 + 2 HCl  CaCl 2 + H 2 O + CO 2 1g will neutralize 20mEq of acid CaCl 2 + CO 3 2 intestine)  CaCO 3 + Cl (higher pH in Some unchange calcium is absorbed by the gut, which can raise the pH of the blood causing alkalosis – can affect proteins

 Magnesium oxides, hydroxides and carbonates are poorly soluble, only Chloride are soluble.

   Mg(OH) 2 + 2HCl  MgCl 2 + 2H 2 O 1 g can neutralize 2.7 mEq of acid MgCl + HCO 3  MgCO 3 + Although non-absorbable, 5% - 10% of Mg enter systemic circulation which then rapidly removed by kidney

 Al(OH) 3 + 3HCl  AlCl 3 + 3H 2 O Al(H 2 O) 6 3+ 1 g can neutralize 0.4 – 1.8 mEq of acid  Solubility of Al increases as pH decrease

 Complex antacids can be used. E.g. Magaldrate [Mg(OH)Al 2 (OH) 10 ] 4 .2H

2 O

   Causes constipation Relaxation of the gastrointestinal smooth muscle delay in stomach emptying constipation Form insoluble complex of aluminum phosphate (AlPO 4 ), which is excreted in the feces. May lead to lowered serum phosphate concentrations and phosphorus mobilization from the bone. If phosphate depletion is already present, osteomalacia, osteoporosis, and fracture may result BUT it reduce phosphates in the urine and prevent formation of phosphatic (struvite) urinary stones

 Causes diarrhea: 1. Mg 2+ draw water from the surrounding body tissues into the intestinal tract by osmosis.

2. Higher quantity of water in the intestinal tract softens and increases the volume of feces, stimulating nerves in the intestines.

3. Mg 2+ also play a role in releasing the peptide hormone cholecystokinin, causing accumulation of water and electrolytes in the intestine and triggering intestinal motility.

 Magnesium salts may cause central nervous depression in the presence of renal insufficiency  Causes hypermagnesaemia in patients with severe renal function impairment BUT Magnesium hydroxide inhibits the precipitation of calcium oxalate and calcium phosphate, thus preventing the formation of calcium stones

 Release of CO 2 cause belching, nausea, abdominal distention, and flatulence.  Calcium may induce rebound acid secretion.

 Calcium stone (kidney stone) can be formed.

 Excess Ca 2+ cause hypercalcemia. Not a problem in normal patients. But 3 - 4 g of CaCO problematic in patients with uremia.

3 per day can be

 Antacids may affect drugs by altering gastric and urinary pH, (

e.g

., thyroid hormones)  Al 3+ and Mg 2+ antacids are notable for their propensity to chelate other drugs present in the GI tract, forming insoluble complexes that pass through the GI tract without absorption  Most interactions can be avoided by taking antacids 2 hours before or after ingestion of other drugs

 Require large neutralizing capacity single dose (156 meq) antacid 1 hr after meal  gastric acid for 2 hr neutralize 2nd dose 3 hr after eating  maintains effect for > 4 hr  Tablet antacids generally weaker  required large number  Very inconvenient to adminster

  Pictures: http://www.specialtyminerals.com/specialty applications/specialty-markets-for minerals/pharmaceuticals/antacids/  NiDDK Image Library, http://www.catalog.niddk.nih.gov/imagelibrary/d etail.cfm?id=124