chia jia yanu062203h lee dang niu051984h lim chai yingu062410n lim ren hannu062774h
TRANSCRIPT
CHEMISTRY OF ANTACIDS
Chia Jia Yan U062203HLee Dang Ni U051984HLim Chai Ying U062410NLim Ren Hann U062774H
Content Introduction to gastric juice Types of antacids 3 common types of antacids Usage and treatment Reaction & Mode of action Side effects Limitations Combination Drugs Conclusion
Introduction 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
Gastric Juice
Parietal cell produce gastric acid using proton pump H+/K+ ATPase, an enzyme.
As a proton pump, it transport 1 H+ in exchange of 1 K+ from stomach against concentration gradient with ATP providing the energy.
Epithelial cells
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)
Antacids 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
Types of Antacids Active ingredient: Basic metal salt
Cations used are highlighted in Red Anions used: OH-, O2-, CO3
2-, HCO3-, HPO3
-, Trisilicate (Mg), amino acetate (Al)
Types of Antacids Commonly used: Al(OH)3, MgOH, CaCO3
By mixing and matching cations and anions, combiningdifferent types of antacids, unique attributes, properties
andpotency 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
Magnesium Salts
Aluminium Salts (usually
hydroxide) Alka-mints tablets Childrens’ Mylanta
Tablet Chooz Gum Alcalak Titralac
Milk of Magnesia Philips Tablets Philips Oral
Suspension
Maalox Mylanta ALternaGEL
Most potent antacid ingredient; acts rapidly with more prolonged action than sodium bicarbonate
• Less potent that Ca
• Slow acting• Can use
hydroxide, phosphate & trisilicate (common in Singapore)
Mild and slow acting antacid, last longer
Most stable form of aluminium salts under normal conditions
3 Common Antacids
Calcium Carbonate
Magnesium Salts
Aluminium Salts (usually
hydroxide) Fast acting and long
lasting effect Good when patient
suffers from calcium deficiency
hydroxide has the highest potency
Magnesium antacids are generally NOT absorbed. Any small amounts are cleared renally
May be dehydrated to form powder that readily dissolves in acids
Insoluble in water and forms a suspension/gel that coats and protects the stomach lining
Most appropriate if patient suffers from renal failure
3 Common Antacids
Usage and Treatments Antacids can treats: Esophageal reflux / Heartburn – liquid preferred Gastric & Peptic Ulcer – relief pain while body heals Renal Stones – Al used to remove phosphate stone Constipation – Mg antacids given
Patients suffering from Kidney failure/ uremic patient – only Al antacids allowed
Calcium not given in Singapore
Infants & Elderly not advised to take antacids
Reactions 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 > Mg(OH)2 > Al(OH)3
Reactions - Ca CaCO3 + 2 HCl CaCl2 + H2O + CO2
1g will neutralize 20mEq of acid
CaCl2 + CO32- CaCO3 + Cl- (higher pH in
intestine)
Some unchange calcium is absorbed by the gut, which can raise the pH of the blood causing alkalosis – can affect proteins
Calcium is then removed through the renal system
Reactions - Mg
Magnesium oxides, hydroxides and carbonates are poorly soluble, only Chloride are soluble.
Mg(OH)2 + 2HCl MgCl2 + 2H2O
1 g can neutralize 2.7 mEq of acid
MgCl + HCO3- MgCO3 + HCl
Although non-absorbable, 5% - 10% of Mg enter systemic circulation which then rapidly removed by kidney
Reactions - Al Al(OH)3 + 3HCl AlCl3 + 3H2O Al(H2O)6
3+
1 g can neutralize 0.4 – 1.8 mEq of acid
Solubility of Al increases as pH decrease, above ph>5 neutralizing effect will stop
Al3+ + PO43- AlPO4 (insoluble)
Inadequate amount of phosphate ions will cause Al3+
to be absorbed
It will rebind back at soft tissue or bones where phosphates are found
Side Effect – Al(OH)3 Causes constipation Relaxation of the gastrointestinal smooth muscle
delay in stomach emptying constipation Form insoluble complex of aluminum phosphate
(AlPO4), which is excreted in the faeces. 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
Side Effect – Mg Salt Causes diarrhea:
1. Mg2+ 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 faeces, stimulating nerves in the intestines.3. Mg2+ also play a role in releasing the peptide hormone cholecystokinin, causing accumulation of water and electrolytes in the intestine and triggering intestinal motility.
Side Effect – Mg Salt Magnesium salts may cause central nervous
depression in the presence of renal insufficiency
Causes hypermagnesia 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
Side Effect – CaCO3 Release of CO2 cause belching, nausea, abdominal distention, and flatulence.
Calcium may induce rebound acid secretion.
Calcium stone (kidney stone) can be formed.
Excess Ca2+ cause hypercalcemia. Not a problem in normal patients. But 3 - 4 g of CaCO3 per day can be problematic in patients with uremia.
Antacids may affect drugs by altering gastric and urinary pH, (e.g., thyroid hormones)
Al3+ and Mg2+ 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
Antacids-Drugs Interaction
Require large neutralizing capacity single dose (156 meq) antacid 1 hr after meal neutralize gastric acid for 2 hr2nd dose 3 hr after eating maintains effect for > 4 hr
Tablet antacids generally weaker large number required
Convenient to administer since it can carried around easilyBut it needs to be chewed properly
Limitation
Simethicone Anti-flatulence drug to ease discomfort Breaking down gas bubbles in stomach
by lowering the surface tension Alginates
React with saliva to form a viscous raft of non-irritating material that floats atop stomach contents. When reflux occurs, refluxate consists of nonirritant materials
Cannot be used with simethicone!
Combination Drugs
H2-Histimine Blockers Inhibit gastric acid secretion
Proton Pump Inhibitors – Omeprezole Best for short-term and long term
treatment of GERD But take long to take effect (approx 1-4
days)
Combination Drugs
Reference WEBSITES Alu-cap, from Net Doctor. Website: http://
www.netdoctor.co.uk/medicines/100000085.html Antacid Medication in Pregnancy May Increase Childhood Asthma, from
Physorg.com. Website: http://www.physorg.com/news150121295.html Antacids, from MedTV. Website: http://
gerd.emedtv.com/antacids/antacids.html Antacids: Facts and Discussion Forum and Encyclopaedia Articles, from
Absolute Astronomy. Website: http://www.absoluteastronomy.com/topics/Antacid
Antacids for GERD, from Quest Diagnostics. Website: http://www.questdiagnostics.com/kbase/topic/detail/drug/hw94857/detail.htm
Antacids, Information about Antacids, from Free Health Encyclopaedia. Website: http://www.faqs.org/health/topics/50/Antacids.html
Antacids: Over-the-counter (OTC) drugs, from Merck Website: http://www.merck.com/mmhe/sec02/ch018/ch018g.html
Antacid | World of Chemistry Summary, from Book Rags. Website: http://www.bookrags.com/research/antacid-woc/
Chemistry 104: Analysis of Antacid Tablet, from Chemistry LA Tech Website: http://www.chem.latech.edu/~deddy/chem104/104Antacid.htm
Reference WEBSITES Information about Antacids, from RXList The Internet Drug Index.
Website: http://www.rxlist.com/script/main/art.asp?articlekey=95545 Magnesium Trisilicate Tablets BP, from Net Doctor. Website: http://
www.netdoctor.co.uk/medicines/100001573.html Minerals ~ Magnesium, from SpringBoard. Website: http://
www.springboard4health.com/notebook/min_magnesium.html PharmGKB: Antacids, from Pharmokogenomics Knowledge Base.
Website: http://www.pharmgkb.org/do/serve?objId=PA452298&objCls=Drug#tabview=tab1
What is Milk of Magnesia?, from Wise Geek. Website: http://www.wisegeek.com/what-is-milk-of-magnesia.htm
BOOKS Haddad L.M., Shannon M.W., Winchester J.F. (1998). Clinical Management
of Poisoning and Drug Overdose Halter, F. (1981). Antacids in the Eighties: Symposium on Antacids,
Hamburg. Munchen: Urban and Swarzenburg Kosegarten D.C., Pisano D.J. Vogenburg F.R. (2000). Mastering
Pharmacy , licensure and certification: A case-based review. New York: McGraw-Hill
Washington Neena. (1992). Antacids and Anti-reflux Agents. CRC Press Stoelting R.K. (2006) Handbook of Pharmacology and Physiology in
Anaesthetic Practice. Philadelphia: Lippincott Williams and Wilkins Van Ness M.M., Gurney M.S., Jones D.M. (1995). Handbook of
Gastrointestinal Drug Therapy. Boston: Little, Brown
Reference