Chapter 57- Antacids Flashcards
Antacids-Generic Medications
Sodium bicarb (Bell-ans)
Calcium carbonate (Osytercal, Tums)
Magnesium salts (Milk of Magnesia)
Aluminum salts (Amphojel)
Antacids-MOA
Antacids neutralize stomach acid by direct chemical reaction.
Antacids-Sodium Bicarb
(oldest drug in this group)
Readily available in many preparations, including baking soda powder, tablets, solutions, and as an injectable for treating systemic acidosis.
This drug is widely distributed when absorbed orally, reaching peak levels in 1-3hr, crossing the placenta, and entering breast milk.
Excreted in the urine
Can cause serious electrolyte imbalance in people with renal impairment
Antacids-Calcium carbonate
Precipitated chalk and is available in tablet and powder forms
The main drawbacks are constipation and acid rebound.
Onset of action is about 3-5min
It can be absorbed systemically and cause calcium imbalance
When absorbed, it is metabolized in the liver
Excreted in the urine and feces
Known to cross the placenta and enter breast milk
Antacids-Magnesium salts
Effective in buffering acid in the stomach but have been known to cause diarrhea; sometimes used as laxatives.
Available as tablets, chewable, tablets, capsules, and liquid forms.
Although not absorbed systemically, magnesium can lead to nerve damage and even coma if absorbed systemically
Excreted in the feces, but excreted in the urine if absorbed systemically.
Antacids-Aluminum salts
Available as tablets, capsules, suspensions, and liquid form.
Do not cause acid rebound but are not very effective in neutralizing acid.
Bound in the feces for excretion
Related to severe constipation
Binds dietary phosphates and causes hypophosphatemia, which can then cause a calcium imbalance throughout the system.
Antacids-Contraindications & cautions
Caution should be used in the following instances:
Any condition that can be exacerbated by electrolyte or acid-base imbalance
GI obstruction- Could cause systemic absorption of the drug
Renal dysfunction
Pregnancy and lactation
Antacids-Adverse effects
Frequent administration can cause acid rebound, in which the stomach produces more acid in response to the alkaline environment
In many cases, acid rebound causes an increase in symptoms, which results in an increased intake of the antacid. The more frequent administration, the higher the incidence of systemic effects. Alkalosis with resultant metabolic changes (N/V, neuromuscular changes, headache, irritability, muscle twitching, and even coma) may occur.
Calcium salts may lead to hypercalcemia and milk-alkali syndrome (seen as alkalosis, renal calcium deposits, or severe electrolyte disorders)
Constipation or diarrhea may occur depending on the antacid being used
Hypophosphatemia can occur with the use of aluminum salts
Fluid retention and heart failure can occur with sodium bicarb because of the high sodium content.
Antacids-Drug to drug interactions
Because most drugs are prepared for an acidic environment, an alkaline environment can prevent them from being broken down for absorption, or can render them neutralized so they cant be absorbed. Patients taking antacids should take them 2 hr before/after any other medication
If the pH of the urine is affected by large doses of antacids, the levels of drugs such as quinidine may increase and the levels of salicylates may decrease
Sodium Bicarb-Antacid Prototype
Adjunctive treatment of severe diarrhea
Also used for the treatment of metabolic acidosis (IV form)
May also be used to treat certain drug intoxication to minimize the uric acid
crystallization
Adverse effects:
Gastric rupture, systemic alkalosis (headache, nausea, irritability, weakness, tetany, confusion) hypokalemia (secondary to intracellular shifting of potassium, and gastric acid rebound)
Antacids- Pre/post medication assessment
Monitor lab test results, including serum electrolyte levels and renal function
Give 1hr before, or 2hr after any other oral medications
Monitor for S/S of acid-base imbalance or electrolyte imbalance
Monitor for diarrhea or constipation
