Antacids tables

Antacids continue to be used by patients for a variety of indications. Many factors, including palata-bility, determine the effectiveness and choice of antacid (Table 36-1). Although sodium bicarbonate effectively neutralizes acid, it is very water-soluble and rapidly absorbed from the stomach, and the alkali and sodium loads may pose a risk for patients with cardiac or renal failure. Depending on particle size and crystal structure, CaCO rapidly and effectively neutralizes gastric H+, but the release of COj from bicarbonate- and carbonate-containing antacids can cause belching, nausea, abdominal distention, and flatulence. Calcium also may induce rebound acid secretion, necessitating more frequent administration. 

USP-grade anhydrous magnesium carbonate is used as a flavor impression intensification vehicle in the processed food industry (see Flavors and spices). Basic magnesium carbonates are used as free flowing agents in the manufacture of table salt, as a hulking agent in powder and tablet pharmaceutical formulations, as an antacid, and in a variety of personal care products (see Pharmaceuticals). 

If antacids fail to improve symptoms, recommend ranitidine (Table 44—5). Although most H2 blockers are thought to be safe in pregnancy, ranitidine is the only agent with double-blind, randomized trials evaluating its use in this population.23... 

Table III. Effect of Small and Large Doses of Aluminum-Containing Antacids on Calcium Metabolism...

Deravirdine (Rescnptor) [Antiretroviral/NNRTI] Uses HIV Infxn Action Nonnucleoside RT inhibitor Dose 400 mg PO tid Caution [C, ] CDC recommends HIV-infected mothers not to breast-feed (transmission risk) w/ renal/hepatic impair Contra Use w/ drugs dependent on CYP3A for clearance (Table VI-8) Disp Tabs SE Fat redistribution, immune reconstitution synd, HA, fatigue, rash, T transaminases, N/V/D Interactions T Effects W/ fluoxetine T effects OF benzodiazepines, cisapride, clarithromycin, dapsone, ergotamine, indinavir, lovastatin, midazolam, nifedipine, quinidine, ritonavir, simvastatin, terfena-dine, triazolam, warfarin effects W/ antacids, barbiturates, carbamazepine, cimetidine, famotidine, lansoprazole, nizatidine, phenobarbital, phenytoin, ranitidine, rifabutin, rifampin effects OF didanosine EMS Use of benzodiazepines and CCBs should be avoided may cause a widespread rash located on upper body and arms OD May cause an extension of nl SEs symptomatic and supportive Deferasirox (Exjade) [Iron Chelator] Uses Chronic iron overload d/t transfusion in pts >2 y Action Oral iron chelator Dose Initial 20 mg/kg... 

Steroids, Systemic, Tables VI-1 and VI-2 Interactions T Effects Wf cyclosporine, estrogens, OCPs, macrolides T effects OF cyclosporine T effects W/ aminog-lutethimide, antacids, barbiturates, carbamazepine, cholestyramine, colestipol. 

Prednisolone [Corticosteroid] [See Steroids and Table VI-1] Interactions T Effects W/ clarithromycin, erythromycin, estrogen, ketoconazole, OCPs, troleandomycin X effects W/ antacids, aminoglutethimide, barbiturates, cholestyramine, colestipol, phenytoin, rifampin X effects OF anticoagulants, hypoglycemics, INH, salicylates, vaccine toxoids EMS Infxns may be masked OD May cause wt gain, T hair growth, acne, HTN, peripheral edema, and sore muscles symptomatic and supportive... 

Absorption of drugs, which occurs mainly via passive diffusion, changes little with advancing age. The changes listed in Table 1 could potentially affect drug absorption. More important changes result from the concurrent administration of several medications. For example, antacids decrease the oral absorption of cimet-idine, and alcohol accelerates the absorption of chloral hydrate. 

The reactions in Table 13.8 show that carbon dioxide is a common product in many neutralization reactions. This is clearly displayed when a drop of vinegar (acetic acid) is added to baking soda (sodium bicarbonate). Some aspirin includes an antacid in their formulation to neutralize some of the acidity imparted by the aspirin (acetylsalicylic acid). These are commonly referred to as buffered aspirins. 

Histamine H2-receptor antagonists are well absorbed orally, although concurrent antacid therapy may reduce bioavailability by up to 30%. They are widely distributed in the body, crossing the blood-brain barrier and the placenta. Cimetidine, ranitidine and famotidine are extensively metabolised in the liver, and about one-third excreted unchanged in urine, while only one-third of nizatidine is metabolised (Table 11.1). Elimination half-life is increased up to tenfold in renal failure, and doses must be adjusted. 

Adsorbents used to treat diarrhea are listed in Table 27-3. These agents frequently appear as the active ingredients in over-the-counter products and may be combined with each other or with other drugs such as antacids. 

Delavirdine is extensively metabolized to inactive metabolites by the CYP3A and CYP2D6 enzymes. However, it also inhibits CYP3 A and thus inhibits its own metabolism. In addition to its interactions with other antiretroviral agents (see Table 49 1), delavirdine will result in increased levels of numerous agents (Table 49-3). Dose reduction of indinavir and saquinavir should be considered if they are administered concurrently with delavirdine. Delavirdine plasma concentrations are reduced in the presence of antacids, phenytoin, phenobarbital, carbamazepine, rifabutin, and rifampin concentrations are increased during coadministration with clarithromycin, fluoxetine, dexamethasone, and ketoconazole. 

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