Calcium salts, drug interactions

There are problems as well in the absorption of certain drugs in the presence of specific food components. L-Dopa absorption may be inhibited in the presence of certain amino acids formed from the digestion of proteins [43], The absorption of tetracycline is reduced by calcium salts present in dairy foods and by several other cations, including magnesium and aluminum [115-117], which are often present in antacid preparations. In addition, iron and zinc have been shown to reduce tetracycline absorption [118], Figure 17 illustrates several of these interactions. These cations react with tetracycline to form a water-in-soluble and nonabsorbable complex. Obviously, these offending materials should not be co-administered with tetracycline antibiotics. 

Secondary> hyperparathyroidism 30 mg PO daily Parathyroid carcinoma 30 mg PO bid titrate q2—4wk based on Ca PTH levels swallow whole take w/ food Caution [C, /—] w/ Szs Disp Tabs SE N/V/D, myalgia, dizziness, 4- Ca2+ Interactions T Effects W/ CYP3A4 inhibitors such as ketoconazole, itraconazole, erythromycin T effects OF drugs metabolized at CYP2D6 such as TCA, thioridazine, flecainide, vinblastine EMS Monitor ECG for signs of hypocalcemia (T QT interval) OD May cause severe hypocalcemia calcium salts can be given... 

Tetracyclines and Metals. Tetracyclines can combine with metal ions, such as calcium, magnesium, aluminum, and iron, in the GI tract to form complexes that are poorly absorbed. Thus, the simultaneous administration of certain drugs (e.g., antacids, iron preparations, products containing calcium salts) by patients on tetracycline therapy could result in a significant decrease in the amount of antibiotic absorbed. When two drugs are recognized as having a potential to interact, there is sometimes a tendency to believe that one of them should be discontinued. In the case of the tetracycline antacid interactions, problems can be... 

Drug-drug iuteractions Calcium salts A previous warning from the FDA that ceftriaxone and intravenous calcium products should not be co-administered to any patient to prevent precipitation leading to end-organ damage [SEDA-33, 494] was retracted in April 2009. In a search of the FDA Adverse Event Reporting System for reports of ceftriaxone-calcium interactions that resulted in serious adverse events, with ceftazidime-calcium as a comparator, 104 and 99 events respectively were identified [23 ]. For ceftriaxone-calcium-related adverse events, 7.7% and 20% were classified as probable and possible respectively for embolism. Ceftazidime-calcium resulted in fewer probable embolic events (4%) but more possible embolic events (30%). The authors claimed that their analysis supported the revised FDA recommendation that patients over 28 days old may receive ceftriaxone and calcium sequentially. This has been supported by the results of a matched cohort study in 142 patients who were exposed to the combination of ceftriaxone and intravenous calcium and in whom mortality and other adverse outcomes were not increased... 

Reduced absorption due to complex formation or other interactions between drugs and intestinal components leading to poor absorption has been described in a few cases. One example is the precipitation of cationic drugs as very poorly-soluble salts with bile acids, which has been reported for several compounds [62], Another well-known example is the complex formation between tetracycline together with calcium due to chelation after administration of the drug together... 

Drugs that may interact with nalidixic acid include theophylline, caffeine, oral anticoagulants, bacteriostatic agents, probenecid, antacids (containing magnesium, aluminum, and calcium), sucralfate, iron salts, multivitamins containing zinc, didanosine, antiarrhythmic agents, and melphalan. 

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