Gastrointestinal tract magnesium

Inorganic compounds such as aluminium hydroxide, sodium bicarbonate, and magnesium and calcium carbonates are commonly used as antacids. There is much scope for the redesign of these agents to achieve fine control of local pH values in the gastrointestinal tract via control of the rate of release of the active bases (e.g., from insoluble compounds). 

Administration of activated charcoal as an absorptive surface for di-w-octylphthalate has been suggested (Stutz and Ulin 1992). If ingestion of large amounts of di-/ -octylphthalate has occurred, the administration of a cathartic, such as magnesium sulfate, has been shown to increase the elimination of the substance from the gastrointestinal tract (Stutz and Ulin 1992). 

Absorption from the gastrointestinal tract can be affected by other drugs and by food. Aluminum, calcium, and magnesium ions in antacids or dairy products form insoluble chelates with all tetracyclines and inhibit their absorption. Food inhibits tetracycline absorption but enhances doxycycline absorption food delays but does not diminish metronidazole absorption fatty food enhances griseofulvin absorption. 

These antibiotics are partially absorbed from the stomach and upper gastrointestinal tract. Food impairs absorption of all tetracyclines except doxycycline and minocycline. Absorption of doxycycline and minocy-cbne is improved with food. Since the tetracyclines form insoluble chelates with calcium (such as are found in many antacids), magnesium, and other metal ions, their simultaneous administration with milk (calcium), magnesium hydroxide, aluminum hydroxide, or iron will interfere with absorption. Because some of the tetracyclines are not completely absorbed, any drug remaining in the intestine may inhibit sensitive intestinal microorganisms and alter the normal intestinal flora. 

In a separate experiment with zinc supplied at 9 ppm in all diets, the effect of increasing dietary calcium in calcium or magnesium precipitated tofu or egg white diets on weight gain and tibia zinc accumulation was tested. From Table IV it can be noted that the performance of tofu-fed rats relative to zinc carbonate-fed rats was quite similar at 0.4% total dietary calcium, but was reduced as dietary calcium was increased to 0.7% and to 1.2%. These results suggest that a poorly available calcium-zinc-phytate complex not present in the soy curd can form in the gastrointestinal tract when sufficient calcium is added to the diet. 

Monobasic sodium phosphate should not he administered concomitantly with aluminum, calcium, or magnesium salts since they bind phosphate and could impair its ahsorption from the gastrointestinal tract. Interaction between calcium and phosphate, leading to the formation of insoluble calcium phosphate precipitates, is possible in parenteral admix-tures.< >... 

Corley K T T, Marr C M 1998 Pathophysiology, assessment and treatment of acid-base disturbances in the horse. Equine Veterinary Education 10 255-265 Costa L R R, Eades S E, Tulley R T et al 1999 Plasma magnesium concentrations in horses with gastrointestinal tract disease. Journal of Veterinary Internal Medicine 13 274... 

Schweigel M and Martens H (2000) Magnesium transport in the gastrointestinal tract. Front Biosd 5 D666-D677. 

Sodium and potassium chlorates are low to moderately toxic in test animals. Oral administration produced irritation of the gastrointestinal tract, anemia, and methemoglobinemia. The oral LD50 values for sodium, potassium, calcium, and magnesium salts in rats are within the range 1200, 1800, 2500, and 6300 mg/kg, respectively. The toxicity data for other metal chlorates are not reported. 

---