Calcium carbonate dosing

PVC compounds in the window profile industry can usually accept ordinary calcium carbonate dose levels of only about 8%. But the favourable particle size distribution obtainable at the new Omya facility at Melton, on Humberside, UK, means that loadings of up to 15% are feasible, and 10% or 12% levels do not affect strength or gloss too much. Flowability and colour retention properties are also said to be excellent, and the availabiUty of these new grades is claimed to enable PVC compounders to lower their costs. 

Calcium carbonate is the salt of choice because it contains the highest concentration of elemental calcium (40%) and is the least expensive (Table 3-3). It should be ingested with meals to enhance absorption from increased acid secretion. Calcium citrate absorption is acid independent and need not be taken with meals. Because the fraction of calcium absorbed decreases with increasing dose, maximum single doses of600 mg or less of elemental calcium are recommended. 

Milk-alkali syndrome Milk-alkali syndrome, an acute illness with symptoms of headache, nausea, irritability, and weakness, or a chronic illness with alkalosis, hypercalcemia and, possibly, renal impairment, has occurred following the concurrent use of high-dose calcium carbonate and sodium bicarbonate. Hypophosphatemia Prolonged use of aluminum-containing antacids may result in hypophosphatemia in normophosphatemic patients if phosphate intake is not adequate. 

Calcium Acetate (PhosLo) [Calcium Supplement/ Anti arrhythmic/Mmeral/ Electrolyte] Uses ESRD-associated hyper-phos-phatemia Action Ca " supl w/o aluminum to X P04 absorption Dose 2-4 tabs PO w/ meals Caution [C, ] Contra t Ca Disp Gelcap SE Can t Ca, hypophosphatemia, constipation Interactions t Effects OF quinidine X effects W/ large intake of dietary fiber, spinach, rhubarb X effects OF atenolol, CCB, etidronate, tetracyclines, fluoroquinolones, phenytoin, Fe salts, thyroid hormones EMS Pts have reduced renal Fxn, monitor ECG for signs of electrolyte disturbances OD S/Sxs of hypercalcemia (confusion, weakness, GI upset, constipation, N, V, and cardiac arrhythmias) give IV fluid for diuresis symptomatic and supportive Calcium Carbonate (TumS/ Alka Mints) [Antacid/ Calcium Supplement/Mineral/ Electrolyte] [OTC] Uses Hyperacidity associated w/ peptic ulcer Dz, hiatal hernia, etc Action Neutralizes gastric acid Dose 500 mg—2 g PO PRN -1- in renal impair Caution [C, ] Disp Chew tabs, susp SE t -1- PO constipation Interactions X Effect OF tetracyclines, fluo-... 

Figure 2 Typical viscosity vs. dispersant dose for Na polyacrylate on coating grade calcium carbonate 0.5 pm - 16% solids)...

A series of slurries of high solids, dispersed ground calcium carbonate were prepared. Firstly, a sample of Carrara marble was ground without dispersant to a mean size of 0.5 fim. This was then filtered to a solids level of 76% (volume fraction 46%), before being thoroughly mixed with the required dose of sodium polyacrylate dispersant and adjusted to a constant solids level of 70%. Doses ranged from zero to 25mgg (2.5%) of calcium carbonate. Samples were then left for two days to reach a steady-state adsorption level. After this they were sheared and their viscosity (Brookfield RV, 100 rpm, spindle 3) was measured. 

Figure 4 Log (viscosity) vs. Dose for Na polyacrylate on 0.5 pm calcium carbonate at 70% solids...

Figure 7 Zeta potential of calcium carbonate as a function of Na polyacrylate dose...

Hypocalcemia PO (calcium carbonate) 1-2 g/day in 3-4 divided doses. PO (calcium glubionate) 6-18 g/day in 4-6 divided closes. IV (calcium chloride) 0.5-lg repeated q4-6h as needed. IV (calcium gluconate) 2-15g/24hr. 

When the treated water pH exceeds 9.4 to 9.6, the use of carbon dioxide to recarbonate the water is recommended. Alternatives include the use of sulfuric acid dosing, or a suitable chemical additive such as a threshold treatment or a calcium carbonate dispersant. 

The principal reason, however, why sulfuric acid is used as part of many cooling water pretreatment programs (as when dosed to the makeup line) or treatment programs (as when dosed to the tower basin) is to produce salts that are more soluble than calcium carbonate. Thus the point at which calcium salt saturation is reached is extended and the risk of fouling and crystalline scale on heat transfer surfaces is minimized. 

A 49-year-old woman, taking levothyroxine 150 micro-grams/day and calcium carbonate (three tablets daily) for prevention of osteoporosis, developed symptoms of hypothyroidism and had a raised serum TSH concentration (22 mU/1). She was advised to continue taking the same dose of levothyroxine but to separate her medications. Repeat biochemical testing 8 months later showed a normal serum TSH (3.3 mU/1). 

Calcium carbonate(eg, Turns, Os-Cal) is less soluble and reacts more slowly than sodium bicarbonate with HC1 to form carbon dioxide and CaCl2. Like sodium bicarbonate, calcium carbonate may cause belching or metabolic alkalosis. Calcium carbonate is used for a number of other indications apart from its antacid properties (see Chapter 42 Agents That Affect Bone Mineral Homeostasis). Excessive doses of either sodium bicarbonate or calcium carbonate with calcium-containing dairy products can lead to hypercalcemia, renal insufficiency, and metabolic alkalosis (milk-alkali syndrome). 

Pepto- Bismol bismuth subsalicylate calcium carbonate pink solid or solution may cause stomach upset if taken in excess of recommended dose relieves digestive difficulties by coating the digestive tract and reducing acidity... 

The use of buffering agents in solid dose forms is not as widespread as the use in parenteral products. Nevertheless, the current Handbook of Pharmaceutical Excipients lists calcium carbonate, monobasic and dibasic sodium phosphate, sodium and potassium citrates, and tribasic calcium phosphate as potential buffering agents. ... 

The development of bisphosphonates for clinical purposes began with the discovery that inorganic pyrophosphate is present in blood and urine and inhibits the precipitation of calcium and phosphate (1). Derivatives of pyrophosphate had been widely used for industrial purposes, because they inhibit the precipitation of calcium carbonate. Their principal use was as antiscaling additives in washing powders, water, and oil brines, to prevent deposition of calcium carbonate scale. It was then found that pyrophosphate binds strongly to calcium phosphate, prevents both the formation and dissolution of calcium phosphate crystals, and inhibits calcification in vitro. The bisphosphonates are used to treat bone diseases characterized by increased osteoclastic bone resorption (2). Long-term administration of low doses of oral bisphosphonates is considered to be valuable in patients with postmenopausal osteoporosis (3,4). 

In one study of the use of calcium carbonate as a phosphate binder in patients on chronic hemodialysis, there was a low incidence of hypercalcemia at daily doses below 6 g (2), whereas in another report on 26 dialysis patients who used calcium carbonate for 3 years, 42% developed new calcification (3). 

Levant JA, Walsh JH, Isenberg JI. Stimulation of gastric secretion and gastrin release by single oral doses of calcium carbonate in man. N Engl J Med 1973 289(ll) 555-8. 

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