Magnesium hydroxide dosing

Scale prevention methods include operating at low conversion and chemical pretreatment. Acid injection to convert COs to CO2 is commonly used, but cellulosic membranes require operation at pH 4 to 7 to prevent hydrolysis. Sulfuric acid is commonly used at a dosing of 0.24 mg/L while hydrochloric acid is to be avoided to minimize corrosion. Acid addition will precipitate aluminum hydroxide. Water softening upstream of the RO By using lime and sodium zeolites will precipitate calcium and magnesium hydroxides and entrap some silica. Antisealant compounds such as sodium hexametaphosphate, EDTA, and polymers are also commonly added to encapsulate potential precipitants. Oxidant addition precipitates metal oxides for particle removal (converting soluble ferrous Fe ions to insoluble ferric Fe ions). 

Aluminum Hydroxide + Magnesium Hydroxide (Maalox) [OTC] [Antacid/Aluminum Magnesium Salts] Uses Hyper-acidity (peptic ulcer, hiatal hernia, etc) Action Neutralizes gastric acid Dose Adults. 10-20 mL or 2-4 tabs PO qid or PRN Feds. 5-15 mL PO qid or PRN Caution [C, ] Disp Tabs, susp SE May cause t Mg in renal insuff, constipation, D Interactions In addition to AlOH, X effects OF digoxin, quinolones, phenytoin, Fe supl, ketoconazole EMS None OD May cause constipation, loss of appetite, painful urination, heart rhythm changes, muscle weakness, and peripheral edema symptomatic and supportive... 

Two patients with hypothyroidism taking a fixed dosage of levothyroxine took aluminium hydroxide and magnesium oxide (72). In both cases there was a marked increase in the serum concentration of TSH and low serum T4. After withdrawal of the antacids, TSH again fell. In vitro studies showed a dose-related adsorption of levothyroxine by a combination of aluminium hydroxide, magnesium hydroxide, and magnesium carbonate, but no effect of magnesium oxide alone. 

A 41-year-old woman, with liver lacerations, rib fractures, and pneumothorax after a motor vehicle accident, was given haloperidol for agitation on day 7. During the first 24 hours she received a cumulative intravenous dose of 15 mg, 70 mg on day 2, 190 mg on day 3,160 mg on days 4 and 5, and 320 mg on day 6. An hour after the first dose of 80 mg on day 7, she had ventricular extra beats followed by 5-beat and 22-beat runs of ventricular tachycardia. The rhythm strips were consistent with polymorphous ventricular tachycardia or torsade de pointes and the QTC interval was 610 ms (normally under 450 in women). She received intravenous magnesium sulfate 2 g. Concurrent medications included enoxaparin, famotidine, magnesium hydroxide, ampicillin/sulbactam, nystatin suspension, midazolam, and 0.45% saline with 20 mmol/1 of potassium chloride. She had no further dysrhythmias after haloperidol was withdrawn. Eight days after the episode of torsade de pointes she had a QTC interval of 426 ms. 

A 39-year-old woman who took high doses of aluminium and magnesium hydroxide for peptic ulcer disease (over 18 kg of elemental aluminium and 15 kg of elemental magnesium over 8 years) developed severe osteomalacia due to profound phosphate depletion (60). Bone biopsy showed stainable aluminium deposits along 28% of the total bone surface, a unique observation in a patient with normal renal function. Treatment included withdrawal of the antacid and supplementation with phosphate, calcium, and vitamin D. Her bone mineral density increased over the next 2 years. 

Rgure 10.10 Plasma levels of bishydroxycoumarin (BHC), also known as dicoumarol, in 6 subjects after a 300 mg oral dose with water (solid line), magnesium hydroxide (dotted line) or aluminium hydroxide (dashed line). Closed data points represent a significant difference from control. 

Dicoumarol + magnesium hydroxide, magnesium oxide Opposite effects have been reported (i) Decreased absorption and lower blood levels (up to 75%) of dicoumarol (ii) Increased absorption Possibly adsorption on drug leading to decreased absorption. Chelation might lead to more lipophilic species and increased absorption Space doses by 2-3 h... 

Magnesium hydroxide Note Up to four times/day PO (tablet) 622-1244 mg/dose (liquid concentrate 2.5-1.5 ml/dose (liquid) 5-15 ml/dose... 

Magnesium citrate Magnesium hydroxide Magnesium sulfate (high dose) Sodium phosphates Bisacodyl... 

In 10 healthy subjects an antacid containing aluminium/magnesium hydroxide and magnesium carbonate reduced the AUC of a single 50-mg dose of captopril by about 40%, when compared with the fasting state. However, this did not alter the extent of the reduction in blood pressure. ... 

The steady-state AUC of olmesartan 20 mg daily was 12% lower when it was given 15 minutes after a daily dose of an aluminium/magnesium hydroxide antaeid, when eompared with olmesartan alone, but this was not eonsidered to be elinieally signifieant. ... 

A well established and clinically important interaction for those receiving long-term treatment with large doses of salicylates because the serum salicylate level may become subtherapeutic. This interaction can occur with both systemic antacids (e.g. sodium bicarbonate) as well as some non-systemic antacids (e.g. aluminium/magnesium hydroxide), but only appears to occur if there is an increase in the urinary pH. Care should be taken to monitor serum salicylate levels if any antacid is started or stopped in patients where the control of salicylate levels is critical. 

About 10 mL of a 5.8% suspension of aluminium hydroxide had no effect on the bioavailability of a single 50-mg dose of diclofenac i n 7 healthy subjeets. In another study, 10 mL of magnesium hydroxide suspension (850 mg) was found to have no signifieant effect on the rate or extent of absorption of a single 50-mg dose of dielofenac in 6 healthy, fasted sub-jeets. However, there was a tendeney to an increased rate of absorption. Aluco Gel (aluminium/magnesium hydroxide) had no effect on the extent of absorption of enterie-eoated dielofenac, but may have reduced the rate of absorption. No partieular preeautions would seem to be needed if these antaeids are given with dielofenae. 

In 24 healthy subjects an aluminium/magnesium hydroxide antacid (Maalox) had no effect on the rate or extent of absorption of a single 25-mg dose of dexketoprofen, although the maximum level was slightly (13%) lower. ... 

---