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PubMed1992

Effects of aluminum hydroxide and calcium carbonate antacids on the bioavailability of ciprofloxacin.

This study was designed to determine the effects of an aluminum hydroxide antacid and a calcium carbonate antacid on the bioavailability of ciprofloxacin (Cipro). Cipro (750 mg) was administered orally to 12 healthy volunteers in a three-way randomized crossover design. The three treatments included Cipro alone, four 850-mg calcium carbonate tablets taken 5 min before Cipro, and three 600-mg aluminum hydroxide tablets taken 5 min before Cipro. The relative bioavailability of Cipro when given with calcium carbonate was approximately 60% of the control value. When Cipro was given with aluminum hydroxide, the relative bioavailability was approximately 15%. Urinary recovery of Cipro in the aluminum hydroxide treatment group was approximately one-fourth of that in the calcium carbonate group. Although calcium carbonate decreased absorption to a lesser extent than aluminum hydroxide, these data suggest that antacids containing either aluminum or calcium should not be given concomitantly with Cipro.

Adult↗
PubMed1993

Mechanistic study of inhibition of levofloxacin absorption by aluminum hydroxide.

The mechanisms of reduction in absorption of levofloxacin (LVFX) by coadministration of aluminum hydroxide were studied. The partition coefficient of LVFX (0.1 mM) between chloroform and phosphate buffer (pH 5.0) was reduced by 60 to 70% with the addition of metal ions such as Cu2+, Al3+, and Fe2+ (0.8 mM), which indicated the formation of LVFX-metal ion chelates. However, there was no significant difference in absorption from rat intestine between the synthetic LVFX-Al3+ (1:1) chelate (6.75 mM) and LVFX (6.75 mM) in an in situ recirculation experiment. On the other hand, Al(NO3)3 (1.5 mM) significantly inhibited the absorption of LVFX (1.5 mM) by 20% of the control in the in situ ligated loop experiment, in which partial precipitation of aluminum hydroxide was observed in the dosing solution. Data for adsorption of LVFX and ofloxacin (OFLX) from aqueous solution by aluminum hydroxide were shown to fit Langmuir plots, and the adsorptive capacities (rmax) and the K values were 7.0 mg/g and 1.77 x 10(4) M-1 for LVFX and 7.4 mg/g and 1.42 x 10(4) M-1 for OFLX, respectively. The rate of adsorption of several quinolones (50 microM) onto aluminum hydroxide (2.5 mg/ml) followed the order norfloxacin (NFLX) (72.0%) > enoxacin (ENX) (61.0%) > OFLX (47.2%) approximately LVFX (48.1%). The elution rate of adsorbed quinolones with water followed the rank order LVFX (17.9%) approximately OFLX (20.9%) approximately ENX (18.3%) > NFLX (11.9%). These results strongly suggest that adsorption of quinolones by aluminum hydroxide reprecipitated in the small intestine would play an important role in the reduced bioavailability of quinolones after coadministration with aluminum-containing antacids.

Aluminum Hydroxide↗
PubMed1976

Active immobilized antibiotics based on metal hydroxides.

The water-insoluble hydroxides of zirconium (IV), titanium (IV), titanium (III), iron (II), vanadium (III), and tin (II) have been used to prepare insoluble derivatives of a cyclic peptide antibiotic by a facile chelation process. Testing of the antibacterial activities of the products against two gram-positive and two gram-negative bacteria showed that in the majority of cases the water-insoluble antibiotics remained active against those bacteria susceptible to the parent antibiotic. The power of the assay system has been extended by the novel use of colored organisms to aid determinations where the growth of normal organisms could not be distinguished from the appearance of the supporting material. Insoluble derivatives of neomycin, polymyxin B, streptomycin, ampicillin, penicillin G, and chloramphenicol were prepared by chelation with zirconium hydroxide, and these derivatives similarly reflected the antibacterial activities of the parent compounds. Several of the metal hydroxides themselves possess antibacterial activity due to complex formation with the bacteria. However, the use of selected metal hydroxides can afford a simple, inexpensive, and inert matrix for antibiotic immobilization, resulting in an antibacterial product that may possess slow-release properties. The mechanisms by which the metal hydroxide-antibiotic association-dissociation may occur are discussed.

Anti-Bacterial Agents↗
PubMed1999

Catalysis by metal-activated hydroxide in zinc and manganese metalloenzymes.

The metal-activated hydroxide ion is a critical nucleophile in metalloenzymes that catalyze hydrolysis or hydration reactions. The most common metal used is zinc; occasionally, other transition metals such as manganese are required. Human carbonic anhydrase II and rat liver arginase serve as well-studied paradigms of zinc and manganese metalloenzymes, respectively. Comparative structure-function relationships between these two metalloenzymes highlight parallels in the chemistry of metal-activated hydroxide: (a) the protein environment of metal-bound hydroxide modulates its reactivity; (b) a hydrogen bond with metal-bound hydroxide holds it in the proper orientation for catalysis; (c) nonmetal substrate-binding sites are implicated in both enzyme mechanisms; and (d) regeneration of metal-bound hydroxide ion from a metal-bound water molecule requires proton transfer to bulk solvent mediated by a histidine proton shuttle residue. Interestingly, the electrostatics of catalysis differ between the two enzymes, in that the first step of catalysis requires formation of a negatively charged transition state in the carbonic anhydrase II mechanism, whereas a neutral transition state is approached in the arginase mechanism. This electrostatic feature may contribute to the differences in the chemistry, the metal binding sites, and the metal specificity between these two enzymes.

Animals↗
PubMed1986

Bone aluminum deposition in maintenance dialysis patients treated with aluminium-free dialysate: role of aluminium hydroxide consumption.

Postmortem iliac crest biopsies were performed on 16 uremic patients. 3 had been treated conservatively while 13 had been entered into a maintenance dialysis program. The dialysate was treated by reverse osmosis for more than 10 years, and the aluminium concentration was consistently below the detection limit of 0.15 mol/l. 14 patients had been treated with aluminium hydroxide. Bone histomorphometry, aluminium labelling intensity, osteoid surface aluminium labelling extent (Al/OBI) and bone aluminium concentration were measured. 14 patients had significant bone aluminium deposition, including 2 who were not on dialysis of whom 1 had not received aluminium hydroxide. Bone aluminium concentration and labelling intensity were correlated to total aluminium hydroxide consumption (p less than 0.001, p less than 0.05) and present dose (p less than 0.01, p less than 0.01), while Al/OBI was not. The two patients with the highest aluminium concentrations had symptomatic osteomalacia, but 4 patients with significantly raised concentrations and mineralisation front labelling had secondary hyperparathyroidism. It is concluded that bone aluminium deposition occurs despite the use of aluminium-free dialysate and is associated with total and present aluminium hydroxide consumption; heavy aluminium deposition is associated with severe and symptomatic osteomalacia, but can also be observed in the presence of predominant hyperparathyroidism; aluminium deposition can occur in the absence of treatment with dialysis or aluminium hydroxide; bone aluminium concentration and labelling intensity are a better measure of bone deposition than Al/OBI.

Adolescent↗
PubMed1985

Effects of calcium hydroxide-containing pulp-capping agents on pulp cell migration, proliferation, and differentiation.

The findings from the recent literature on pulpal cell responses to the application of calcium hydroxide to exposed pulps are described. The effect of calcium hydroxide on healthy and inflamed pulp is discussed. The effect of incorporation of calcium hydroxide in various pulp-capping agents is presented. The initial effect of calcium hydroxide applied to exposed pulp is the development of a superficial three-layer necrosis. The beneficial effect of calcium hydroxide is regarded as the result of the chemical injury caused by the hydroxyl ions, limited by a zone of firm necrosis against the vital tissue, and the toleration of calcium ions by the tissue. The firm necrosis causes slight irritation and stimulates the pulp to defense and repair. The observed sequence of tissue reactions is that which is expected when connective tissue is wounded. It starts with vascular and inflammatory cell migration and proliferation, to control and elimination of the irritating agent. This is followed by the repair process, including migration and proliferation of mesenchymal and endothelial pulp cells and formation of collagen. When the pulp is protected from irritation, odontoblasts differentiate, and the tissue formed assumes the appearance of dentin, i.e., the function of the pulp is normalized. The mineralization of the collagen starts with dystrophic calcification of both the zone of firm necrosis and the degenerated cells in the adjacent tissue, leading to deposition of mineral in the newly-formed collagen. The presence of calcium ions stimulates precipitation of calcium carbonate in the wound area and thereby contributes to the initiation of mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Defluoridation of water at high pH with use of brushite, calcium hydroxide, and bone char.

The aim of this study was to improve the efficiency of the bone-char method of water defluoridation by pre-treating the water with brushite and calcium hydroxide. Various amounts of brushite, calcium hydroxide, and bone char were suspended batchwise in 100 mL of distilled water containing 0.53 mmol/L fluoride for 24 h under gentle agitation. At suitable intervals, pH and the concentrations of fluoride, calcium, and phosphate in the water were determined and, when possible, the degrees of saturation with respect to brushite, hydroxyapatite, and fluorapatite calculated. Bone char used alone took up fluoride slowly and inefficiently. The addition of brushite and calcium hydroxide resulted in high concentrations of calcium and phosphate, making the solutions highly supersaturated with respect to fluorapatite, and led to a 20-fold increase in fluoride removal from the water. The combined use of all three salts left low concentrations of phosphate in solution and optimized the fluoride uptake capacity. Repeated use of the same bone char for 18 consecutive runs demonstrated that uptake of fluoride by the bone char was improved by repeated use, provided that brushite and calcium hydroxide were added. Therefore, addition of the two salts to the water may prolong the life of the bone char indefinitely, ensure the removal of fluoride, and thus avoid the problem of determining when the bone char is exhausted. In conclusion, we show that the bone-char defluoridation technique can be improved by addition of brushite and calcium hydroxide to the water. The problem of high terminal pH remains, however, and further work is required to improve potability.

Animals↗
PubMedDate not supplied

Comparison of the effects of magnesium hydroxide and a bulk laxative on lipids, carbohydrates, vitamins A and E, and minerals in geriatric hospital patients in the treatment of constipation.

In a crossover study the effects of magnesium hydroxide on serum lipids, carbohydrates, vitamins A and E, uric acid and whole blood minerals were compared with those of a bulk laxative containing plantago rind and sorbitol in 64 constipated, elderly long-stay patients, 55 of whom were receiving diuretics. Hypomagnesaemia occurred in 11 (17%) patients after bulk laxative and in two (2%) patients after magnesium hydroxide treatment. There was a slight reduction in low values of high-density lipoprotein cholesterol and high values of triglycerides after magnesium hydroxide treatment. There were no significant differences in plasma lipids, whole blood minerals or vitamins A and E using either laxative. Negative correlations were found between the increase in serum concentrations of magnesium and glycosylated haemoglobin A1 (P less than 0.02) and the serum level of uric acid (P less than 0.01). These results suggest that the long-term effects of magnesium hydroxide and bulk laxative on the absorption of nutrients may not be significantly different. Magnesium hydroxide, however, may have beneficial effects on lipid disorders, impaired glucose tolerance and hyperuricaemia in magnesium deficiency due to diuretics and thus may be a favourable laxative for use in bedridden geriatric patients receiving diuretics.

Aged↗
PubMed2005

Hydroxide and proton migration in aquaporins.

Hypothetical hydroxide and proton migration along the linear water chain in Aquaporin GlpF from Escherichia coli are studied by ab initio Car-Parrinello molecular dynamics simulations. It is found that the protein stabilizes a bipolar single file of water. The single file features a contiguous set of water-water hydrogen bonds in which polarization of the water molecules vary with position along the channel axis. Deprotonation of the water chain promotes the reorientation of water molecules while the hydroxide ion rapidly migrates by sequentially accepting protons from the neighboring water molecules. The hydroxide ion is not attracted by a conserved, channel-lining arginine residue, but is immobilized at two centrally located, conserved Asparagine-Proline-Alanine motifs where fourfold coordination stabilizes the ion. Hydroxide transition from the channel vestibules into the channel lumen is strongly influenced by electrostatic coupling to two conserved oppositely aligned macrodipoles. This suggests that the macrodipole's negative poles play a role in preventing hydroxide ions from entering into the channel's inner vestibules. Water protonation within the lumen facilitates water reorientation and subsequent proton expelling occurs. In the periplasmic half-channel, expelling occurs via the Grotthuss mechanism. Protonation within the cytoplasmic half-channel implies wire-breakage at the Asn-Pro-Ala motifs. The proton is here diffusively rejected as (H(5)O(2))(+).

Alanine↗
PubMed1978

Effect of oral administration of calcium carbonate, aluminum hydroxide gel and dihydrotachysterol on renal acidosis.

The effects of oral administration of calcium carbonate, aluminum hydroxide gel, dihydrotachysterol (DHT) and sodium bicarbonate on metabolic acidosis and plasma calcium and phosphate were studied in 7 patients with chronic renal failure. Single administration of calcium carbonate alleviated the acidosis and increased the urinary bicarbonate excretion. These effects were potentiated when aluminum hydroxide gel was administered in combination with calcium carbonate. The plasma calcium was increased by this combination therapy. The effects of these two agents on acidosis and plasma calcium were further enhanced by the additional administration of DHT. Urinary bicarbonate excretion was less during the treatment with aluminum hydroxide gel and calcium carbonate than with aluminum hydroxide gel and sodium bicarbonate, when the excretions were compared at the similar concentrations of plasma bicarbonate. Aluminum hydroxide gel and DHT are likely to enhance the effect of calcium carbonate, which works as an alkalinizing salt on acidosis, probably through increasing calcium absorption in the intestine. And the three agents suppress the leak of bicarbonate into the urine contributing to the improvement of acidosis.

Acidosis↗
PubMed1975

Reaction of the human dental pulp to silver amalgam restorations. The modifying effect of treatment with calcium hydroxide.

Cavities were prepared in 43 bicuspid teeth using two general categories of cavity depth. In the "deep" cavities the bottom was placed in the inner third of the dentin. In the "intermediate depth" cavities the bottom was positioned in the middle third of the dentin. The bottom of the cavities was either rubbed with calcium hydroxide, covered with calcium hydroxide, or left unlined before filling according to the wet amalgam technique. The teeth were extracted after 1 week and examined histologically. All cases, except 2 with deep and 1 with intermediate depth rubbed cavities, showed local vascular dilatation in the pulp underneath the cavity. In addition, all teeth with deep unlined cavities showed inflammatory cells as did 1 with an intermediate depth unlined cavity. There were fewer displaced odontoblast nuclei in the dentin in the calcium hydroxide-treated groups. The milder reactions in the rubbed or covered groups are probably due to the restrictive effect by calcium hydroxide on penetration of amalgam components. In the teeth with deep cavities there were only minor differences between the ones which had been rubbed and those which had been covered with calcium hydroxide.

Calcium Hydroxide↗
PubMed1999

Effect of vehicle on antimicrobial properties of calcium hydroxide pastes.

The current discussion about the importance of intracanal dressings and the effect of vehicles on calcium hydroxide pastes is justified by controversy concerning the achievement of complete disinfection after preparation of infected root canals and the real antimicrobial effect of these vehicles. The aim of this study is to investigate the role of vehicles in the antimicrobial effect of calcium hydroxide pastes. Well-conducted research about the characteristics of calcium hydroxide, such as antimicrobial potential, physico-chemical aspects and histocompatibility, gives credibility to the choice of this medication in several clinical situations. Different vehicles have been added to calcium hydroxide in an attempt to enhance its properties. Scientific reasoning indicates the use of hydrosoluble vehicles (distilled water, saline) associated with calcium hydroxide because of their chemical characteristics of dissociation, diffusibility and filling capability which are decisive for the biological behavior, i.e., antimicrobial qualities and induction of tissue repair.

Anti-Infective Agents, Local↗
PubMed2003

[Calcium hydroxide-based pastes used in endodontics].

The aim of the present study is to propose a classification of calcium hydroxide pastes on the basis of the vehicle that retains the calcium hydroxide. The vehicle determines the working characteristics of the calcium hydroxide: viscous and only vehicles prolong the action of the calcium hydroxide as compared with water-soluble substances. Physicochemical properties of the vehicle may limit the effectiveness in disinfecting the entire root canal system. As calcium hydroxide is not effective against all bacterial species found in root canal infections, associations with other medicaments have been proposed to enhance the efficacy of the intracanal medication.

Anti-Infective Agents, Local↗
PubMed1987

Constipation in elderly long-stay patients: its treatment by magnesium hydroxide and bulk-laxative.

Sixty-four geriatric long-stay patients aged 65 years or older participated in the trial. All were using laxatives prior to the study. For the study laxatives the mean dose of magnesium hydroxide was 25 ml daily and for bulk-laxative 8.7 g daily. Magnesium hydroxide caused a more frequent bowel habit (13.2 vs. 10.4/4 weeks, p less than 0.001) than bulk-laxative and additional laxative bisacodyl was not needed as often as with bulk-laxative (2.3 vs. 3.3/4 weeks, p less than 0.01). Also the stool consistency was more normal during the magnesium hydroxide treatment. In two patients serum magnesium was over 1.25 mmol/l after the magnesium hydroxide treatment but there were no clinical signs of hypermagnaesemia. Our study indicated magnesium hydroxide to be more efficient than bulk-laxative in treating constipation in elderly long-stay patients.

Aged↗
PubMed1985

Modulation of the human immune response by the non-toxic and non-pyrogenic adjuvant aluminium hydroxide: effect on antigen uptake and antigen presentation.

The regulatory effects of an adjuvant (aluminium hydroxide) on the early phase of the immune response have been investigated. Adsorbing a soluble antigen (tetanus toxoid) to aluminium hydroxide led to a significant increase (P less than 0.001) in antigen-induced T-cell proliferation (macrophage-T-cell interaction, MTI) making aluminium hydroxide-adsorbed antigens especially suitable to study immunoregulatory changes in the early phase of the immune response. First studies revealed that this increase was due to an enhancement of antigen uptake by the antigen-presenting cell. However, under conditions allowing for the uptake of comparable amounts of soluble (TTs) or aluminium hydroxide-absorbed (TTAL) antigen, T-cell proliferation in response to TTAL was still higher than in response to TTS. This difference was especially pronounced if suboptimal antigen concentrations were used and could be explained by differences in the TTS-versus TTAL-induced release of interleukin-1 (IL-1). Pulsing with TTAL led to a substantial increase in IL-1 release by monocytes (MO) which then subsequently augmented antigen-induced T-cell proliferation. This was further supported by addition of exogenous IL-1 to cultures of T cells and TTS-pulsed MOs, which also significantly increased the T cells' proliferative response. These findings demonstrate that in the early phase of the immune response, aluminium hydroxide exerts its regulatory effect at the level of the antigen-presenting and mediator-releasing accessory cell.

Adjuvants, Immunologic↗
PubMedDate not supplied

Effects of aluminum hydroxide on fluoride and calcium metabolism.

In order to determine whether and to what extent aluminum affects the absorption of fluoride in man, a study of the effect of aluminum hydroxide on fluoride metabolism was carried out under strictly controlled dietary conditions. Relatively small amounts of aluminum hydroxide were used: 30 ml given three times daily, containing a total of 1.8 gm aluminum. Fluoride and calcium balances were determined in control studies and during the intake of aluminum hydroxide. The fluoride intake of approximately 4 mg/day was due to the fluoride content of the diet and the drinking water. A study was also carried out in patients with osteoporosis who received a high fluoride intake of approximately 50 mg/day of sodium fluoride therapeutically for osteoporosis. The intake of aluminum hydroxide was associated with a significant increase of the fecal fluoride and with a significant decrease of the net absorption of fluoride, by an average of 57%, irrespective of the intake of fluoride. The-plasma fluoride levels decreased by 41%. The fluoride balances were either negative or less positive. Relatively small amounts of aluminum hydroxide resulted in phosphorus depletion, in an increase of the urinary calcium, and in negative calcium balances.

Adult↗
PubMed1999

Volume Changes Due to SO2-4, SeO2-4, and H2PO-4 Adsorption on Amorphous Iron(III) Hydroxide in an Aqueous Suspension.

Volume changes due to SO2-4, SeO2-4, and H2PO-4 adsorption on amorphous iron(III) hydroxide were determined by dilatometry in a mixture comprising an aqueous solution of Na2SO4, Na2SeO4, or NaH2PO4 and amorphous iron(III) hydroxide suspended in 0.1 mol dm-3 NaClO4 at an initial pH ranged from 4.50 to 6.50. System volumes increased during SO2-4, SeO2-4, and H2PO-4 adsorption on amorphous iron(III) hydroxide, suggesting that some hydrated water around aqueous SO2-4, SeO2-4, or H2PO-4 ions and amorphous iron(III) hydroxide were released to the bulk. The volume changes due to SO2-4, SeO2-4, and H2PO-4 adsorption at initial pH 4.50 were +18, +18, and +14 cm3 mol-1, respectively. Phosphate, which adsorbed as an inner-sphere complex, released most of its hydration water to the bulk. The volume changes due to SO2-4 and SeO2-4 adsorption indicated that they were dehydrated at the water/amorphous iron(III) hydroxide interface. The smaller changes in volume for H2PO-4 compared to SO2-4 and SeO2-4 may be explained by differences of charges and adsorption mechanisms of these oxoanions. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Kinetics of Hydrolysis of Phenyl Acetates Catalyzed by the Zinc(II) Complex of 1,5,9-Triazacyclododecane. Evidence for Attack of Water or Hydroxide Ion at the Coordinated Ester.

Rates for hydrolysis of substituted phenyl acetates were measured in the presence of the Zn(II) complex of 1,5,9-triazacyclododecane. The kinetic data are incompatible with the mechanism in which the water and hydroxide ion coordinated to the metal center makes a nucleophilic attack at the ester linkage. Instead, the results support the mechanism in which the ester is first complexed to the metal center and then water or hydroxide ion makes a nucleophilic attack at the complexed ester. The kinetic data further indicate that the electrostatic interaction between the cationic metal center and the anionic hydroxide ion facilitates the attack of hydroxide ion at the complexed ester. In addition, the C-O bond of the ester is not cleaved significantly in the rate-determining transition state for attack by both water and hydroxide ion.

Journal Article↗