Nanoadduct relieves: Alleviation of developmental toxicity of Cr(VI) due to its spontaneous adsorption to Mg(OH)2 nanoflakes

During pregnancy, both the mother and fetus are vulnerable to environmental pollution by particulate matters and chemicals. Although the toxicity of free pollutants has been frequently reported, the impact of nanoparticle/pollutant adducts on the vulnerable pregnant population remains unclear. In this study, pregnant mice were orally exposed to Mg(OH)2 nanoflakes and nanoflakes adsorbed with Cr(VI) anions during the peri-implantation and organogenesis stages of pregnancy at doses that did not induce systemic toxicity or pregnancy complications. The nano-Mg(OH)2/Cr(VI) adducts formation reduced fetal developmental toxicity compared with the toxicity induced by the same concentration of free Cr(VI) anions.

A study of the potential application of nano-Mg(OH)2 in adsorbing low concentrations of uranyl tricarbonate from water

This work aims at the investigation of nano-Mg(OH)(2) as a promising adsorbent for uranium recovery from water. Systematic analysis including the uranium adsorption isotherm, the kinetics and the thermodynamics of adsorption of low concentrations of uranyl tricarbonate (0.1-20 mg L(-1)) by nano-Mg(OH)(2) was carried out. The results showed a spontaneous and exothermic uranium adsorption process by Mg(OH)(2), which could be well described with pseudo second order kinetics. Surface site calculation and zeta potential measurement further demonstrated that UO(2)(CO(3))(3)(4-) was a monolayer adsorbed onto nano-Mg(OH)(2) by electrostatic forces. Accordingly, the adsorption behavior met the conditions of the Langmuir isotherm. Moreover, in most of the reported literature, nano-Mg(OH)(2) had a higher UO(2)(CO(3))(3)(4-) adsorption affinity b, which implied a higher adsorption amount at equilibrium in a dilute adsorbate system. The significance of the adsorption affinity b for choosing and designing adsorbents with respect to low concentration of resources/pollutants treatment has also been assessed.

The effects of oral magnesium hydroxide administration on rumen fluid in cattle

This study was conducted to determine the effects of oral magnesium hydroxide administration on rumen fluid in cattle. Six lactating Holstein cows (4-7 years of age) with rumen fistulas were studied. Cattle were randomly assigned to receive boluses of magnesium hydroxide (162 g) or a powdered form (450 g dissolved in 3.5 L of water) PO daily for 3 days. Analysis of rumen fluid, blood gas tensions, and pH and measurement of serum magnesium concentrations were conducted daily. The study was discontinued after 72 hours, or sooner if rumen pH exceeded 8.0. After at least 3 weeks, the study was repeated with each cow receiving the other form of magnesium hydroxide (powder or bolus). Compared with baseline rumen pH (mean +/- SD: 6.22 +/- 0.28), magnesium hydroxide boluses caused a significant increase (P < .05) in rumen pH after 48 (7.27 +/- 0.11) and 72 (8.01 +/- 0.16) hours of administration, whereas the powdered form caused a significant increase (P < .05) in rumen pH after 24 (7.54 +/- 0.19) and 48 (8.43 +/- 0.22) hours of administration. Both the powdered and bolus forms of magnesium hydroxide decreased rumen protozoal numbers and increased methylene blue reduction times compared with baseline values. There was no change in blood pH, bicarbonate, or base excess values. Serum magnesium concentrations were significantly increased (P < .05) in cows that received the magnesium hydroxide powder. The results of this study indicate that magnesium hydroxide has a potent alkalinizing effect on rumen pH and significantly decreases rumen microbial activity.

Lack of pharmacokinetic interaction between the oral anti-influenza neuraminidase inhibitor prodrug oseltamivir and antacids

AIMS

Oseltamivir is an oral ester prodrug of its active metabolite Ro 64-0802, a potent and selective neuraminidase inhibitor of the influenza virus. The object of this study was to evaluate whether the oral absorption of oseltamivir was reduced in the presence of two main classes of antacid, Maalox(R) suspension (containing magnesium hydroxide and aluminium hydroxide) and Titralac(R) tablets (containing calcium carbonate).

METHODS

Twelve healthy volunteers completed a randomized, single dose, three-period crossover study. Each volunteer received in a fasted state, 150 mg oseltamivir alone (Treatment A), 150 mg oseltamivir with a 20 ml Maalox suspension (Treatment B), and 150 mg oseltamivir with four Titralac tablets (Treatment C), with 7-10 days washout in between treatments. Plasma and urine concentrations of oseltamivir and Ro 64-0802 were measured using a validated h.p.l.c./MS/MS assay. Pharmacokinetic parameters were calculated for oseltamivir and Ro 64-0802. Since antacids are locally acting drugs and generally not expected to be absorbed substantially into the systemic system, no plasma or urine concentrations of antacids were measured.

RESULTS

Bioequivalence was achieved for the primary pharmacokinetic parameters Cmax and AUC(0, infinity ) of Ro 64-0802 following administration of oseltamivir with either Maalox suspension or Titralac(R) tablets vs administration of oseltamivir alone. The bioavailability (90% confidence intervals) of Ro 64-0802 following administration of oseltamivir together with Maalox suspension vs administration of oseltamivir alone, was 90% (83.6, 96.9%) for C(max) and 94.1% (91.4, 96.9%) for AUC(0, infinity); similarly, for Titralac tablets, the equivalent values were 95.1% (88.3, 102%) for C(max) and 94.7% (91.9, 97.5%) for AUC(0, infinity).

CONCLUSIONS

The coadministration of either Maalox suspension or Titralac tablets with oseltamivir has no effect on the pharmacokinetics of either oseltamivir or Ro 64-0802, and conversely, there is no evidence that coadministration with oseltamivir has an effect on the safety and tolerability of either Maalox suspension or Titralac tablets. There was no pharmacokinetic interaction between oseltamivir with either antacid, demonstrating that the oral absorption of oseltamivir was not impaired in the presence of antacids containing magnesium, aluminium or calcium.

The pharmacokinetic and metabolic profile of olmesartan medoxomil limits the risk of clinically relevant drug interaction

Orally administered olmesartan medoxomil was rapidly absorbed from the gastrointestinal tract and converted during absorption to olmesartan, the pharmacologically active metabolite that was subsequently excreted without further metabolism. The medoxomil moiety was released as diacetyl that was rapidly cleared by further metabolism and excretion. Peak plasma concentrations of olmesartan occurred 1-3 h after administration, after which concentrations decreased quickly. The elimination half-life was 10-15 h. Olmesartan medoxomil was not measurable in plasma and excreta. The volume of distribution was low, consistent with limited extravascular tissue distribution. Bioavailability (Cmax and area under the curve) increased approximately in proportion with dose, after single and multiple daily oral doses, over the therapeutic dose range (up to 40-80 mg daily), above which systemic availability of olmesartan increased less than proportionally with increase in dose. Steady-state plasma concentrations of olmesartan were reached within the first few daily oral doses. On average, approximately 40% of systemically available olmesartan was excreted by the kidneys, the remainder being excreted in faeces, following secretion in bile. Renal clearance (0.5-0.7 l/h) was independent of dose, accounting for approximately 9-12% of an oral dose. The absolute bioavailability of olmesartan from olmesartan medoxomil tablets was 28.6%. Olmesartan exhibited little or no binding to blood cells. No clinically significant steady-state pharmacokinetic interactions were observed following co-administration of olmesartan medoxomil with digoxin, warfarin and aluminium magnesium hydroxide (antacid), supporting the low potential for clinically significant pharmacokinetic interactions to occur between olmesartan medoxomil and co-administered drugs.

Pharmacokinetic drug interaction study: administration of ceftibuten concurrently with the antacid mylanta double- strength liquid or with ranitidine

This study investigated the influence of antacid (Mylanta Double-Strength Liquid; J & J-Merck Consumer, Fort Washington, PA) and the H2 antagonist ranitidine on the pharmacokinetics of ceftibuten, a once-daily oral cephalosporin. Eighteen male volunteers received, in a randomized, three-way, crossover design, a single oral 400-mg dose of ceftibuten after an overnight fast (1) alone, (2) with antacid (60 mL), and (3) with ranitidine (after 3 days of dosing, 150 mg/12 hours). Serial blood and urine samples were collected during a 24-hour period after each administration, with a 1-week washout between treatments. Ceftibuten, and its metabolite ceftibuten-trans, were analyzed in plasma and urine by high-performance liquid chromatography. Bioavailability parameters, maximum plasma concentration and area under the plasma concentration-time curve to infinity of ceftibuten were unaffected by treatment with antacid. These parameters were somewhat higher when ceftibuten was administered with ranitidine, but they were still within the ranges seen in normal healthy volunteers. The excretion of ceftibuten was independent of treatment. The concentrations of ceftibuten-trans were low in both plasma and urine with all three treatments. It is concluded that the co-administration of antacid and ranitidine are unlikely to affect the bioavailability and antibacterial efficacy of ceftibuten.

Influence of the antacid Maalox and the H2-antagonist cimetidine on the pharmacokinetics of cerivastatin

The possible influence of Maalox 70, an antacid based on magnesium-aluminum hydroxide, and the H2-antagonist cimetidine, both commonly prescribed in hypercholesterolemic patients, on the pharmacokinetics of the new HMG-CoA reductase inhibitor cerivastatin was investigated in 2 separate studies in 8 healthy young male subjects each. Cerivastatin plasma concentration/time profiles were assessed by a specific HPLC assay; in addition, total immunoreactive drug (cerivastatin plus metabolites) was determined by RIA. Single oral doses of 200 micrograms cerivastatin were administered under fasting conditions without or with 10 ml Maalox 70 suspension. The mean AUC and Cmax ratios (combined dosing/monodosing) including 90% confidence intervals were 0.92 (0.73-1.15) and 0.89 (0.72-1.10) for the HPLC data, and 0.99 (0.85-1.14) and 1.03 (0.82-1.30) for the RIA data, respectively. Thus, no interaction of the simultaneous administration of Maalox 70 on the pharmacokinetics of cerivastatin was observed. In a similar controlled, randomized nonblind 2-way crossover design the influence of the H2- antagonist and well-known cytochrome P450 enzyme inhibitor cimetidine was investigated. Eight healthy young male volunteers received single oral doses of 200 micrograms cerivastatin alone or on the fourth day of a 4-day cimetidine 400 mg b.i.d. pretreatment. The mean AUC and Cmax ratios (combined dosing/monodosing) including 90% confidence intervals were 0.98 (0.90-1.08) and 0.91 (0.78-1.07) for the RIA data, and 0.89 (0.82-0.96) and 0.93 (0.80-1.09) for the HPLC data, respectively, clearly indicating that cimetidine and cerivastatin did not interact pharmacokinetically. These results do not only reflect the apparent insensitivity of cerivastatin absorption to possible changes in gastric pH, but demonstrate that the metabolic pathways of cerivastatin, involved in its first-pass metabolism and elimination, are rather insensitive to cytochrome P450 enzyme inhibition induced by cimetidine.

Interaction between sotalol and an antacid preparation

AIMS

The aim of the study was to investigate the pharmacokinetic interaction between sotalol and antacids, and its pharmacodynamic relevance.

METHODS

In a randomized cross-over design with three treatment groups, six healthy volunteers received orally either 160 mg of sotalol alone (phase 1), or 160 mg sotalol plus 20 ml of a suspension of an antacid (MAH; magnesium hydroxide (1200 mg) and aluminium oxide (1800 mg)) (phase 2) or 160 mg sotalol plus the antacid given 2 h after sotalol administration (phase 3). Heart rate and plasma sotalol concentrations were measured before and 1, 2, 3, 4, 6, 8, 12 and 24 h after sotalol administration. Urinary sotalol excretion was measured for 24 h after sotalol application.

RESULTS

Cmax of sotalol decreased from 1.22 +/- 0.22 mgl-1 (phase 1) to 0.89 +/- 0.29 mgl-1 (phase 2) and increased again to 1.27 +/- 0.18 mgl-1 in phase 3. A similar significant change was noted in AUC (15.6 +/- 2.75 mgl-1, 12.3 +/- 3.04 mg h l-1 and 15.0 +/- 2.06 mgl-1) and in the amount of cumulative urinary excretion (79.2 +/- 11.1 mg, 72.1 +/- 11.2 mg and 80.6 +/- 7.9 mg), respectively. tmax and elimination half-life (t1/2,z) of sotalol remained unchanged in the presence of MAH. After combined administration with MAH, the area under the heart rate curve of sotalol was reduced between 0 and 4 h when compared across treatments.

CONCLUSIONS

Combined administration of sotalol and MAH decreased the serum sotalol levels. The interaction can be avoided by a two hour interval between application of these drugs.

Lack of interaction between valaciclovir, the L-valyl ester of acyclovir, and Maalox antacid

Valaciclovir is rapidly and extensively converted to acyclovir. In this study we investigated the potential interaction between oral valaciclovir and Maalox. On each of three occasions 18 healthy volunteers received a single oral dose of 1000 mg valaciclovir, or 30 mL Maalox 65 min after valaciclovir administration, or 30 mL Maalox 30 min before valaciclovir. Acyclovir plasma concentrations and pharmacokinetic parameters were not significantly affected by administration of Maalox before or after valaciclovir. Therefore, there is no need for restriction of valaciclovir dosing in patients receiving antacid medication.

Interaction of meloxicam with cimetidine, Maalox, or aspirin

Meloxicam is a new enol carboxamide nonsteroidal antiinflammatory drug (NSAID). Preclinical studies have indicated that it possesses a high antiinflammatory potency and a low ulcerogenic potency. This open, randomized, crossover study was conducted to examine the effects of aspirin, the antacid Maalox (Rhone-Poulenc Rorer, Cologne, Germany), and cimetidine on the pharmacokinetics and bioavailability of a single oral dose of meloxicam 30 mg in healthy male volunteers. Plasma concentrations of meloxicam were determined and subjected to noncompartmental pharmacokinetic analysis. Meloxicam was well tolerated, and concomitant treatment with cimetidine or Maalox had little or no effect on the plasma concentration-time curves, maximum plasma concentration (Cmax), or the area under the plasma concentration-time curve (AUC0-infinity) of meloxicam. Concurrent treatment with aspirin increased plasma concentrations of meloxicam, increasing Cmax by approximately 25% and AUC0-infinity by 10%. These differences were not considered to be clinically relevant, and no adjustments of meloxicam dose should be required with coadministration of aspirin, Maalox, or cimetidine.

Gastric emptying of two radiolabelled antacids with simultaneous monitoring of gastric pH

The aim of this study was to assess the gastric emptying rate of two antacids using an scintigraphic technique and simultaneous monitoring of gastric pH in 16 healthy male volunteers. Ten ml of Talcid (hydrotalcite 1 g) and Maalox (Mg-Al-hydroxide), with a similar neutralization capacity, were labelled with technetium-99m using a pyrophosphate bridge. Labelled antacids were given on separate days (within 2 weeks), 1 h after a standard meal. Intragastric pH was measured for at least 4 h, using ambulatory pH-metry with a dual-crystant antimony catheter. Continuous monitoring was started 1 h prior to the meal (baseline) and lasted 3 h (post-prandial, post-antacid and final periods). The antacid capacity of labelled and unlabelled antacids was similar. The mean percentages of antacids retained in the stomach fitted a linear model. The mean half-emptying time of Talcid was 63.9 +/- 27.9 min, while that of Maalox was 57.3 +/- 23.9 min (P = NS). The recordings of gastric pH (mean values of pH for each period) showed a similar profile for both antacids. The mean pH (Maalox vs Talcid) was 1.69 vs 2.07 in the baseline period, 1.95 vs 1.93 in the post-prandial period, 1.79 vs 1.15 in the post-antacid period (P = NS) and 0.4 vs 0.52 in the final period (P < 0.05 vs prior periods). In conclusion, the gastric emptying of Talcid and Maalox was similar and pH profiles were parallel and remained unchanged for the two antacids within the first hour of intake. A significant decrease in pH was observed 1 h after intake of the antacids, suggesting a possible rebound effect.

The kinetics of aluminium-containing antacid absorption in man

The kinetics of aluminium absorption were determined in patients with duodenal ulcer and in 2 normal males after taking the antacid Tisacid (Biogal, Hungary). A peak serum aluminium of 54.5 micrograms/l was reached at 30 min, returning to the initial value of 6.8 micrograms/l at 3 h after the oral intake. Urinary but not serum aluminium increased in parallel to the amount of drug taken. The serum Al values are considerably influenced by the time of sampling. Owing to the rapid absorption and excretion of aluminium, there appears to be no danger of aluminium deposits in the tissues or of neurological alterations, provided renal function is normal.

Orange juice enhances aluminium absorption from antacid preparation

Aluminium absorption from four doses of the antacid preparation 'Aludrox' when taken alone, with orange juice or with milk was compared by measuring the change in urinary aluminium following Aludrox dosage in 15 normal adults. There was an approximately 10-fold increase in 24 h urinary aluminium excretion following the Aludrox plus orange juice (232 micrograms) which was significantly higher than that following Aludrox alone (62 micrograms) (P < 0.001), but milk had no effect on aluminium absorption. The results showed that orange juice greatly enhanced aluminium absorption and should not therefore be taken in conjunction with aluminium-containing antacid preparations.

Hyperaluminaemia in critically ill patients: role of antacid therapy and impaired renal function

A significant rise in serum concentrations of aluminum was demonstrated in 23 patients prophylactically treated with the antacid magaldrate, whereas no increase in serum aluminium was observed in another 26 critically ill patients, in whom the use of antacids was avoided. In parallel, urinary excretion rates of aluminum rose to values close to maximum 72 h after antacid therapy had been started. Hyperaluminaemia was most marked in patients with acute renal failure undergoing continuous haemofiltration, but a significant increment in serum aluminium was also noted in patients with impaired renal function in the predialytic state. In the latter group and in patients with normal renal function there was a significant negative correlation between urinary excretion rates of aluminium and creatinine clearance after 48 h of treatment suggesting an enhancement of gastrointestinal absorption of aluminium in the presence of chronic renal failure. Maximum serum concentrations of aluminium did attain critical values in some patients with acute renal failure, but no overt signs of aluminium toxicity were noted. However, in light of both, possible subtle toxicity and enhanced absorption of aluminium in critically ill patients with renal failure, the prophylactic use of antacids in this setting should be re-evaluated cautiously.

Gastric emptying of two radiolabelled antacids

The rate of gastric emptying of two antacids, magaldrate and Maalox, was investigated using scintigraphy. Successful labelling of the antacids was carried out with 99mTc. The stability of the 99mTc-labelled antacids was satisfactory and there was no difference in antacid capacity between the labelled and unlabelled antacids. The studies were carried out on 15 healthy male volunteers. After an eight hour fast each subject ingested a standardised meal of 95.7 MJ (400 kcal). One hour later 10 ml of one of the two antacids previously labelled with 99mTc was administered. Serial detection by anterior and posterior projection of the amount of antacid retained in the stomach was performed to determine gastric emptying of antacid. One week later the study was repeated under the same conditions with the other antacid also labelled with 99mTc. The mean (SD) percentages of antacid retained in the stomach fit a linear model with a t1/2 of 86.6 (15.3) minutes for magaldrate and 52.3 (5.2) minutes for Maalox (p less than 0.01). When the mean percentages of retention at six time intervals were compared for both antacids, it was found that Maalox emptied much faster (p less than 0.01 at 15 and 30 minutes, p less than 0.02 at 45, 60, 75, and 90 minutes).

Bioavailability of magnesium in beef cattle fed magnesium oxide or magnesium hydroxide

Two experiments were conducted to compare Mg bioavailability from Mg oxide (MgO) vs Mg hydroxide (Mg(OH)2) fed in either a completely mixed diet or a mineral supplement. In Exp. 1, these Mg sources were incorporated into completely mixed diets and offered to 15 steers (282 kg) allotted to three treatments: control diet containing .19% Mg, control plus .2% added Mg as MgO, or control plus .2% added Mg as Mg(OH)2. Each calf was fed 5 kg/d of the respective diet during 10-d adjustment and 7-d collection periods. Blood samples were collected on d 1, 3 and 7. Mg supplementation increased (P less than .01) fecal and urinary Mg excretions, whereas apparent Mg absorption (%) and retention were similar (P greater than .10) for all treatments. Plasma Mg concentrations were similar (P less than .10) for calves supplemented with MgO and Mg(OH)2 but were higher (P less than .05) for Mg supplemented than for control calves on d 7. In Exp. 2, these Mg sources were incorporated into mineral supplements and offered free choice to 30 spring-calving beef cows gazing tetany-inducing pastures from March 6 to May 1. Each of three groups of 10 cows was assigned to a 5.7-ha tall fescue pasture and offered either a control supplement or a supplement containing 40% MgO or Mg(OH)2. Blood samplers were collected on d 0, 7, 14, 28, 42 and 56. Plasma Mg concentrations were not different (P greater than .10) for cows offered MgO and Mg(OH)2 but were higher (P less than .01) for Mg-supplemented than for control cows on d 28, 42 and 56.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in plasma and tissue aluminum concentrations due to different aluminum-containing drugs in patients with renal insufficiency and with normal renal function

The gastrointestinal absorption of aluminum from orally administered aluminum-containing drugs is well documented. Retention of the absorbed aluminum leads to elevated levels of this metal in the tissue of patients with renal failure. We studied two groups of dialysis patients who had received equal amounts of the different aluminum-containing phosphate-binders Aludrox and Antiphosphat. It has recently been shown that Antiphosphat releases only a few aluminum ions in an environment of low pH. Consistent with this finding, we found the aluminum levels to be significantly higher in the plasma, bone, and hair of patients who had received Aludrox as phosphate binder. Subjects with normal renal function excreted most of the ingested and absorbed aluminum. No data are available concerning the tissue load of the element in these subjects. We studied two groups of patients with normal renal function who had received antacid drugs prior to neurosurgery on a brain tumor. The first group of patients were treated with an aluminum-rich antacid (Maalox 70); the other group received an aluminum-poor drug (magaldrate) for 10 days prior to the operation. Analysis of the brain-tissue removed revealed twofold higher aluminum levels in the patients who had received Maalox 70. These results indicate that administration of aluminum-containing drugs leads to a tissue load of aluminum in patients with an impaired renal function as well as in those with a normal function. The extent of the aluminum load depends on the aluminum content and the liberation rate of the drug.

Absorption studies of the H2-blocker nizatidine

The absolute and relative bioavailability of nizatidine, an H2-blocker, was studied in healthy male volunteers. The absolute oral bioavailability, relative to that after intravenous administration, was 98% +/- 14%. The bioavailability of single and multiple oral doses of 150 mg nizatidine was unaffected by concurrent food ingestion; nizatidine may be administered either with or without food. The relative bioavailability of nizatidine was compared when given simultaneously with placebo or Gelusil, 30 minutes after propantheline, or 60 minutes before activated charcoal. Gelusil reduced the amount of nizatidine absorbed by about 10%, charcoal reduced it by about 30%, and propantheline did not affect it.