Aluminum Magnesium Hydroxide Research Articles

Evaluation of phenomena occurring during the preparation of matrix granules by the hot melt technique

The aim of this study was to evaluate the applicability of hot melt granulation for the formulation of a pH-sensitive intelligent tablet containing heat- and moisture-sensitive components. An appropriate combination of magnesium trisilicate, aluminium hydroxide, sodium bicarbonate, and basic butylated methacrylate copolymer (Eudragit E PO) exhibited a good disintegration profile, but poor processibility. Hot melt granulation was applied with the aid of polyethylene glycol 2000 to increase the tablettability. The effects of the composition and the process on the properties of the granules and tablets formed were assessed with thermoanalytical and conventional testing methods. The heating of mixtures containing basic butylated methacrylate copolymer (Eudragit E PO) below its glass transition caused a relevant change in the wettability of the granules. This was induced by an alteration in the microstructure of the agglomerates. Tablets prepared from the granules containing an appropriate ratio of polymers exhibited an appropriate mechanical and disintegration profile. The thermal behaviour of the mixture of polymers cannot be predicted from the properties of the starting materials. Their interaction, demonstrated by DSC, can cause significant structure-forming problems in the matrices. The parameters of the granules and tablets varied with the quantity of the polymer applied. With an appropriate combination of polymers, hot melt granulation can be a suitable method for the preparation of intermediates for the formulation of controlled-release antacid tablets. Thermal analysis can promote an understanding of the process and determination of its operational parameters.

Mechanochemisitry Synthesis of Al-Rich Layered Double Hydroxides

In present work mechanochemical synthesis of fine dispersed MgAl-CO3 LDHs is based on the preliminary mechanical activation of mixture of magnesium hydroxide, aluminium hydroxide and sodium hydrogen carbonate in a planetary activator AGO-2, followed by the thermal treatment of activation products at a temperature of 90 . The Mg/Al molar ratio was discussed. The samples were characterized by x-ray diffraction, thermogravimetry, scanning electron microscope, and energy dispersive spectrometer. According to obtained data the interaction mechanism was proposed.

Determination of Chemical Homogeneity of Fire Retardant Polymeric Nanocomposite Materials by Near-Infrared Multispectral Imaging Microscopy

Polymer nanocomposites containing layered double hydroxide (LDH) additives offer great potential for improving polymer physical properties. Of particular interest is the possibility of improving the fire retardancy and thermal stability of polymers using low loadings of this emerging class of nano-additives. Understanding the relationship between the quality of additive dispersion in the polymer matrix (i.e., chemical homogeneity) and selected flammability properties is a key question for optimizing LDHs for use in fire retardant formulations. We have demonstrated, for the first time, that the near infrared multispectral imaging (NIR-MSI) microscope can be successfully used to characterize the chemical homogeneity of a model system containing a magnesium aluminum hydroxide LDH modified with interlayer undecenoate anions mixed with poly(ethylene). The NIR-MSI is suited for this task because it can simultaneously record spectral and spatial information of a sample with high sensitivity (single pixel resolution) and high spatial resolution (∼0.9 μm/pixel). At 20% added, LDH was found to distributed inhomogeneously in a poly(ethylene) nanocomposite sample on the micron scale.

Flame retardance and mechanical properties of a polyamide 6/polyethylene/surface‐modified metal hydroxide ternary composite via a master‐batch method

AbstractSurface‐modified aluminum hydroxide and magnesium hydroxide mixtures (SAMHs) were filled with linear low‐density polyethylene (LLDPE) with a maleic anhydride grafted polyethylene (PE) compatibilizer to produce a SAMH master batch, which was then dispersed in polyamide 6 (PA6) to yield a PA6/PE/SAMH (50/20/30 by weight ratio) ternary composite. Through such a master‐batch method, an effective flame retardance UL94 V‐0 rating at a 3.2 mm thickness with a 33% limiting oxygen index was achieved. The flame‐retardance mechanism of the ternary composite was investigated by thermogravimetric analysis and scanning electron microscopy/energy dispersive X‐ray spectroscopy analysis. A cocontinuous PA6/PE polymer host and a preferential dispersion of SAMH particles in the matrix induced the formation of a compact flame‐resistant char layer and a high residue rate during burning; this resulted in the desired flame retardance of the ternary composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Cross-linked poly(ethylene vinyl acetate) (EVA)/low density polyethylene (LDPE)/metal hydroxides composites for wire and cable applications

Formulations of chemically cross-linked poly(ethylene vinyl acetate) (EVA) and low density polyethylene (LDPE) blends containing metal hydroxides flame retardants such as aluminum hydroxide (ATH) and magnesium hydroxide (MH) were prepared. Comparison of both type of metal hydroxides in respect of their influence on flammability as well as mechanical, thermal, and electrical properties of EVA/LDPE composites is presented. Most of the investigated properties are better for composites containing MH in comparison with composites containing ATH. Influence of various EVA/LDPE ratios on investigated properties is presented as well. Importance of improving compatibility using compatibilizers to improve some of the investigated properties is described. Polyethylene grafted with maleic anhydride (PEgMA) was found to be better compatibilizer for ATH than vinyl silanes.

Invitro evaluation of the neutralising capacity of twenty brands of antacids in Lagos, Nigeria

The use of substandard drugs is a great threat to the lives of people in the community. Identification of substandard drugs is important to exclude their use in clinical practice. These drugs may lead to reduced efficacy of pharmacotherapy. Antacid preparations are weakly basic and consist of metal salts, most commonly aluminium hydroxide or magnesium hydroxide. These salts dissociate to neutralise gastric acid and form neutral salts. The ultimate goal of antacid therapy is to reduce the concentration and the total load of acid in gastric juice with a pH of 1.3 to a pH between 3.5 and 5.0. The aim of this work is to carry out an in-vitro test on the acid neutralising capacity (ANC) of commonly available antacid brands in Lagos market. The British pharmacopoeia (BP) method of analysis of antacids was adopted. Twenty different brands of antacid suspensions and tablets were analysed. Brand SH suspension gave the highest neutralising capacity, 101.65 ml +/- 0.15, while brand SN gave the lowest, 99.75 ml +/- 0.75. All the fourteen antacid suspensions analysed complied with the official specification and therefore passed the analysis. Brand TB tablet gave the highest acid neutralising capacity (ANC), 54.10 ml +/- 0.2 while brand TD 49.50 ml +/- 0.1 gave the lowest. All the six antacid tablet brands analysed passed the assay. The ANC of an antacid is a parameter used to measure the effectiveness of an antacid in relieving ulcer pain. The acid-neutralising capacity of the antacid brands analysed were within the BP specification. The acid neutralising capacity of antacids should be determined before administration.

Effects of nanoclay and fire retardants on fire retardancy of a polymer blend of EVA and LDPE

The effects of nanoclay (organoclay) and fire retardants (aluminium tri-hydroxide and magnesium hydroxide) on the fire retardancy of a polymer blend of ethylene-vinyl acetate (EVA) and low-density polyethylene (LDPE) were assessed using thermogravimetric analysis (TGA) and the cone calorimeter. TGA measurements were conducted in nitrogen and air atmospheres at different heating rates (1–20 °C/min), whilst in the cone calorimeter square samples were tested under various external heat fluxes (15–60 kW/m 2). The TGA results indicate that the nanoclay (NC) alone has little effect on the degradation of the polymer blend, whereas aluminium tri-hydroxide (ATH) and magnesium hydroxide (MH), used as fire retardants (FRs), generally decrease the onset degradation temperature and also reduce the peak mass loss rate. However, it was found in the cone calorimeter that, though having negligible effect on ignition, the nanoclay reduces the heat release rate (HRR), and increases smoke and CO yields. In comparison, FRs (ATH or MH) were found to delay ignition owing to loss of water at lower temperatures, reduce the HRR, and have similar smoke and CO yields compared to the polymer blend. The reduced HRRs for both the nanoclay and FRs can be attributed to the formation of a surface layer (a nano layer for nanoclay and a ceramic-like layer of Al 2O 3/MgO for FRs), which acts as mass and heat barriers to the unpyrolysed material underneath. The global effect of the surface layer for the polymer blend nanocomposite was examined using a previously developed numerical model, and a methodology for predicting the mass loss rate was subsequently developed and validated.

Flame retardancy effect of surface-modified metal hydroxides on linear low density polyethylene

Metal hydroxides (MAH) consisting of magnesium hydroxide and aluminum hydroxide with a mass ratio of 1:2 were surface-modified by γ-diethoxyphosphorous ester propyldiethoxymethylsilane, boric acid and diphenylsilanediol in xylene under dibutyl tin dilaurate catalyst at 140 °C. Phosphorus, silicon and boron elements covalently bonded to metal hydroxide particles were detected by X-ray photoelectron spectroscopy. The degradation behavior of the surface-modified MAH was characterized by thermogravimetric analysis. The results show that linear low density polyethylene (LLDPE) composite, filled with 50% (mass fraction) of MAH modified by 5.0% (mass fraction) of modifiers, passes the V-0 rating of UL-94 test and shows the limited oxygen index of 34%, and its heat release rate and average effective heat combustion in a cone calorimeter measurement decrease obviously; The mechanical properties of MAH can be improved by surface-modification. The uniform dispersion of particles and strong interfacial bonding between particles and matrix are obtained.

Application of Nanometer Aluminum Magnesium Hydroxide in PVDF Membrane Modification

In this article, we adopted the phase inversion process to prepare nanometer aluminum magnesium hydroxide/PVDF hybrid membrane, studied the influences of nanometer materials on pure water flux, retention, pore diameter, porosity, microstructure, mechanical property and adsorption property for membranes, researched the influences of different AMH contents on membrane property, and analyzed element contents of membrane transect through x-radial energy dispersive analysis (EDS). Comparing with PVDF membrane without nanometer materials, the results indicated that the addition of nanometer materials obviously enhanced the pure water flux, retention, microstructure, mechanical property and adsorption property for membranes, and didn’t largely influence the pore diameter and porosity for membranes. The analysis of SEM indicated that the addition of nanometer materials could obviously change the microstructure of membrane.

Comparison of Aluminium Hydroxide and Magnesium Hydroxide as Flame Retardants in Sebs-Based Composites

The flame retardancy and mechanical properties of styrene-ethylene/butylene-styrene block copolymer (SEBS) based composites, containing paraffinic hydrocarbon extender oil filled SEBS (O-SEBS), blended with copolymer polypropylene (PP), and flame-retardant filler aluminium hydroxide (ATH) or magnesium hydroxide (MH) were investigated. Limiting Oxygen Index (LOI) values of both ATH and MH filled composites increased substantially as the amount of ATH and MH increased, respectively. Furthermore, the LOI values of the ATH system are higher than those of MH for the same addition level. When MH is introduced, progressively, into ATH-filled composites, and for a constant combined filler loading of 65 wt.%, LOI only decreases, when the ratio of MH to ATH exceeds 40%. Combining the two retardants, in the composites, may have a synergistic effect with respect to fire retardance. Tensile strength, up to 50 wt.% filler, and elongation at break of the composites decrease as the amount of filler increases. However, the elongation at break of the composites filled with MH is a little higher than that with ATH, but for tensile strength there is little difference between them. At filler loading greater than 50 wt.%, the tensile strength levels off but the% elongation is dramatically reduced. Introduction of MH in ATH filled composites leads to some variation in the mechanical properties of the composites. For a combined filler loading of 65 wt.%, the elongation at break increases from around 180 to 200% for a progressive increase in the ratio of MH to ATH up to 40% and there is a large increase in% elongation to around 300% when MH ratio reaches 55–60%, thereafter the% elongation falls. This effect may be linked to particle size distribution of the respective MH and ATH fillers. In contrast, there is little effect on the tensile strength. The thermogravimetric analysis (TGA) and differential TG (DTG) data show that ATH and MH increase the thermal stability of the SEBS-based composites.

The study of the conversion of intercalated compounds synthesized from a sol-gel procedure

Intercalated materials containing iron and carbonate species were synthesized in this work to study their hydrolysis and condensation from sol to gel transition. The former material was designated as PV (perovskite) and the latter HT (hydrotalcite). Another sample containing neither of the indicated ions was designated as AlMg(OH)5 (aluminum magnesium hydroxide). The conversion energy of these materials for the hydrolysis and condensation reaction during the transition was estimated to be ≈14 cal/mol, much lower than the hydration energy of 10–14 kcal/mol computed using molecular dynamic simulation from the previous work. The energy consumed was interpreted as equivalent to the drop of temperature due to the endothermic reaction. PV material exhibited the highest swelling ratio, amounting to 76% from its dried weight, demonstrating its ability to intercalate water readily. HT sample, on the other hand, was completely saturated and did not dilate.

Enhancing the Immune Response

Although aluminum-containing adjuvants are widely used in vaccines, the mechanisms whereby they potentiate the immune response have been unclear. Various agents with adjuvant activity stimulate maturation of dendritic cells (DCs), which are critical to activating adaptive immune responses; however, in vitro studies have not found any effect of aluminum-containing adjuvants on DC maturation. Kool et al . used mice that had received fluorescently labeled T cells that recognized ovalbumin (OVA) to establish that OVA emulsified with a suspension of aluminum hydroxide and magnesium hydroxide (OVA-alum) elicited a larger and more prolonged immune response than did OVA alone. Intraperitoneal (i.p.) injection of OVA-alum stimulated the rapid recruitment to the peritoneal cavity of inflammatory monocytes as well as a later increase in myeloid and plasmacytoid DCs, neutrophils, and eosinophils. OVA-alum stimulated more OVA uptake and processing by peritoneal CD11c + DCs than did OVA. Further, it stimulated DC maturation, ability to stimulate T cell proliferation, and migration to draining lymph nodes. Indeed, OVA-alum stimulated OVA uptake by inflammatory monocytes and their stimulation of T cell proliferation, as well as their migration to draining lymph nodes, expression of CD11c, and conversion to DCs. Depletion of DCs resident in specific lymph nodes abolished stimulation of T cell proliferation in those nodes by i.p. OVA, but not OVA-alum, whereas systemic depletion of CD11c + cells during immunization abolished OVA-alum’s adjuvant activity. Unlike saline or OVA, i.p. injection of OVA-alum increased peritoneal uric acid concentration. Uricase abolished OVA-alum–dependent recruitment of inflammatory monocytes to lymph nodes (also lost in mice lacking MyD88, which has been implicated in the inflammatory response to uric acid) and its adjuvant effect. The authors thus conclude that the immunostimulatory activity of aluminum-containing adjuvants depends on activation of DCs by uric acid. M. Kool, T. Soullié, M. van Nimwegen, M. A. M. Willart, F. Muskens, S. Jung, H. C. Hoogsteden, H. Hammad, B. N. Lambrecht, Alum adjuvant boosts adaptive immunity by inducing uric acid and activating inflammatory dendritic cells. J. Exp. Med. 205 , 869-882 (2008). [Abstract] [Full Text]

The effect of a combination antacid preparation containing aluminium hydroxide and magnesium hydroxide on rosuvastatin pharmacokinetics

ABSTRACTObjective: Rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor used for the treatment of dyslipidaemia, may be co-administered with antacids in clinical practice. This trial assessed the effect of simultaneous and separated administration of an antacid preparation containing aluminium hydroxide 220 mg/5 mL and magnesium hydroxide 195 mg/5 mL (co-magaldrox 195/220) on the pharmacokinetics of rosuvastatin.Research design and methods: A randomised, open-label, three-way crossover trial was performed. Healthy male volunteers (n = 14) received a single dose of rosuvastatin 40 mg alone, rosuvastatin 40 mg plus 20 mL antacid suspension taken simultaneously, and rosuvastatin 40 mg plus 20 mL antacid suspension taken 2 h after rosuvastatin on three separate occasions with a washout of ≥ 7 days between each.Main outcome measures: The primary parameters were area under the rosuvastatin plasma concentration–time curve from time zero to the last quantifiable concentration (AUC(0–t)) and maximum observed rosuvastatin plasma concentration (Cmax) in the absence and presence of antacid.Results: When rosuvastatin and antacid were given simultaneously, the antacid reduced the rosuvastatin AUC(0–t) by 54% (90% confidence interval [CI] for the treatment 0.40–0.53) and Cmax by 50% (90% CI 0.41–0.60). When the antacid was given 2 h after rosuvastatin, the antacid reduced the rosuvastatin AUC(0–t) by 22% (90% CI 0.68–0.90) and the Cmax by 16% (90% CI 0.70–1.01). The effect of repeated antacid administration was not studied and it cannot be discounted that this may have resulted in a stronger interaction than that observed here.Conclusions: Simultaneous dosing with rosuvastatin and antacid resulted in a decrease in rosuvastatin systemic exposure of approximately 50%. This effect was mitigated when antacid was administered 2 h after rosuvastatin.

Mechanochemical synthesis of a hydroxycarbonate form of layered magnesium aluminum hydroxides

Mechanical activation of a mixture of magnesium hydroxide, aluminum hydroxide, and sodium bicarbonate in an AGO-2 planetary mill, followed by water washing leads to the formation of a layered magnesium aluminum hydroxide. The double hydroxide obtained at a magnesium hydroxide to aluminum hydroxide ratio of 3:1 is essentially phase-pure and contains both carbonate and bicarbonate ions in its interlayer spaces. The synthesized double hydroxide was characterized by x-ray diffraction, IR spectroscopy, thermogravimetry, differential thermal analysis, and chemical analysis.

A Randomized Controlled Trial Comparing Treatment Regimens for Acute Pain for Topical Oleoresin Capsaicin (Pepper Spray) Exposure in Adult Volunteers

Objective. Several topical therapies have been proposed to treat acute pain from exposure to oleoresin capsaicin (OC). The purpose of this study was to determine the most beneficial topical treatment for relieving contact dermatitis pain caused by OC exposure. Methods. We performed a single-blind, randomized human experiment evaluating the effectiveness of five different regimens for the treatment of topical facial OC exposure. Forty-nine volunteer, adult law enforcement trainees were exposed to OC during a routine training exercise andwere randomized to one of five treatment groups (aluminum hydroxide–magnesium hydroxide [Maalox], 2% lidocaine gel, baby shampoo, milk, or water). After initial self-decontamination with water, subjects rated their pain using a 10-cm visual analog scale (VAS) andthen every 10 minutes, for a total of 60 minutes. Subjects were blinded to previous VAS recordings. A two-factor analysis of variance (ANOVA) (treatment, time) with repeated measures on one factor (time) was performed using a 1.3-cm difference as clinically significant. Results. Forty-four men andfive women, with an average age of 24 years, participated in the study. There was a significant difference in pain with respect to time (p < 0.001), but no significant interaction between time andtreatment (p > 0.05). There was no significant difference in pain between treatment groups (p > 0.05). Conclusion. In this study, there was no significant difference in pain relief provided by five different treatment regimens. Time after exposure appeared to be the best predictor for decrease in pain.

Cerâmicas porosas para aplicação em altas temperaturas

Com o objetivo de reduzir o consumo energético, tem crescido o uso de cerâmicas refratárias porosas como isolantes térmicos para altas temperaturas. Entre as técnicas comumente empregadas na produção desses materiais (como a adição de surfactante e incorporação de orgânicos), destaca-se aquela baseada na geração de poros por meio de transformações de fase. Comparada às outras técnicas, esse processo se mostra bastante simples e sem geração de voláteis tóxicos. Neste trabalho, essa técnica foi utilizada para produzir porosos por meio da decomposição de hidróxidos de alumínio e alumínio-magnésio, e da posterior reação de espinelização, que os estabiliza e impede sua densificação acima de 1000 ºC. Verificou-se que o uso de hidróxidos complexos resulta em maior volume de poros, resistência mecânica e refratariedade que sua utilização isolada.

Sorption of radioiodine from aqueous solutions on layered double magnesium aluminum hydroxides at 300 K

Sorption of 131I− and 131IO 3 − from aqueous solutions at 300 K on solid layered double magnesium aluminum hydroxides (Mg-Al-LDH) in the carbonate (Mg-Al-LDH-CO3) and nitrate (Mg-Al-LDH-NO3) forms was studied. The distribution coefficients of 131I− and 131IO 3 − between solid Mg-Al-LDH-CO3 and an aqueous solution after contact of these phases for 60 min are 38 and 34 ml g−1, respectively. The distribution coefficients of 131I− and 131IO 3 − between solid Mg-Al-LDH-NO3 and an aqueous solution, measured under the similar conditions, are about 5 ml g−1. After contact of the solid and liquid phases for 14 h, the distribution coefficients of 131I− and 131IO 3 − between an aqueous phase and solid layered double magnesium aluminum oxides (Mg-Al-LDO) prepared by thermolysis of Mg-Al-LDH are 7999 and 7068 ml g−1, respectively.

Template formation of aluminum–magnesium hydroxide nano-branches on linear poly(ethylene imine)

Linear poly(ethylene imine) (PEI) can self-assemble into fibrous aggregates composed of a crystalline core and a brush-like shell of ethylene imine (EI) segments, and thus can be used as “templates” to prepare a range of inorganic materials. To further illustrate the feasibility of this technique, an investigation of low-temperature formation of nanostructured aluminum–magnesium hydroxide (AMH) on linear PEI “templates” is described, and the corresponding reaction mechanism suggested tentatively. AMH nano-branches were formed after hydrolysis of aluminium and magnesium lactates on PEI, indicating the site-selective deposition process of AMH on surfaces of PEI. The technique reported in this paper could be potentially used to fabricate other nanostructured complex metal oxides.

Radiation-induced esophagitis: A double-blind randomized clinical trial of aluminum hydroxide plus magnesium hydroxide plus oxetacaine suspension versus aluminum hydroxide plus magnesium hydroxide suspension

9100 Background: To assess whether oral administered oxetacaine-containing suspension is effective in treating acute radiation- induced esophagitis in cancer patients. Methods: A double-blind, prospective-randomized clinical trial was conducted across 20 radiotherapy institutions in Germany. Patients [pts.] with head and neck or thoracic cancer without dysphagia/odynophagia received definitive or postoperative radiotherapy [RT] with or without chemotherapy including at least 5 cm of the esophagus in the high dose volume. Pts. were randomized to receive oral aluminum hydroxide plus magnesium hydroxide plus oxetacaine (Tepilta [T]) suspension or aluminum hydroxide plus magnesium hydroxide suspension without oxetacaine (Magaldrat [M]) as first-line treatment for acute radiation-induced esophagitis. Primary endpoint was the interval between begin of RT and failure of first-line treatment of esophagitis defined as need for additional systemic analgesics. Data on pts.’ symptoms were collected during and for at least 2 weeks after treatment. Results: A total of 158 pts. were randomized, of whom 103 had take at least one dose of the study medication for acute esophagitis = grade 2 (CTC). Of the 105 pts., 51 were randomized to receive T and 52 M. The cumulative incidence of acute esophagitis = grade 2 (CTC) was 25% for the T and 22% for the M arm. Kaplan-Meier analysis showed a statistically significant difference between the two groups regarding the need for systemic analgesics under consideration of the intake time in favor of T (p = 0.032). No statistically significant difference was found between the two groups regarding the secondary endpoints need respective delay of additional parenteral nutrition (p = 0.28 respective p = 0.12), and pts.`s and investigator`s estimation of global effectivity of the study medication (0.08 and 0.12). Conclusions: This trial demonstrated a statistically significant delay of the intake time for systemic analgesics in pts. randomized to receive oral aluminum hydroxide plus magnesium hydroxide plus oxetacaine suspension. No significant financial relationships to disclose.

Clinical Pharmacokinetics and Gastrointestinal Tolerability of a Novel Extended-Release Microsphere Formulation of Azithromycin

A novel oral, extended-release, microsphere formulation of azithromycin (AZSR) was developed to improve the gastrointestinal tolerability profile while allowing administration of an entire treatment course of azithromycin in a single dose. Several phase I clinical pharmacology studies were conducted to (i) identify a well-tolerated single-dose formulation that met a predefined exposure target; and (ii) evaluate the effect of food and antacid on the absorption of this formulation. Of these, five pivotal studies are described here. The pharmacokinetic profile of AZSR was compared with that of the commercially available immediate-release azithromycin formulation (AZM) in an open-label, crossover, single-dose study (Study A), and their gastrointestinal tolerability profiles were compared in an observer-blind, parallel group, single-dose study (Study B). The effects of food (a high-fat meal and a standard meal) and antacid (a single 20 mL dose of Maalox Regular Strength, containing magnesium hydroxide, aluminium hydroxide and simethicone) on the absorption of azithromycin from AZSR were evaluated in three separate open-label, crossover, single-dose studies (Studies C, D and E). Healthy adult subjects were enrolled in all five studies, and all subjects were evaluable for tolerability. The dose used for all azithromycin formulations was 2.0 g. Serum azithromycin concentrations were determined using a validated high-performance liquid chromatography/electrochemical detection method, and pharmacokinetic parameters were analysed using noncompartmental methods. 377 subjects received a single 2.0 g dose of azithromycin as AZSR and/or AZM in the five studies. Compared with AZM, AZSR had a slower absorption rate (57% decrease in the mean peak concentration [C(max)] and an approximate 2.5-hour delay in the time to reach C(max) [t(max)]), with a mean relative bioavailability of 82.8%, which met the predefined exposure target (at least 80% bioavailability relative to AZM). Compared with AZM, AZSR was associated with significantly lower rates of nausea and vomiting. A high-fat meal increased the mean area under the serum concentration-time curve [AUC] from time zero to 72 hours post-dose (AUC(72 h)) by 23% and increased the C(max) of azithromycin by 115%. A standard meal increased the mean C(max) by 119% but had no clinically significant effect on the AUC(72 h). AZSR appeared to be better tolerated in the fasted state than in the fed state. The AUC(72 h) and C(max) of AZSR were not significantly affected by co-administration with a single dose of antacid. The extended-release microsphere formulation of azithromycin, AZSR, allows administration of an entire therapeutic course of azithromycin as a well-tolerated single 2.0 g dose. This formulation should be administered on an empty stomach and can be co-administered with antacids.