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Biomedical subjects

G A Brazeau

Publications and source records attributed to G A Brazeau.

At least 19 recordsLinked to original sources
PubMed2001

Myotoxicity studies of injectable biodegradable in-situ forming drug delivery systems.

The objective of the study was to investigate the potential in-vitro and in-vivo myotoxicity of different in-situ forming biodegradable drug delivery systems, namely in-situ Microparticle (ISM) systems and polymer solutions (in-situ implant systems). The acute myotoxicity was evaluated in-vitro using the isolated rodent skeletal muscle model by measuring the cumulative creatine kinase (CK) efflux. For the in-vivo study, following intramuscular injection (i.m.) into male Sprague Dawley rats, the area under the plasma CK-curve was used to evaluate muscle damage. The formulations included ISM-systems [a poly (lactide)-solvent phase dispersed into an external oil phase] and poly (lactide) solutions (in-situ implant systems). Phenytoin and normal saline served as positive and negative controls, respectively. Poly (lactide) in different solvents (in-situ implant systems) resulted in 14.4-24.3 times higher CK-values compared to normal saline, indicating a high myotoxic potential. With the ISM-system, the CK-release was significantly lower, decreased with a lower polymer phase: oil phase ratio, and approached the values of normal saline at a ratio of 1:4. Bupivacaine HCl- and Buserelin acetate- containing ISM-systems resulted in significantly lower CK-levels when compared to the corresponding drug formulation in normal saline. The in-vivo studies confirmed the in-vitro data and showed good muscle compatibility of the ISM-systems.

Animals↗
PubMed2001

Clinical pharmacology of the dietary supplement creatine monohydrate.

Creatine is a dietary supplement purported to improve exercise performance and increase fat-free mass. Recent research on creatine has demonstrated positive therapeutic results in various clinical applications. The purpose of this review is to focus on the clinical pharmacology and therapeutic application of creatine supplementation. Creatine is a naturally occurring compound obtained in humans from endogenous production and consumption through the diet. When supplemented with exogenous creatine, intramuscular and cerebral stores of creatine and its phosphorylated form, phosphocreatine, become elevated. The increase of these stores can offer therapeutic benefits by preventing ATP depletion, stimulating protein synthesis or reducing protein degradation, and stabilizing biological membranes. Evidence from the exercise literature has shown athletes benefit from supplementation by increasing muscular force and power, reducing fatigue in repeated bout activities, and increasing muscle mass. These benefits have been applied to disease models of Huntington's, Parkinson's, Duchenne muscular dystrophy, and applied clinically in patients with gyrate atrophy, various neuromuscular disorders, McArdle's disease, and congestive heart failure. This review covers the basics of creatine synthesis and transport, proposed mechanisms of action, pharmacokinetics of exogenous creatine administration, creatine use in disease models, side effects associated with use, and issues on product quality.

Animals↗
PubMed2000

Protective effect of estrogens against oxidative damage to heart and skeletal muscle in vivo and in vitro.

Estrogen has been shown to protect skeletal muscle from damage and to exert antioxidant properties. The purpose of the present study was to investigate the antioxidant and protective properties of estrogens in rodent cardiac and skeletal muscle and H9c2 cells. Female Sprague-Dawley rats were separated into three groups, ovariectomized (OVX), ovariectomized with estrogen replacement (OVX + E2), and intact control (SHAM), and were assessed at two time periods, 4 and 8 weeks. Rodents hearts were analyzed for basal and iron-stimulated lipid peroxidation in the absence and presence of beta-estradiol (betaE2) by measuring thiobarbituric acid reactive species (TBARS). Isolated soleus (SOL) and extensor digitorum longus (EDL) were analyzed for creatine kinase (CK) efflux. Using H9c2 cells, the in vitro effects of betaE2 and its isomer alpha-estradiol were investigated under glucose-free/hypoxic conditions. TBARS assay was also performed on the H9c2 in the presence or absence of betaE2. The results indicate that OVX rodent hearts are more susceptible to lipid peroxidation than OVX + E2 hearts. OVX soleus showed higher cumulative efflux of CK than OVX + E2. Furthermore, H9c2 survival during oxidative stress was enhanced when estrogen was present, and both OVX hearts at 4 weeks and H9c2 cells particularly were protected from oxidative damage by estrogens. We conclude that estrogen protects both skeletal and cardiac muscle from damage, and its antioxidant activity can contribute to this protection.

Animals↗
PubMed2000

Assessment of the myotoxicity of pharmaceutical buffers using an in vitro muscle model: effect of pH, capacity, tonicity, and buffer type.

The purpose of the present study was to investigate the myotoxicity of three buffers containing carboxylic acid groups (i.e., acetate, succinate, and citrate) as a function of their pH, capacity, and tonicity. The myotoxicity of these buffers in the range of pH 2-6 and 0.001-0.1 M buffer capacity was assessed using cumulative creatine kinase (CK) release from an isolated rodent muscle model following injection. Phenytoin and 0.9% NaCl injection were used as positive and negative controls, respectively. Buffer solutions were prepared. A lower pH and higher buffer capacity was linked to increased myotoxicity for the acetate buffers. However, for succinate and citrate buffers, pH appeared to influence the extent of myotoxicity, whereas buffer capacity did not seem to have an effect. When either NaCl or trehalose was used as a tonicity-adjusting agent at pH 6, isotonic 0.01 M buffer solutions dramatically lowered the cumulative CK release compared to those that were not isotonic. Isotonic succinate buffers displayed the lowest myotoxicity, whereas citrate buffers displayed the highest values. Citrate buffers containing three carboxylic acid groups showed higher myotoxicity than succinate buffers and acetate buffers at 0.001 and 0.01 M buffer capacities, whereas acetate buffer produced higher cumulative CK release than citrate and succinate buffers at 0.1 M buffer capacity. The myotoxicity of pharmaceutical buffers containing carboxylic acid groups appears to be directly affected by lowering the pH of the solution.

Acetates↗
PubMed2000

In situ gel formulations for gene delivery: release and myotoxicity studies.

The in vitro release of plasmid DNA and salmon sperm DNA from in situ gel formulations was investigated. Two in situ gel systems were studied: (a) an interpolymeric complex (IPC) of water-soluble polymers polymethacrylic acid (PMA) and polyethylene glycol (PEG) and (b) a hydroxypropylmethylcellulose-carbopol system (H:C). Two-way analysis of variance with replication demonstrated that both gel composition and medium pH influenced significantly the release of plasmid DNA from in situ gel formulations. When the release of both types of DNA was compared, higher release was observed for plasmid DNA compared to genomic salmon sperm DNA. Conformational analysis of the released plasmid DNA showed that DNA was released without degradation, but with remarkable conversion from supercoiled (SC) to open circular (OC). In addition, the tested in situ gel systems demonstrated protection from DNAse I degradation. The myotoxicity of the injectable gelling solutions was assessed by the cumulative release of creatine kinase (CK) over 120 min from the isolated rodent extensor digitorum longus (EDL) muscle. A higher level of cumulative CK was observed for IPC when compared to H:C (2:1). These results demonstrate that the in situ gelling systems can be considered as a valuable injectable controlled-delivery system for pDNA in their role to provide protection from DNAse degradation.

Animals↗
PubMed1998

Current perspectives on pain upon injection of drugs.

A limitation in the administration of parenteral products is the pain caused upon injection. Injection site pain has been predominately associated with intravenous, intramuscular, and subcutaneous administration. It becomes important for the formulation scientist to have a basic understanding of the physiology underlying the pain process, as well as the pharmaceutical factors associated with injection site pain. Initially, this review will provide the reader with a primer on the mediation of pain in the periphery and a compilation of those drugs that have been associated with pain on injection. In addition, this review will present important considerations and general formulation approaches or methods that have been used to overcome pain on injection. Finally, a brief overview of the various experimental systems used to investigate injection site pain is discussed.

Humans↗
PubMed1998

In vitro myotoxicity of selected cationic macromolecules used in non-viral gene delivery.

PURPOSE: Cationic lipid/DNA complexes have been proposed as a method of in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are associated with tissue toxicity at the injection site. Therefore, the objective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro. METHODS: Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longus muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37 degrees C) following a 15 microL injection of the test formulation. Phenytoin (Dilantin) and normal saline served as positive and negative controls, respectively. RESULTS: The myotoxicity of plasmid DNA (pDNA, approximately 5000bp, 1 mg/ml) was not statistically different from normal saline. However, the myotoxicity of Dilantin was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polylysine's myotoxicity was found to be dependent upon concentration and molecular weight. The myotoxicity of formulations of cationic liposomes(s), lower molecular weight polylysine (25,000) and higher concentration of PAMAM dendrimers with pDNA were found to be statistically less significant than those formulations without pDNA. CONCLUSIONS: The cationic liposomes were less myotoxic compared to the dendrimers and polylysine. Myotoxicity was dependent upon the type of cationic lipid macromolecule, concentration, molecular weight and the presence of pDNA. A possible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overall positive charge of the injectable system resulting in less damage.

Animals↗
PubMed1996

In vitro-in vivo myotoxicity of intramuscular liposomal formulations.

PURPOSE: The first objective was to study the in vitro myotoxicity of empty liposomes and to examine whether liposome size, charge and fluidity affect of liposomal myotoxicity. The second objective was to investigate the effect of liposomal encapsulation on the in vitro and in vivo myotoxicity of loxapine compared to the loxapine commercial preparation (Loxitane). METHODS: The in vitro myotoxicity of empty liposomes and loxapine liposomes was evaluated by the cumulative efflux of the cytosolic enzyme creatine kinase (CK) from the isolated rat extensor digitorum longus (EDL) muscle over a 2 hour period. In the in vivo studies, the area under plasma CK curve over 12 hours was used to evaluate muscle damage. RESULTS: The in vitro myotoxicity for all empty liposomal formulations was not statistically different from negative controls (untreated control muscles and normal saline injected muscles). However, these empty liposomal formulations were significantly less myotoxic than the positive controls (muscles injected with phenytoin and muscle sliced in half). In vitro-in-vivo studies showed that the liposomal encapsulation of loxapine resulted in significant (P < 0.05) reduction in myotoxicity (80% in vitro and 60% in vivo) compared to the commercially available formulation which contains propylene glycol (70% V/V) and polysorbate 80 (5% W/V) prepared at equal concentration. CONCLUSIONS: Results indicate that empty liposomes do not induce myotoxicity. Furthermore, liposomal size, charge and fluidity do not affect myotoxicity. In addition, in vitro and in vivo studies have demonstrated that liposomal encapsulation of loxapine can reduce myotoxicity compared to a formulation containing organic cosolvents.

Animals↗
PubMed1996

Evaluation of PLGA microsphere size effect on myotoxicity using the isolated rodent skeletal muscle model.

The present work investigated the magnitude of microsphere-induced acute myotoxicity and determined whether this myotoxicity is related to microsphere size and/or reconstitution solvent. Using a high molecular weight poly(dl-lactide-co-glycolide) copolymer, the myotoxicity of two different size microsphere formulations (3.6 microns and 19 microns) in normal saline or distilled water was quantified using a previously validated isolated rat muscle system. Overall, microspheres were found to be relatively nontoxic compared to known myotoxic agents (e.g., phenytoin) and control muscles. The smaller microspheres were found to be significantly more myotoxic than larger microspheres. Furthermore, the myotoxicity was lower in large microspheres reconstituted with normal saline or normal saline with 0.5% (w/v) carboxymethylcellulose (to prevent aggregation) compared to those reconstituted with distilled water. Smaller microspheres were found to be extremely difficult to inject, due to aggregation, which could not be prevented by the addition of carboxymethylcellulose. This study suggests that larger microspheres are less myotoxic than smaller microspheres.

Animals↗
PubMed1995

Effects of cocaine on leakage of creatine kinase from skeletal muscle: in vitro and in vivo studies in mice.

The mechanism of cocaine-induced rhabdomyolysis and/or muscle damage has not been elucidated. To determine if cocaine has a direct effect on muscle, isolated soleus and EDL muscles were incubated in the presence of 1 mM and 0.2 mM cocaine using a pulse and continuous exposure protocol. The release of creatine kinase from the isolated EDL muscle was statistically significant only when muscles were exposed to 1 mM cocaine for a period of 30 minutes. These findings suggest that cocaine-induced creatine kinase release could be mediated by a direct action on the fibers. It is also possible, however, that cocaine-induced muscle damage and creatine kinase release may be mediated via an indirect effect. It is possible that cocaine's vasoconstrictor effects could lead to muscle damage via an ischemia-reperfusion injury leading to free radical formation and lipid peroxidation. This study, therefore, also investigated the possibility that cocaine-induced cytosolic enzyme release may be mediated via the formation of free radicals leading to lipid peroxidation. To test this hypothesis, muscle total glutathione levels, a free radical scavenger, and muscle thiobarbituric acid reactive substances (TBARS), a measurement of lipid peroxidation, were examined following an acute IV cocaine dose in mice. Sedentary BalbC mice were injected with cocaine (40 mg/kg) or normal saline via the tail vein. Creatine kinase levels in serum and total glutathione and TBARS in liver and muscle were determined at 4, 8, and 24 hrs. Serum creatine kinase levels were significantly elevated 5-fold, while TBARS were elevated 100% in the gastrocnemius muscle of cocaine-treated animals at 4 hrs compared to normal saline controls. However, serum creatine kinase levels, total glutathione and TBARS in the gastrocnemius muscle were not statistically different at 8 or 12 hrs; or in the liver and anterior tibialis muscle at 4, 8, or 24 hrs. The present findings suggests that lipid peroxidation may be occurring in skeletal muscle after a single IV cocaine dose in mice.

Animals↗
PubMed1995

Weakness in mouse masticatory muscles by repetitive contractions with forced lengthening.

The etiology of myofascial tenderness and pain of masticatory muscles in humans is difficult to understand. Parafunctional oral habits such as tooth grinding or vigorous chewing are thought to be factors. The objective of this study was to determine if masticatory muscles are susceptible to weakness and injury induced by repetitive, dynamic, forced-lengthening contractions. Results would support the hypothesis that contraction-induced injuries could occur in hyperactive masticatory muscles of humans in response to parafunctional oral habits. Mice were anesthetized and randomly assigned to three groups: non-treated controls, treated by repetitive passive jaw opening, or treated by repetitive isometric tetanic contractions with lengthening by jaw opening. In each treatment group, masticatory muscle injury was evaluated by contractile tension, plasma creatine kinase, and muscle glycogen. Contractile tension was determined at different stimulation frequencies and was significantly decreased 5 min, 4 h, and 72 h after repetitive contraction/lengthening. Plasma creatine kinase was significantly elevated at 4 but not at 72 h post-treatment in mice subjected to repetitive contraction/lengthening. Masticatory muscle glycogen was not significantly different in any groups at 4 or 72 h post-treatment. These results indicate that contraction injuries can be induced in masticatory muscle of mice by forced lengthening contractions which simulate eccentric contractions.

Analysis of Variance↗
PubMed1994

Solvent-dependent influences on skeletal muscle sarcoplasmic reticulum calcium uptake and release.

The organic cosolvents propylene glycol (PG) and polyethylene glycol 400 (PEG 400) have previously been shown to differ in their potential to cause muscle damage following im injection. PG was found to be more myotoxic than PEG 400, with indirect implications of the role of cytosolic calcium in mediating this damage. In the present study, the direct effects of these cosolvents were investigated on the sarcoplasmic reticulum (SR), the major intracellular muscle membrane that mobilizes calcium. The passive permeability of isolated SR microsomal vesicles to calcium was not affected by 5.3 and 10.5% (v/v) PG and PEG 400. At 10.5% (v/v), a concentration of the organic cosolvent that would not be unexpected at the injection site, PEG 400 stimulated calcium uptake by 40 and 140% in longitudinal tubular-derived and terminal cisternal-derived vesicles, respectively, without significantly altering the ATP hydrolytic activity of the calcium pump. The calcium pumping efficiency (Ca2+/ATP coupling ratio) was therefore also enhanced. On the other hand, 10.5% (v/v) PG did not significantly alter either calcium uptake or ATPase activity of the pump. PG stimulated calcium efflux from only the terminal cisternae vesicles via a pathway indicative of the ryanodine-sensitive calcium channel, as demonstrated by inhibition of PG-induced efflux by millimolar Mg2+. These results are consistent with multiple interactions of cosolvents with proteins in the membrane bilayer, with the distinction that the two cosolvents differentially influence the calcium pump and release channel, particularly at the terminal cisternae, where there is rapid change of calcium level during excitation-contraction coupling. These data provide further evidence for the role of calcium in mediating organic cosolvent-induced muscle damage. In addition, they provide a possible explanation for the myoprotective effect of PEG 400 (compared to PG) as a result of increased myoplasmic calcium removal and reduced calcium release.

Adenosine Triphosphate↗
PubMed1993

Roles of liposome composition and temperature in distribution of amphotericin B in serum lipoproteins.

The role of liposome composition and temperature in the distribution of amphotericin B (AmB) with serum lipoproteins and the role of particle charge in AmB transfer to serum lipoproteins were determined. Serum obtained from healthy volunteers was incubated with known concentrations of AmB or different liposomal formulations of AmB (1 to 100 micrograms/ml) at 37 degrees C for various time intervals (5, 10, 20, 30, 45, and 60 min). After each interval, serum was removed and separated into high-density lipoprotein (HDL) and low-density lipoprotein (LDL) fractions by an LDL-direct assay. The distribution of AmB (Fungizone) at 5 min through 1 h of incubation at 25 degrees C remained constant and was similar in the HDL and LDL fractions. At 37 degrees C, at 5 through 45 min of incubation, 54 to 61% of AmB was recovered in the HDL fraction; however, at 1 h more than 75% of the AmB concentration was recovered in the HDL fraction. In contrast, 87.5 to 92% AmB was recovered in the HDL fraction throughout the incubation when negatively charged liposomal AmB (dimyristoylphosphatidylcholine [DMPC]:dimyristoylphosphatidylglycerol [DMPG], 7:3 [wt/wt]) was used. With positively charged liposomes, 75 to 87.7% of AmB was recovered in the HDL fraction through the different time points studied. AmB incorporated into DMPC (neutral) and DMPG (negative) liposomes, and AmB was distributed in an HDL:LDL ratio of 6:4 following 1 h of incubation. Ninety percent of AmB and 80% of the lipid were found in the HDL fraction in a 3:1 molar DMPG:AmB ratio and in the LDL fraction in a 6:1 molar ratio. Lipid charge and temperature play a role in AmB distribution into serum lipoproteins. AmB and DMPG may contransfer as an intact drug-lipid complex to serum lipoproteins.

Amphotericin B↗
PubMed1992

Serum and organ indices of the mdx dystrophic mouse.

Duchenne muscular dystrophy (DMD) is a fatal disease for which there is no effective treatment. The cause of death in patients with DMD is often cardiovascular and pulmonary dysfunction. This clinical observation, combined with experimental findings, suggests that other non-muscle organ systems may be affected in the dystrophic disease state. To test this hypothesis, the present study investigated liver and kidney function in the mdx mouse. Serum chemistries and the hepatic cytochrome P-450 system in normal and dystrophic mdx mice were investigated at two different ages. Increases in serum lactate dehydrogenase (LDH), alkaline phosphatase (AP), aspartate transaminase (AST), and cholesterol levels, combined with an increase in liver weight and a decrease in cytochrome P-450, suggests the possibility of hepatic dysfunction. Increases in serum uric acid and phosphorus, and decreased kidney weight suggest hepatic dysfunction.

Animals↗
PubMed1990

Mechanisms of creatine kinase release from isolated rat skeletal muscles damaged by propylene glycol and ethanol.

The organic cosolvents propylene glycol and ethanol are found to cause skeletal muscle damage and creatine kinase release following intramuscular injection. The mechanisms of this organic cosolvent-induced enzyme release have not been elucidated. Cosolvent-induced creatine kinase release was enhanced by the addition of calcium to the incubation medium, and inhibited, albeit modestly, by dibucaine, a nonspecific phospholipase A2 inhibitor. The temporal pattern of creatine kinase release further suggested that cosolvent-induced enzyme release from skeletal muscles may be caused by an intracellular mechanism rather than by a direct solubilization of sarcolemma. This intracellular mechanism may involve the mobilization of calcium.

Animals↗
PubMed1990

Effect of organic cosolvent-induced skeletal muscle damage on the bioavailability of intramuscular [14C]diazepam.

Organic cosolvents are used in many intramuscular formulations for solubilization of drugs and have been shown to cause skeletal muscle damage (myotoxicity). This study explored the influence of organic cosolvent-induced myotoxicity on the bioavailability of a model compound, diazepam. A tracer (C14) dose of diazepam was selected which did not elicit any systemic pharmacologic effects (viz., hypothermia and sedation) that might alter the pharmacokinetics of the drug. Male New Zealand White rabbits were injected with diazepam dissolved in three cosolvent: water mixtures (20% v/v propylene glycol, 20% v/v polyethylene glycol 400, and 50% v/v polyethylene glycol 400). These mixtures have similar physicochemical properties, but vary 10-fold in their in vitro myotoxicity. Using plasma total radioactivity following intramuscular administration of diazepam, statistical differences were not detected in the area under the curve (AUC), the peak concentration, and the time of the observed peak concentration among these treatments, although the in vivo myotoxicity of these systems (measured by the plasma creatine kinase AUC) varied by 10-fold (p less than 0.01). Limited data on unchanged diazepam levels confirmed these observations. Thus, the degree of skeletal muscle damage caused by these organic cosolvent systems does not seem to affect the bioavailability of a tracer dose of intramuscular diazepam.

Animals↗