Vasoactive properties of lignocaine administered by iontophoresis in human skin

The vasoactivity of lignocaine has an important influence on its clinical efficacy and systemic vascular absorption. The aim of this study was to evaluate its vasoactive properties when administered by the non-invasive technique of iontophoresis. We used laser Doppler imaging to measure the forearm skin blood flow responses of seven healthy young males to iontophoretic delivery of two preparations of 20 g/l of lignocaine hydrochloride, one containing the preservatives methylparaben and propylparaben and one without. The subjects were blind to the order of drug administration, and we assessed analgesia at the sites using a pinprick test. Delivery of both preparations of (positively charged) lignocaine under the anode caused demonstrable analgesia, but no change in skin blood flow. An increase in perfusion was measured, however, when the preservative-containing preparation was administered under the cathode. There was little or no response to the solution without preservatives, although the difference in response between the two preparations was not statistically significant (P =0.063). Although there were no vasoactive effects of lignocaine at the relatively low dose used in the present study, our results suggest that the preservatives methylparaben and propylparaben are the most likely cause of the vasodilatation that we observed under the cathode, and may therefore have a significant influence on the vasoactivity of this preparation when administered by injection. Both are negatively charged in solution and have been reported to possess vasodilator properties. It might be worth considering the use of alternative, non-vasoactive preservatives in local anaesthetic preparations, or avoiding the use of additives altogether, when this is feasible.

A new platelet preservative

A new platelet preservative, ViaCyte trade mark (balanced salt solution, physiological buffer, D-ribose, bovine serum albumin, D-glucose, sterile water) was tested against the presently used storage solution (citrate-phosphate-dextrose; CPD) and results revealed that ViaCyte demonstrated added protection for platelets during storage-induced activation. Following five days of storage at room temperature, only 12.2% of platelets stored in ViaCyte exhibited P-selectin expression at rest and, upon thrombin challenge, 64.2% were activated, an increase of 42%. In control platelets (platelets stored in CDP), 44.4% were activated due to storage-induced lesions, and thrombin stimulation resulted in 47.9% P-selectin expression, an increase of only 2.5%. ViaCyte storage maintained the resting state and preserved platelet function, making more platelets available for activation upon agonist challenge. This preliminary study demonstrated that the presently used standard preservative does not offer protection from storage-induced lesions. Partially dysfunctional platelets do not contribute significantly to hemostasis in vivo and play little role, if any, in clot retraction and wound healing processes.

Development of the antimicrobial effectiveness test as USP chapter <51>

The antimicrobial effectiveness test first appeared as a USP General Chapter in the 18th revision, official September 1, 1970. This chapter, at the beginning, was designed to evaluate the performance of antimicrobials added to inhibit the growth of microorganisms that might be introduced during or subsequent to the manufacturing process. As Good Manufacturing Practices (GMPs) became a governing principal in pharmaceutical manufacturing, the purpose of the test was refined to focus on activity of the preservative system as a protection against inadvertent contamination during storage and usage of the product. This article will review the history of the antimicrobial test; its function, technique, and the background discussions that resulted in the changes from the test that appeared in USP XVIII to that of the current USP 25.

Cytoprotective effects of hyaluronic acid and Carbomer 934P in ocular surface epithelial cells

PURPOSE

To investigate in vitro the cell toxicity and antioxidant effects of two major tear substitutes, hyaluronic acid and a widely used carbomer, with and without preservative.

METHODS

Chang conjunctival cells were treated with different concentrations of unpreserved or preserved carbomer 934P (0.03% and 0.3%), unpreserved or preserved hyaluronic acid (0.018% and 0.18%), and benzalkonium chloride (BAC 0.0005% and 0.005%) for 15 minutes or for 15 minutes with 24 hours of cell recovery, according to previously validated methods. Microplate cold light cytofluorometry was performed to evaluate cell viability (neutral red test), chromatin condensation (Hoechst 33342 test), and reactive oxygen species (ROS) production (dichlorofluorescein diacetate and hydroethidine tests). Confocal microscopy was used to explore morphologic changes.

RESULTS

No alterations were found with unpreserved and preserved hyaluronic acid at all concentrations and times tested. A decrease in cell viability with chromatin condensation appeared with 0.3% preserved carbomer 934P at the two times tested. This cytotoxicity, however, was significantly less than that observed with BAC alone, although the same concentrations of preservative were used. Unpreserved carbomer 934P induced no modification of cell viability after 15 minutes but a significant decrease in chromatin condensation, reversible after 24 hours of cell recovery, when a delayed decrease in cell viability was observed. Production of reactive oxygen species (ROS) decreased with the four formulations of tear substitutes tested at their usual concentrations, whereas a significant production of ROS occurred with BAC.

CONCLUSIONS

These two ophthalmic hydrogels have no cytotoxicity but possess antioxidant properties and tend to reduce the toxic effects of preservatives. These results may allow use of hydrogels, not only in dry eye but also in ocular surface disorders involving oxidative stress and in ophthalmic drug therapy to improve ocular tolerance.

[Human trabecular cells and apoptosis: in vitro evaluation of the effect of betaxolol with or without preservative]

PURPOSE

Trabecular meshwork, which is involved in aqueous outflow resistance, is deeply modified in glaucoma patients, with a decrease in the trabecular cell number. Trabecular toxicity of antiglaucoma medications cannot be excluded. On a human cultured trabecular cell line, we investigated the potential proapoptotic effect of a beta-blocker with or without preservative, benzalkonium chloride (0.01% BAC), by flow cytometry and confocal microscopy.

MATERIAL

and

METHODS

A human immortalized trabecular cell line (HTM-5) obtained from a normal donor was cultured under normal conditions. Preserved 0.25% betaxolol suspension (betaxolol BAC +), unpreserved 0.25% betaxolol suspension, and 0.01% BAC were respectively added to the culture medium in a 1/10 or 1/100 dilution for 15 minutes. After a 24-hour recovery period in normal culture conditions, cell size and the expression of an apoptotic marker, Apo 2.7, were evaluated by flow cytometry and confocal microscopy. Untreated trabecular cells were used as control cells.

RESULTS

Preserved and unpreserved betaxolol in a 1/10 dilution induced a significant decrease in trabecular cell size compared to controls. However, this cell size decrease was less pronounced than that induced by BAC at the same dilution. Similar results were obtained with betaxolol and BAC in a 1/100 dilution. Trabecular cell Apo 2.7 expression was significantly increased after treatment with betaxolol BAC + and BAC- in a 1/10 dilution compared to controls (36.8%, 28.1%, and 15.4%, respectively p<0.005). However, this proapoptotic activity was much less pronounced than that induced by BAC- at the same dilution (96.9%, p<10(-4)). Unpreserved betaxolol in a 1/100 dilution had no apoptotic activity on trabecular cells. Trabecular cell Apo 2.7 expression slightly increased with betaxolol BAC + at a 1/100 dilution (24.9%, p=0.04), while it was greatly increased with BAC at the same dilution (39.9%; p<10(-4)).

CONCLUSION

In our model, unpreserved betaxolol at a low concentration displayed no proapoptotic activity on trabecular cells. On the other hand, preserved betaxolol displayed a moderate proapoptotic activity by triggering cell death of around 25% of cells. Trabecular cell toxicity appeared to be mainly due to the preservative benzalkonium chloride (BAC). Taken together, our results demonstrated that the strong apoptotic activity of BAC was greatly reduced within the preserved eye drops, probably through the interaction of BAC with the active compound.

prbA, a gene coding for an esterase hydrolyzing parabens in enterobacter cloacae and Enterobacter gergoviae strains

The new gene prbA encodes an esterase responsible for the hydrolysis of the ester bond of parabens in Enterobacter cloacae strain EM. This gene is located on the chromosome of strain EM and was cloned by several PCR approaches. The prbA gene codes for an immature protein of 533 amino acids, the first 31 of which represent a proposed signal peptide yielding a mature protein of a putative molecular mass of 54.6 kDa. This enzyme presents analogies with other type B carboxylesterases, mainly of eukaryotic origin. The cloning and expression of the prbA gene in a strain of Escherichia coli previously unable to hydrolyze parabens resulted in the acquisition of a hydrolytic capacity comparable to the original activity of strain EM, along with an increased resistance of the transformed strain to methyl paraben. The presence of homologues of prbA was tested in additional ubiquitous bacteria, which may be causative factors in opportunistic infections, including Enterobacter gergoviae, Enterobacter aerogenes, Pseudomonas agglomerans, E. coli, Pseudomonas aeruginosa, and Burkholderia cepacia. Among the 41 total strains tested, 2 strains of E. gergoviae and 1 strain of Burkholderia cepacia were able to degrade almost completely 800 mg of methyl paraben liter(-1). Two strains of E. gergoviae, named G1 and G12, contained a gene that showed high homology to the prbA gene of E. cloacae and demonstrated comparable paraben esterase activities. The significant geographical distance between the locations of the isolated E. cloacae and E. gergoviae strains suggests the possibility of an efficient transfer mechanism of the prbA gene, conferring additional resistance to parabens in ubiquitous bacteria that represent a common source of opportunistic infections.

The effect of benzalkonium chloride on rabbit nasal mucosa in vivo: an electron microscopy study

In this study we investigated the histopathological changes of nasal mucosa after the use of topical benzalkonium-chloride solution. In the study, 28 male New Zealand white rabbits were used. The animals were divided into two groups. In the first group, 50 micro l of 0.001% benzalkonium-chloride solution was sprayed into the right nostril and 50 micro l of 0.9% saline into the left twice daily for 14 days. In the second group, the same solutions were applied twice daily for 28 days. All of the biopsies from each nasal cavity were processed for electron microscopy. In the nostrils treated with 0.001% benzalkonium chloride, there were areas with obvious squamous cell metaplasia. Some cells showed broken cristae of the mitochondria. Degenerative changes in the supportive and olfactory cells, deformation of nuclei and the increase of heterochromatin were observed. The present investigation has shown that the application of topical benzalkonium chloride does induce degenerative morphologic changes in the nasal mucosa in rabbits in vivo.

Non-preserved 1% lidocaine solution has less antibacterial properties than currently available anaesthetic eye-drops

PURPOSE

Some anaesthetics inhibit bacterial growth, and thus may lead to low rates of positive cultures from bacterial keratitis. Antibacterial properties of lidocaine were compared with those of oxybuprocaine or tetracaine, either in current commercial eye lotions or in extemporaneous solutions.

METHODS

Forty-eight bacterial strains were used to determine the minimum inhibitory and bactericidal concentrations of four commercial eye lotions containing oxybuprocaine or tetracaine, of a non-ophthalmic 1% lidocaine commercial solution and of extemporaneously prepared solutions of oxybuprocaine, tetracaine, lidocaine and benzalkonium.

RESULTS

Most strains had their growth inhibited by 0.2% oxybuprocaine or 0.4% tetracaine, which corresponds to a 1/2 dilution of the commercial eye-drops. Bacterial growth was still observed with a 1% lidocaine solution.

CONCLUSIONS

Currently available anaesthetic eye-drops that are used before corneal specimen collection may lead to false-negative bacterial cultures. Conversely, a non-preserved 1% lidocaine solution might be more appropriate in corneal specimen collection.

Microbiological quality of topical drug formulations: efficacy of antimicrobial preservation against Paecilomyces lilacinus

BACKGROUND

Microbiological quality of topical products comprises both, the microbiological purity of the unopened product and the efficacy of the antimicrobial preservation system.

OBJECTIVE

Subsequent to an outbreak of invasive Paecilomyces lilacinus mycosis among patients of an isolation ward, probably caused by a contaminated skin care product, the microbiological quality of different skin care products from the market was investigated.

METHODS

The different products were investigated for their efficacy of antimicrobial preservation in general and especially against P. lilacinus according to a pharmacopoeial routine method slightly adopted for the purpose of this investigation.

RESULTS

The products did partially not comply with the British Pharmacopoeia 1993 test for efficacy of antimicrobial preservation. The antimicrobial preservation systems were less effective against P. lilacinus than against the pharmacopoeial reference germs. The antimicrobial preservation efficacy decreased towards the end of the shelf-life of the product. A decreased P. lilacinus inoculum dose was related to an increased growth of the micro-organisms.

CONCLUSION

Topical products are, unless not labelled otherwise, non-sterile preparations and their preservation systems are only tested against pharmacopoeial key micro-organisms. The microbiological behaviour following contamination with other germs remains unknown.

Bronchial reactions to the inhalation of high-dose tobramycin in cystic fibrosis

It has been established that inhaled tobramycin has a positive effect on respiratory function in Pseudomonas-aeruginosa positive patients with cystic fibrosis (CF). In a previous study the authors reported that low-dose tobramycin preparations containing the preservative phenol caused significant bronchial obstruction. Recently, high-dose tobramycin preparations with and without preservatives/phenol have become available. To assess the airway response to these preparations flow/volume curves in 12 patients with CF (four males, eight females, mean age+/-SD=19.0+/-7.4 yrs) were measured. The tobramycin preparations: Nebicina 2.0 mL (150 mg, containing the preservative phenol), Distobram 3.0 mL (150 mg, containing preservatives), Tobi 5.0 mL (300 mg), Tobi 2.5 mL (150 mg), and Tobi 5.0 mL, were used after bronchodilator application. Immediately and/or 5 min after the tobramycin inhalations there was a significant fall in lung function with the different preparations. There was no significant difference between preparations with and without preservatives/phenol. The bronchial obstruction was comparable to that observed after the inhalation of low-dose tobramycin and after saline. After 10 min of inhalation, the lung function returned to baseline values. Most patients preferred the Tobi 2.5 mL and disliked the Nebicina preparation due to the unpleasant taste. Preceding treatment with bronchodilators prevented the decline in lung function. Assessment of bronchial response at the first nebulisation of high-dose tobramycin and, in case of significant obstruction, beta-agonists in combination with the antibiotic inhalation are recommended.

Physicochemical screening of antimicrobial agents as potential preservatives for submicron emulsions

Antimicrobial agents should be added to lecithin-stabilized submicron emulsions when these preparations are non-sterile products or when packed in multidose containers. Eleven antimicrobials were introduced to a standard submicron emulsion. The emulsions were adjusted to pH 5.0 or 8.2 prior aseptic filtration or thermal sterilization, respectively. The physicochemical stability of the preparations was observed during storage for 2 years at room temperature. Parabens showed the best compatibility but satisfying stability was also observed in emulsions containing phenylethanol, m-cresol and benzalkonium chloride. Partitioning studies revealed poor correlation between aqueous solubility and content of the preservatives in the aqueous phase of the emulsion. Only 1.2% of the total content of benzalkonium chloride was found in this phase and incorporation of this compound into different microscopic structures of the emulsion is proposed as a reason for such effect. Preliminary studies on the efficacy of antimicrobial preservation was performed for emulsions containing parabens, benzalkonium chloride or chlorocresol and the negative results bring conclusion that higher concentration of antimicrobials or their combination may be required for efficient preservation of submicron emulsions.

Effects of anti-inflammatory drugs and preservatives on morphologic characteristics and migration of canine corneal epithelial cells in tissue culture

OBJECTIVE

To determine the effects of commonly used ophthalmic corticosteroids, suprofen, polysulfated glycosaminoglycan and preservatives on morphologic characteristics and migration of canine corneal epithelium grown in cell culture.

ANIMALS STUDIED

Corneal epithelial cells harvested from the corneas of euthanized dogs were propagated in cell culture.

PROCEDURES

Canine corneal epithelium was grown in tissue culture. The cells were treated with different corticosteroids, polysulfated glycosaminoglycan, suprofen or preservatives at different concentrations after a defect was created in the monolayer. Cellular morphologic characteristics and closure of the defect were compared between test drugs and controls.

RESULTS

Morphologically the cells treated with dexamethasone were essentially the same as controls. Prednisolone and hydrocortisone caused rounding and shrinkage of the cells. Both suprofen and polysulfated glycosaminoglycan caused no apparent changes in morphologic characteristics at the lowest concentrations tested, but at higher concentrations there was a concentration-dependent degree of rounding and shrinkage. Benzylkonium chloride and thimerosal caused rounding and shrinkage of all the cells at all concentrations tested. Dexamethasone, hydrocortisone, and suprofen did not inhibit epithelial migration over the defects at the lowest concentrations tested. All other drugs and concentrations inhibited cellular migration.

CONCLUSION

Dexamethasone affected the morphologic characteristics and migration of corneal epithelial cells less than hydrocortisone and prednisolone; therefore, dexamethasone may be the drug of choice when a corticosteroid is indicated and an epithelial defect is present. Suprofen and polysulfated glycosaminoglycan caused a concentration-dependent effect on morphologic characteristics and migration. The preservatives caused severe changes and inhibited migration of the canine corneal epithelial cells at all concentrations and may therefore contribute to poor epithelialization of ulcers treated with preservative-containing drugs.

Effect of preservatives on IgG aggregation, complement-activating effect and hypotensive activity of horse polyvalent antivenom used in snakebite envenomation

Intravenous administration of antivenoms is associated with early adverse reactions in a number of cases, but the causes of this phenomenon are still unclear. The effect of preservatives (phenol and thimerosal) on IgG aggregate and dimer formation, in vitro complement-activating effect and hypotensive activity of a whole IgG horse liquid polyvalent antivenom, produced by caprylic acid fractionation, was assessed. These parameters were studied since they have been associated with the development of early adverse reactions to the administration of antivenoms and human immunoglobulins. After a three-year storage period at 4 degrees C, antivenoms with preservatives had an increased content of IgG aggregates and dimers when compared with antivenom devoid of phenol and thimerosal. These observations correlate with a slight increment in the turbidity of preservative-containing antivenoms. The three antivenoms studied (formulation: no preservatives; with phenol and thimerosal; with thimerosal alone) activated human complement in vitro, with only minor quantitative differences among them. When antivenoms were administered as a bolus intravenous injection in rats, a rapid and prominent hypotension of short duration was observed after injection of phenol-containing antivenom, whereas such an effect was absent in antivenom free of preservative and in the one containing only thimerosal. Bolus injection of saline solution with phenol resulted in a similar hypotension, indicating that the effect is due to phenol. However, when phenol-containing antivenom was diluted 1:5 with saline solution before infusion, as occurs in the clinical use of this product, no hypotension was observed. Our results stress the need to evaluate the effects of preservatives on the physicochemical and pharmacological characteristics of antivenoms.

Developmental expression of the calcium release channels during early neurogenesis of the mouse cerebral cortex

The developmental changes of intracellular calcium release channels of mouse neocortex were studied at the onset of neurogenesis, which occurs between embryonic days E11 and E17. The three main isoforms of the two families of intracellular calcium release channels, namely the inositol trisphosphate receptors (IP3R) and the ryanodine receptors (RyR), were detected by their transcripts in the cerebral hemispheres, as early as stage E11. The major isoforms of each family, IP3R-1 and RyR-2, were found at the protein level by Western blot analysis. Expression of these proteins increases progressively throughout brain development. Their localization in coronal sections of cortex has been observed by immunodetection from E12, and compared to the TuJ1 (anti-class III beta-tubulin antibody) neuronal specific labelling. The expression of both channels is greatly enhanced after E12, and both were seen to be present in most of the proliferative and neuronal cells of the slice. Between E12 and E13, there is a striking transition in the pattern of calcium release elicited by specific agonists of these channels, thimerosal for IP3R and caffeine for RyR. The signals induced by thimerosal were not zone-specific, while the observed calcium release signals induced by caffeine were predominantly restricted out of the ventricular zone. This zone-specific caffeine sensitivity is consistent with the main RyR localization immunodetected at E13. Our results indicate that there is a time lag of several days between the molecular detection of calcium release channels and their functional expression, around the time of neuronal differentiation. Altogether, they provide a molecular basis for analyzing the developmental modulation of calcium signals useful for neurogenesis progression.

[Absence of interaction between thiomersal and aluminum occlusion chambers]

BACKGROUND

Positive patch tests to thiomersal are frequent, but of little relevance. Interaction between aluminium occlusive chambers and the mercury of thiomersal may elicit skin irritation and cause false positive results.

METHODS

Between January 1998 and May 1999, the patients were simultaneously patch tested with aluminium and plastic chambers. Positive skin tests were compared.

RESULTS

Seventeen of 213 subjects showed positive tests: 15 with the 2 materials, 1 only for the aluminium chamber, 1 for the plastic chamber.

DISCUSSION

The results did not differ for the two materials. We concluded that positive reactions observed were not caused by interaction between aluminium and thiomersal.

Mitochondrial activity and glutathione injury in apoptosis induced by unpreserved and preserved beta-blockers on Chang conjunctival cells

PURPOSE

Quaternary ammonium ions have been demonstrated to induce apoptosis correlated with superoxide anion production in vitro. The purpose of this study was to further investigate the mechanisms of benzalkonium chloride (BAC), unpreserved and preserved beta-blocker eye-drops-induced programmed cell death, with special attention to the roles of mitochondrial transmembrane potential and intracellular reduced glutathione.

METHODS

Chang conjunctival cells were incubated with different concentrations of unpreserved or preserved timolol (0.1%, 0.25%, and 0.4%), or carteolol (1% and 2%), or BAC (0.0001% to 0.01%) for 15 minutes, or for 15 minutes with a 24-hour recovery period in normal medium. Cellular viability (neutral red test), mitochondrial activity (rhodamine 123 test), intracellular reduced glutathione (monochlorobimane test), DNA condensation (Hoechst 33342 test), and reactive oxygen species (ROS) production (dichlorofluorescein diacetate and hydroethidine tests) were evaluated using microplate cold-light cytofluorometry.

RESULTS

A significant, concentration-dependent decrease in cellular viability was found with preserved beta-blockers and with BAC alone, whereas unpreserved preparations did not show any toxicity. Only preserved beta-blockers induced chromatin condensation associated with an alteration of mitochondrial activity and a decrease of glutathione, suggesting an apoptotic phenomenon. BAC increased glutathione after 15 minutes, whereas a decrease was observed after a recovery period. ROS production was found with preserved formulations at significantly higher levels than those observed with unpreserved drugs.

CONCLUSIONS

This in vitro study demonstrates that oxidative stress, evidenced by enhanced ROS production and mitochondrial injury rather than by cellular glutathione depletion, is a mechanism involved in apoptosis induced by preservative-containing eye-drops.

A case study of preservation of semi-solid preparations using the European Pharmacopoeia test: comparative efficacy of antimicrobial agents in zinc gelatin

The present study was undertaken with the aim of finding an alternative preservative system to methyl parahydroxybenzoate in zinc gelatin, which was described in the monographs of the Swiss Pharmacopoeia (until Ph. Helv. 8) and in previous editions of the German Pharmacopoeia (until DAB 7). This antimicrobial agent has now been withdrawn in the DAB, because of its potential allergy risks. As for the USP and DAB-DDR zinc gelatin preparations, they have always been devoid of any preservative agent, probably relying on the mild antimicrobial activity of zinc. A literature survey did not reveal if such an aqueous preparation containing the water-insoluble zinc oxide shows efficacious antimicrobial activity by itself. Thus, a comparative evaluation of differently preserved zinc gelatin preparations was performed using a test for the efficacy of antimicrobial preservation that has been modified with regard to the European Pharmacopoeia (EP) test to take into account the solid state of the preparations and the bactericidal effect of the zinc. Three zinc gelatin preparations were checked, either: (i), without any agent; or (ii), with 0.1% methyl parahydroxybenzoate; or (iii), with 0.5% phenoxyethanol, a broad-spectrum antimicrobial agent almost devoid of allergy risks. The three preparations behave quite differently, in particular with respect to fungi. All three preparations passed the modified EP test as far as bacteria are concerned. Even zinc gelatin without preservative is very effective, not only because of the mild antimicrobial activity of zinc (the soluble fraction of zinc oxide in the liquid phase of zinc gelatin was determined to be 13 microg/ml), but most probably because of the low water activity of the preparation (measured as around 0.81), as shown by the absence of growth of a zinc-resistant strain of Pseudomonas aeruginosa. Zinc gelatin preserved with methyl parahydroxybenzoate has a weak, although satisfactory, activity against Staphylococcus aureus. Regarding fungi, gelatin without an antimicrobial agent and that preserved with methyl parahydroxybenzoate meet the requirements for efficacy against Candida albicans, but are only bacteriostatic against Aspergillus niger. As for zinc gelatin preserved with phenoxyethanol, it displays the best activity against C. albicans and, above all, appears to be the only formulation exhibiting fungicidal activity against A. niger. It is therefore recommended to preserve zinc gelatin with this antimicrobial agent, as recently adopted in Supplement 2000 of the Swiss Pharmacopoeia.

Hydrolysis of 4-hydroxybenzoic acid esters (parabens) and their aerobic transformation into phenol by the resistant Enterobacter cloacae strain EM

Enterobacter cloacae strain EM was isolated from a commercial dietary mineral supplement stabilized by a mixture of methylparaben and propylparaben. It harbored a high-molecular-weight plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens as found in the mineral supplement (1,700 and 180 mg of methyl and propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very high concentrations of methylparaben (3,000 mg liter(-1), or 19.7 mM). This strain was able to hydrolyze approximately 500 mg of methyl-, ethyl-, or propylparaben liter(-1) (3 mM) in less than 2 h in liquid culture, and the supernatant of a sonicated culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of methylparaben liter(-1) (6.6 mM) in 15 min. The first step of paraben degradation was the hydrolysis of the ester bond to produce 4-hydroxybenzoic acid, followed by a decarboxylation step to produce phenol under aerobic conditions. The transformation of 4-hydroxybenzoic acid into phenol was stoichiometric. The conversion of approximately 500 mg of parabens liter(-1) (3 mM) to phenol in liquid culture was completed within 5 h without significant hindrance to the growth of strain EM, while higher concentrations of parabens partially inhibited its growth.

Effects of propofol containing EDTA on mineral metabolism in medical ICU patients with pulmonary dysfunction

OBJECTIVE

To determine whether the addition of disodium edetate (EDTA) to propofol significantly alters mineral metabolism, adverse events, and outcome in critically ill medical patients with acute pulmonary dysfunction.

DESIGN

Multicentre, double-randomised, double-blind, comparative trial.

SETTING

Medical intensive care units of 5 health centres.

PATIENTS

A total of 85 haemodynamically stable men and women aged 18-81 years who had pulmonary dysfunction or adult respiratory distress syndrome as a primary diagnosis or complication and who were expected to require at least 48 hours of sedation and mechanical ventilation.

INTERVENTIONS

Patients were randomised to receive propofol with or without EDTA and then to 1 of 2 sedation levels: light (Modified Ramsay Sedation Scale [MRSS] score of 2 to 3) or deep (MRSS score of 4 to 5). Propofol was administered by continuous infusion at an initial rate of 5 microg/kg per min and titrated as needed.

MEASUREMENTS AND RESULTS

Approximately 63 % of patients had a high severity of illness as indicated by an Acute Physiology and Chronic Health Evaluation II score > or = 19. As expected, these patients had a higher mortality rate but did not require a higher dose of propofol or propofol with EDTA. Extensive evaluation of cation homeostasis showed that ionised calcium and magnesium concentrations remained remarkably stable during treatment. Total calcium concentration was low as a result of hypoalbuminemia. Parathyroid hormone (PTH) concentration was elevated in both study groups at baseline, on day 4, and at the end of sedation. There were no significant differences in electrolyte levels and no progression to renal dysfunction. There were also no significant differences in haemodynamic or adverse-event profiles. Treatment-related adverse events occurred in 5 patients in each group; 4 of these (in 3 patients receiving propofol and 1 patient receiving propofol with EDTA) were considered serious. Because a large percentage of patients experienced a change in sedation level, no analyses were performed using sedation level.

CONCLUSIONS

The addition of EDTA to propofol does not alter calcium and magnesium homeostasis in critically ill patients with acute pulmonary dysfunction. The reason for the elevation in PTH concentrations in such patients is not known.

Propofol-containing sedatives increase levels of parathyroid hormone

OBJECTIVE

To evaluate the effects of propofol and propofol containing disodium edetate (ethylenediaminetetraacetic acid [EDTA]) on the parathyroid-calcium axis in normal subjects.

DESIGN

Randomised, double-blind, age-stratified, crossover trial.

SETTING

Single centre.

PATIENTS

A total of 50 healthy subjects.

INTERVENTIONS

Each subject was randomised to receive propofol or propofol containing EDTA on day 1 and the alternate treatment between days 15 and 29, with a 2-week wash-out period in between. On the day of treatment, subjects received a bolus of trial medication (1 or 2 mg/kg) followed by a 60-minute observation period. At the end of 60 minutes, subjects received trial medication infused for 60 minutes at 1 of 4 randomised infusion rates (25, 50, 100, or 200 microg/kg per min). Subjects were monitored for an additional 60 minutes following the infusion.

MEASUREMENTS AND RESULTS

Blood pressure, heart rate, respiratory rate, oxygen saturation, blood ionised calcium concentration, serum total magnesium concentration, serum intact parathyroid hormone (PTH) level, and plasma EDTA level were assessed at periodic intervals during and following the bolus and continuous infusion of trial medication. Mean arterial pressure significantly decreased (p < 0.05) following the bolus injection of both trial medications and returned to baseline at 60 minutes; it significantly decreased again during the continuous infusion and returned to baseline during recovery. Heart rate and respiratory rate fluctuated in both groups with significant increases and decreases throughout the study period following the bolus injection; both returned to baseline during the recovery period in each group. Ionised calcium and total magnesium concentrations remained within normal limits and were unchanged in response to both study medications. PTH levels significantly increased following the bolus injection of both study drugs. The increase in PTH levels was greater with higher doses of study medication during the infusion period. There was no difference in the response of blood pressure, heart rate, respiratory rate, or PTH levels between propofol and propofol with EDTA. EDTA levels increased significantly during the infusion of propofol with EDTA, reaching mean levels of 240 ng/mL.

CONCLUSIONS

The results of this study indicate that propofol increases PTH levels in normal subjects; however, propofol with EDTA does not alter ionised calcium or total magnesium concentrations.

Trace element homeostasis during continuous sedation with propofol containing EDTA versus other sedatives in critically ill patients

OBJECTIVE

To evaluate changes in serum and urinary zinc, cobalt, copper, iron, and calcium concentrations in critically ill patients receiving propofol containing disodium edetate (disodium ethylenediaminetetraacetic acid [EDTA]) versus sedative agents without EDTA.

DESIGN

This was a randomised, open-label, parallel-group study with randomisation stratified by baseline Acute Physiology and Chronic Health Evaluation (APACHE II) scores.

SETTING

Intensive care units (ICU) in 23 medical centres.

PATIENTS

Medical, surgical, or trauma ICU patients 17 years of age or older who required mechanical ventilator support and sedation.

INTERVENTIONS

A total of 106 patients received propofol containing 0.005 % EDTA (propofol EDTA), and 104 received other sedative agents without EDTA (non-EDTA). Only the first 108 patients were assessed for urinary trace metal excretion. Twenty-four-hour urine samples were collected on days 2, 3, and 7 and every 7 days thereafter for determination of zinc, cobalt, copper, iron, and calcium excretion; EDTA levels; urine osmolality; albumin levels; and glucose levels. The first 143 patients were assessed for serum concentration of zinc, cobalt, copper, iron, and calcium; creatinine; blood urea nitrogen; and albumin at baseline and once during each 24-hour urine collection.

MEASUREMENTS AND RESULTS

For the assessment of trace metals, patients receiving propofol EDTA demonstrated increased mean urinary excretion of zinc, copper, and iron compared with the normal range. All patients receiving sedatives demonstrated increased urinary excretion of zinc and copper above normal reference values. Compared with the non-EDTA sedative group, the propofol EDTA group demonstrated increased urinary excretion of zinc and iron. Mean serum concentrations of zinc and total calcium were decreased in both patient groups. Serum zinc concentrations increased from baseline to day 3 in the non-EDTA sedative group but not in the propofol EDTA group. Renal function, measured by blood urea nitrogen, serum creatinine, and creatinine clearance, did not deteriorate during ICU sedation with either regimen.

CONCLUSION

This study showed that critical illness is associated with increased urinary losses of zinc, copper, and iron. Propofol EDTA-treated patients had greater urinary losses of zinc and iron and lower serum zinc concentrations compared with the non-EDTA sedative group. No adverse events indicative of trace metal deficiency were observed in either group. The clinical significance of trace metal losses during critical illness is unclear and requires further study.

Safety and efficacy of propofol with EDTA when used for sedation of surgical intensive care unit patients

OBJECTIVE

To compare propofol with disodium edetate (EDTA) and propofol without EDTAwhen used for the sedation of critically ill surgical intensive care unit (ICU) patients.

DESIGN

Prospective, randomised, multicentre trial.

PATIENTS

A total of 122 surgical ICU patients who required intubation and mechanical ventilation.

INTERVENTIONS

Patients were randomised to receive either propofol or propofol plus EDTA (propofol EDTA) by continuous infusion for sedation.

MEASUREMENTS AND RESULTS

The addition of EDTA to propofol had no effect on calcium or magnesium homeostasis, renal function, haemodynamic function, or efficacy when used for the sedation of surgical patients in the ICU. The most common adverse events were hypotension, atrial fibrillation, and hypocalcaemia. In this trial, a greater number of serious adverse events and adverse events leading to withdrawal occurred in the propofol group relative to the propofol EDTA group. There was a significantly lower crude mortality rate at 7 and 28 days for the propofol EDTA group compared with the propofol group. There were no statistically significant differences between groups with respect to depth of sedation.

CONCLUSION

The propofol EDTA formulation had no effect on calcium or magnesium homeostasis, renal function, or sedation efficacy compared with propofol alone when used for sedation in critically ill surgical ICU patients. There was a significant decrease in mortality in the propofol EDTA group compared with the propofol group. Further investigations are needed to validate this survival benefit and elucidate a possible mechanism.

Cation metabolism during propofol sedation with and without EDTA in patients with impaired renal function

OBJECTIVE

To compare the effects of propofol with and without disodium edetate (EDTA) on cation metabolism in intensive care unit (ICU) patients with renal insufficiency who received propofol or propofol plus EDTA (propofol EDTA) for sedation and mechanical ventilation.

DESIGN

Double-blind, randomised, multicentre study.

SETTING

Medical and surgical ICUs from 5 hospitals.

PATIENTS

Thirty-nine ICU patients with acute and chronic renal impairment expected to require at least 24 hours of continuous sedation and respiratory failure necessitating mechanical ventilation.

INTERVENTIONS

Propofol or propofol EDTA administered for sedation by continuous intravenous infusion.

MEASUREMENTS AND RESULTS

The depth of sedation, as measured by the Modified Ramsay Sedation Scale, was similar in the 2 groups, when adjusted for dosing differences. The amount of propofol required to maintain adequate sedation was decreased in both groups compared to propofol requirements in ICU patients with normal renal function. EDTA levels were elevated at baseline in both groups. In the propofol EDTA group, the EDTA levels increased further by 20 % but decreased to below baseline EDTA levels at 48 hours after sedation. In the propofol group, EDTA levels decreased during sedation and remained below baseline levels at 48 hours after sedation. PATIENTS in both groups were hypocalcaemic and hyperphosphataemic at baseline with low levels of 1,25-dihydroxyvitamin D and elevated parathyroid hormone (PTH) levels. Other than a slight difference in ionised serum calcium levels at 4 h after the start of sedation, there were no significant differences observed in serum calcium levels between the two groups. There were no significant differences in 1,25-dihydroxyvitamin D or PTH levels over time between the two groups. There was no significant effect on renal function in either group.

CONCLUSIONS

The results of this study suggest that adding EDTA to propofol does not adversely affect cation homeostasis or renal function when used for sedation of ICU patients with renal insufficiency. Although EDTA levels increased over time from baseline levels in patients with renal insufficiency who receive propofol EDTA, this increase does not appear to be clinically significant, and EDTA levels return to below baseline levels within 48 hours of discontinuing the propofol EDTA infusion. The efficacy of propofol with and without EDTA also appears comparable in these patients.