Ampicillin/sulbactam in elderly patients with community-acquired pneumonia.

PURPOSE: Age-related physiological changes affect body systems, altering pharmacokinetics, which may potentiate or alter the effects of drugs. The aim of this study was to assess the influence of age on the steady-state pharmacokinetics and pharmacokinetic/pharmacodynamic parameters of ampicillin/sulbactam in the population of elderly patients (age ≥65 years) with community-acquired pneumonia (CAP). PATIENTS AND METHODS: The pharmacokinetics and pharmacokinetic/pharmacodynamic parameters of ampicillin/sulbactam were determined at steady state in a total of 13 elderly patients with CAP following the administration of multiple intravenous doses of 2 g ampicillin + 1 g sulbactam (Unacid(®), Pfizer), each over 15 min thrice a day. RESULTS: A reduced C max, AUC0-8 h and total clearance, a prolonged half-life, and an increased steady-state volume of distribution were observed for ampicillin. The mean estimated free C min of 1.8 mg/L for ampicillin was higher than that predicted to be effective against Streptococcus pneumoniae. Based on an MIC90 of 1 mg/L for Streptococcus pneumoniae, the calculated T > MIC and T > 4 × MIC for ampicillin was 75-100 % (median 100 %) and 12.5-100 % (median 50 %), respectively. A T > 4 × MIC of at least 50 % was achieved in 7 of 13 elderly patients with CAP. CONCLUSIONS: Age and, probably, pneumonia did affect the pharmacokinetics of ampicillin and sulbactam. Despite the reduced C max, adequate free C min/MIC90 ratios due to impaired renal function were observed in elderly patients with CAP. In elderly patients without renal impairment and/or in severe infection with less susceptible pathogens, more frequent dosing of ampicillin 2 g/sulbactam 1 g can be necessary to avoid the risk of underdosing in CAP.

[Counterfeiting of eye drops?: a laboratory study of antibiotic eye drops purchased in two African countries]. / Counterfeiting von Augentropfen? : Eine Untersuchung von Antibiotikapräparaten aus 2 Ländern Afrikas.

INTRODUCTION: Counterfeit drugs are often ineffective and are considered a problem with an immense risk potential especially in the treatment of infectious diseases. Emerging and developing countries are particularly affected. Little is known about the extent of counterfeit antibiotic drugs used in eye care. In the present study we investigated antibiotic eye drops purchased in two African countries with respect to the active substance and its concentration in the sample. METHODS: A total of 33 antibiotic eye drops purchased in Kenya and the Democratic Republic of Congo were tested. The bottles were labeled to contain one of the following substances: the quinolones ciprofloxacin, levofloxacin and ofloxacin and the aminoglycosides gentamicin and tobramycin. Imported quality products as well as cheaper generic drugs were tested. Fluoroquinolones were determined by high pressure liquid chromatography (HPLC) and quantified by fluorescence measurement and aminoglycosides were tested by using a fluorescence polarization immunoassay. RESULTS: All samples were found to contain the declared drug. Nine samples (27%) showed an under-concentration by 10% or less and ten (30%) showed an increased concentration of 10% or more than indicated on the label. 75% of the original drugs but only 12% of the generic drugs had measured concentrations within the standard advisory ranges of ± 5% from the nominal value. CONCLUSION: Our results provide no evidence for significant criminal counterfeiting of eye drops in the studied countries. The frequent deviation from the stated concentration in the generic samples is cause for concern and justifies further investigation.

In vitro kinetics of delivery of tobramycin and ofloxacin from osmotic hydro gel expanders.

OBJECTIVE: High-hydrophilic osmotic self-inflating hydro gel expanders are well-accepted for implantation to achieve tissue expansion in defined parts of the body like skin, breast and orbital soft tissue. To prevent post-implantation infections effective antibiotic prophylaxis might be helpful. The suitability of this hydro gel consisting of a co-polymer of N-vinyl-pyrolidone and methyl-methacrylate as a drug delivery system for antibiotics was investigated in a laboratory setting simulating the orbit in a newborn. METHODS: In a first setting the dry expanders were incubated in a 0.3% solution (5 ml) of tobramycin and ofloxacin for 24 h (n = 10 for each substance, adsorbing 2.4 ml of the 0.3% solution, i.e. 7,200 µg antibiotic). Addressing the release of both antibiotics, the concentrations in 15 ml elution medium (0.9% sodium chloride, renewed after every sampling) were measured after 0.25, 1, 2, 6, 24, 48 and 72 h of elution. To simulate the clinical use in a second setting the expanders were dried after incubation in a 0.3% and 0.03% solution of tobramycin (n = 5 for each concentration) before measuring the release. RESULTS: The cumulative amount of tobramycin released after 72 h reached 7,157 µg, i.e. 99% of the initially loaded antibiotic. The cumulatively released amount of ofloxacin was 5,505 µg (76% of loading dose). Main fraction of release (about two thirds) was detected for both antibiotics for a elution period 0 - 24 h. In the periods 24 - 48 and 48 - 72 h the released amount of tobramycin was significantly higher than for ofloxacin. The release from expander dried after loading tobramycin was comparable: The cumulatively released amount of 0.3% and 0.03% incubation solution was 99% and 79% of loading dose, respectively. CONCLUSIONS: The investigated hydro gel expanders soaked in antibiotic solution can store and further on release sufficient amounts of tobramycin or ofloxacin to produce antimicrobial effective concentrations in vitro in the surrounding environment according to the breakpoints reported by EUCAST [14]. This principle, when used in a clinical setting, might help to eliminate post-implantation infection, which is one of the major complications in clinical use.

Characterization of nucleoside and DNA adducts formed by S-(1-acetoxymethyl)glutathione and implications for dihalomethane-glutathione conjugates.

S-(1-Acetoxymethyl)glutathione (GSCH(2)OAc) was synthesized and used as a model for the reaction of glutathione (GSH)-dihaloalkane conjugates with nucleosides and DNA. Previously, S-[1-(N(2)-deoxyguanosinyl)methyl]GSH had been identified as the major adduct formed in the reaction of GSCH(2)OAc with deoxyguanosine. GSCH(2)OAc was incubated with the three remaining deoxyribonucleosides to identify other possible adducts. Adducts to all three nucleosides were found using electrospray ionization mass spectrometry (ESI MS). The adduct of GSCH(2)OAc and deoxyadenosine was formed in yield of up to 0.05% and was identified as S-[1-(N(7)-deoxyadenosinyl)methyl]GSH. The pyrimidine deoxyribonucleoside adducts were formed more efficiently, resulting in yields of 1 and 2% for the GSCH(2)OAc adducts derived from thymidine and deoxycytidine, respectively, but their lability prevented their structural identification by (1)H NMR. On the basis of the available UV spectra, we propose the structures S-[1-(N(3)-thymidinyl)methyl]GSH and S-[1-(N(4)-deoxycytidinyl)methyl]GSH. Because adduct degradation occurred most rapidly at alkaline and neutral pH values, an enzymatic DNA digestion procedure was developed for the rapid hydrolysis of DNA to deoxyribonucleosides at acidic pH. DNA digests were completed in less than 2 h with a two-step method, which consisted of a 15 min incubation of DNA with high concentrations of deoxyribonuclease II and phosphodiesterase II at pH 4.5, followed by incubation of resulting nucleotides with acid phosphatase. Analysis of the hydrolysis products by HPLC-ESI-MS indicated the presence of the thymidine adduct.

Formation of indigo by recombinant mammalian cytochrome P450.

The development of bicistronic systems for coexpression of recombinant human cytochrome P450 enzymes (P450s) with their redox partner, NADPH-cytochrome P450 reductase (NPR), has enabled P450 activity to be reconstituted within bacterial cells. During expression of recombinant P450 2E1 and some other forms, we observed the formation of a blue pigment in bacterial cultures. The pigment was extracted from cultures and shown to comigrate with standard indigo on TLC. UV-visible spectroscopy and mass spectrometric analysis provided further support for identification of the pigment as indigo. Indigo is known to form following the spontaneous oxidation of 3-hydroxyindole. Accordingly, we speculated that indole, formed as a breakdown product of tryptophan in bacteria, was hydroxylated by the P450 system, leading to indigo formation. Bacterial membranes containing recombinant P450 2E1 and human NPR were incubated in vitro with indole and shown to catalyze formation of a blue pigment in a time- and cofactor-dependent manner. These studies suggest potential applications of mammalian P450 enzymes in industrial indigo production or in the development of novel colorimetric assays based on indole hydroxylation.

Formation and reactions of N(7)-aminoguanosine and derivatives.

Arylamines are mutagens and carcinogens and are thought to initiate tumors by forming adducts with DNA. The major adducts are C(8)-guanyl, and we have previously suggested a role for guanyl-N(7) intermediates in the formation process. N(7)-Aminoguanosine (Guo) was synthesized and characterized, with the position of the NH(2) at N7 established by two-dimensional rotating frame Overhauser enhancement NMR spectroscopy. In DMF, N(7)-NH(2)Guo formed C(8)-NH(2)Guo and the cyclic product C(8):5'-O-cycloGuo. In aqueous media, these products were formed along with 8-oxo-7,8-dihydroGuo, N(7)-NH(2)guanine, and a product characterized as a purine 8, 9-ring-opened derivative (N-aminoformamidopyrimidine). The rate of aqueous decomposition of N(7)-NH(2)Guo increased with pH, with a t(1/2) of 10 h at pH 7 and a t(1/2) of 2 h at pH 9. The rate of migration of NH(2) from N7 to C8 is fast enough to explain the formation of C(8)-NH(2)Guo from the reaction of 2, 4-dinitrophenoxyamine with Guo but not the formation of C(8)-(arylamino)Guo in the reaction of Guo with aryl hydroxylamine esters; however, the fluorenyl moiety may facilitate the proposed rearrangement by stabilizing an incipient negative charge in the transfer. In the reaction of Guo with N-hydroxy-2-aminofluorene and acetylsalicylic acid, a peak with the mass spectrum expected for N(7)-(2-aminofluorenyl)Guo was detected early in the reaction and was distinguished from C(8)-(2-aminofluorenyl)Guo. NMR experiments with [8-(13)C]Guo also provided some additional support for transient formation of N(7)-(2-aminofluorenyl)Guo. We conclude that a guanyl-N(7) intermediate is reasonable in the reaction of activated arylamines with nucleic acids, although an exact rate of transfer of an N(7)-arylamine group to the C8 position has not yet been quantified. The results provide an explanation for the numerous products associated with modification of DNA by activated arylamines. However, the contribution of "direct" reaction at the guanine C8 atom cannot be excluded.