Amoxycillin levels in sputum, serum, and saliva

Liquid Chromatography Mass Spectrometry Detection of Antibiotic Agents in Sputum from Persons with Cystic Fibrosis

Antibiotic therapy is expected to impact host microbial communities considerably, yet many studies focused on microbiome and health are often confounded by limited information about antibiotic exposure. Given that antibiotics have diverse pharmacokinetic and antimicrobial properties, investigating the type and concentration of these agents in specific host specimens would provide much needed insight into their impact on the microbes therein. Here, we developed liquid chromatography mass spectrometry (LC-MS) methods to detect 18 antibiotic agents in sputum from persons with cystic fibrosis. Antibiotic spike-in control samples were used to compare three liquid extraction methods on the Waters Acquity Quattro Premier XE. Extraction with dithiothreitol captured the most antibiotics and was used to detect antibiotics in sputum samples from 11 people with cystic fibrosis, with results being compared to the individuals' self-reported antibiotic use. For the sputum samples, two LC-MS assays were used; the Quattro Premier detected nanomolar or micromolar concentrations of 16 antibiotics, whereas the Xevo TQ-XS detected all 18 antibiotics, most at subnanomolar levels. In 45% of tested sputum samples (71/158), at least one antibiotic that was not reported by the subject was detected by both LC-MS methods, a discordance largely explained by the thrice weekly administration and long half-life of azithromycin. For ∼37% of samples, antibiotics reported as taken by the individual were not detected by either instrument. Our results provide an approach for detecting a variety of antibiotics at the site of infection, thereby providing a means to include antibiotic usage data into microbiome studies.

Development and validation of a sensitive LC-MS/MS method for the quantitation of IMB-YH-4py5-2H, an antituberculosis candidate, and its application to the pharmacokinetic study

(E)-N,N-dimethyl-4-oxo-4-(4-(pyridin-4-yl)phenyl)but-2-enamide hydrochloride (IMB-YH-4py5-2H) is a novel Protein Kinase B (PknB) inhibitor with potent activity against Mycobacterium tuberculosis strains. In the present study, a sensitive and specific liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine IMB-YH-4py5-2H in rat plasma. Sample pretreatment was achieved by liquid-liquid extraction with ethyl acetate, and separation was performed on an XTerra MS C₁₈ column (2.1×50 mm, 3.5 μm) with gradient elution (methanol and 0.1% formic acid) at a flow rate of 0.3 mL/min. Detection was performed in multiple reaction monitoring (MRM) mode. Linear calibration curves were obtained over a concentration range of 1−100 ng/mL. The intra-day and inter-day precisions were lower than 8.46%, and the accuracies ranged from -8.71% to 12.36% at all quality control levels. The extraction recoveries were approximately 70%, and the matrix effects were negligible. All quality control samples were stable under different storage conditions. The validated method was successfully applied to a preclinical pharmacokinetic study in Sprague-Dawley rats. IMB-YH-4py5-2H demonstrated improved pharmacokinetic properties (higher exposure level) compared with its leading compound. IMB-YH-4py5-2H was also distributed throughout the lung pronouncedly, especially inside alveolar macrophages, indicating its effectiveness against lower respiratory infections.

Concentrations of amoxicillin and clindamycin in teeth following a single dose of oral medication

OBJECTIVES

The main purpose of this study is the detection of amoxicillin and clindamycin concentrations in teeth.

MATERIALS AND METHODS

Eleven patients received 2 g of amoxicillin, and 11 patients received 600 mg of clindamycin in a single dose of oral medication at least 60 min prior to tooth extraction due to systemic diseases. The concentrations were determined in crowns and roots separately using liquid chromatography-tandem mass spectrometry (LC-MS-MS).

RESULTS

Amoxicillin (13 samples) and clindamycin (12 samples) were detected in the samples of the root and crown preparations of the extracted teeth. The mean concentration of amoxicillin was 0.502 μg/g in the roots and 0.171 μg/g in the crowns. The mean concentration of clindamycin was 0.270 μg/g in the roots and 0.064 μg/g in the crowns.

CONCLUSIONS

A single dose of oral amoxicillin and clindamycin leads to concentrations of both antibiotics in teeth which exceed the minimal inhibition concentration of some oral bacteria.

CLINICAL RELEVANCE

The proof of antibacterial activity in dental hard tissue after oral single-dose application is new. The antimicrobial effect of amoxicillin and clindamycin concentrations in roots of teeth may be of clinical relevance to bacterial reinfection from dentinal tubules.

Delivering Antibacterials to the Lungs

An important determinant of clinical outcome of a lower respiratory tract infection may be sterilization of the infected lung, which is also dependent on sustained antibacterial concentrations achieved in the lung. For this reason, recently there has been increased interest in measuring the concentration of antimicrobial agents at different potential sites of infection in the lung. Levels of antibacterials are now measured in bronchial mucosa, epithelial lining fluid (ELF) and alveolar macrophages, as well as in sputum. Penicillins and cephalosporins reach only marginal concentrations in bronchial secretions, whereas fluoroquinolones and macrolides have been shown to achieve high concentrations. The extent of penetration of different antibacterials into the bronchial mucosa is relatively high. This is also true for beta-lactams, although their tissue concentrations never reach blood concentrations. Antibacterials penetrate less into the ELF than into the bronchial mucosa, but fluoroquinolones appear to concentrate more into alveolar lavage than into bronchial mucosa. Pulmonary pharmacokinetics is a very useful tool for describing how drugs behave in the human lung, but it does not promote an understanding of the pharmacological effects of a drug. More important, instead, is the correlation between pulmonary disposition of the drug and its minimum inhibitory concentration (MIC) values for the infectious agent. The addition of bacteriological characteristics to in vivo pharmacokinetic studies has triggered a 'pharmacodynamic approach'. Pharmacodynamic parameters integrate the microbiological activity and pharmacokinetics of an anti-infective drug by focusing on its biological effects, particularly growth inhibition and killing of pathogens. Drugs that penetrate well and remain for long periods at the pulmonary site of infection often induce therapeutic responses greater than expected on the basis of in vitro data. However, although the determination of antibacterial concentrations at the site of infection in the lung has been suggested to be important in predicting the therapeutic efficacy of antimicrobial treatment during bacterial infections of the lower respiratory tract, some studies have demonstrated that pulmonary bacterial clearance is correlated more closely to concentrations in the serum than to those in the lung homogenates, probably because they better reflect antibacterial concentration in the interstitial fluid.

Does adjuvant antibiotic treatment after drainage of anorectal abscess prevent development of anal fistulas? A randomized, placebo-controlled, double-blind, multicenter study

BACKGROUND

The risk of fistula formation is a major concern after incision and drainage of an anorectal abscess.

OBJECTIVE

Our objective was to the test the effects of antibiotic treatment on fistula formation after incision and drainage of anorectal abscesses.

DESIGN

Randomized, placebo-controlled, double-blind study.

SETTING

Multicenter trial at 3 teaching hospitals in Turkey.

PATIENTS

Patients who underwent abscess drainage between September 2005 and January 2008 were evaluated for eligibility. Exclusion criteria included penicillin allergy, antimicrobial agent usage before enrolment, other infection, previous anorectal surgery, inflammatory bowel disease, suspicion of Fournier gangrene, secondary and recurrent anorectal abscesses, anal fistula at time of the surgery, immune compromised states, and pregnancy.

INTERVENTION

Patients were randomly assigned to receive placebo or amoxicillin-clavulanic acid combination treatment for 10 days after abscess drainage.

MAIN OUTCOME MEASURES

The primary end point was rate of anorectal fistula formation at 1-year follow-up.

RESULTS

: Of 334 patients assessed for eligibility, 183 entered the study (placebo, 92; antibiotics, 91). Data were available for per-protocol analysis from 151 patients (placebo, 76; antibiotics, 75) with a mean age of 37.6 years; 118 patients (78.1%) were men. Overall, 45 patients (29.8%) developed anal fistulas during 1-year follow-up. Fistula formation occurred in 17 patients (22.4%) in the placebo group and in 28 patients (37.3%) in the antibiotic group (P = .044). Risk of fistula formation was increased in patients with ischiorectal abscess (odds ratio, 7.82) or intersphincteric abscess (odds ratio, 3.35) compared with perianal abscess.

CONCLUSION

Antibiotic treatment following the drainage of an anorectal abscess has no protective effect regarding risk of fistula formation.

Antibiotic use in Cystic Fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the β-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Prevention of Surgical Site Infection After Open Prosthetic Inguinal Hernia Repair: Efficacy of Parenteral Versus Oral Prophylaxis with Amoxicillin-Clavulanic Acid in a Randomized Clinical Trial

The aim of this prospective study was to compare the efficacy of oral versus parenteral prophylactic amoxicillin-clavulanic acid for preventing surgical site infection after open prosthetic mesh repair of inguinal hernia. A total of 480 inguinal-hernia patients were randomly assigned to two groups. Group I (n = 240) received 1.313 g oral amoxicillin-clavulanic acid 2 hours before operation, and group II (n = 240) received 1.2 g of the same drug combination intravenously approximately 30 minutes before surgery. Patients were examined four times during 1 year of follow-up (at 7-10 days, 4-6 weeks, 6 months, and 12 months postoperation), and data related to surgical site infections were collected. Seventy-two patients were excluded due to confounding factors during and after the operation. There were no statistically significant differences between group I (final n = 208) and group II (final n = 200) with respect to age, sex distribution, body mass index, American Anesthesiology Association grade, frequencies of different hernia types, duration of surgery, and the experience levels of the principal surgeon in the operations. One of the 208 (0.5%) patients in group I and 3 of the 200 (1.5%) patients in group II developed superficial surgical site infections (p > 0.05). None of the infections required mesh removal. There were no deep surgical site infections in either group, and there was one case of hernia recurrence in each group. For patients undergoing open prosthetic repair of inguinal hernia, oral amoxicillin-clavulanic acid is safe, significantly less costly, and equally effective in preventing surgical site infection as the same dose given parenterally.

Penetration of amoxycillin into the respiratory tract tissues and secretions in pigs

The pharmacokinetic properties of amoxycillin, and its penetration into respiratory tract tissues (alveolar macrophages, bronchial secretions, bronchial mucosa, lung tissue and lymph nodes), were determined in 20 healthy female pigs weighing 29 to 55 kg, after a single intravenous dose of 8.6 mg kg(-1) bodyweight. Following intravenous administration the plasma concentration-time curves were best described by a three-compartment open model. The elimination half-life and the mean residence time were 2.5 and 1.4 hours, respectively. The volume of distribution at steady state was 0.52 litres kg(-1), and the body clearance was 0.40 litres hour(-1) kg(-1). In all structures (except alveolar macrophages) amoxycillin concentration peaked at the first sampling point, one hour after drug administration. The tissue to plasma ratio (based on AUC values) were 0.33 for bronchial secretions, 0.37 for bronchial mucosa, 0.39 for lung tissue and 0.68 for lymph nodes. Traces of amoxycillin were found in alveolar macrophages, but the concentrations were below the limit of quantification. The concentration of amoxycillin in secretions and tissue decreased by a slower rate than the concentration in plasma, resulting in increasing secretion- and tissue-to-plasma concentration ratios.

Pharmacokinetics of antimicrobial agents in the respiratory tract

The ability of antibiotics to penetrate into the respiratory tract has been investigated at several sites, namely, sputum and bronchial secretions, tissue homogenates, pleural fluid and, more recently, epithelial lining fluid and alveolar macrophages. The major reason for such investigations is that these data may be helpful to a more thorough understanding of drug distribution in the lung tissue and fluids and to a more accurate prediction of clinical outcome. However, the study of drug concentration at each of these sites presents problems in terms of methodology and data interpretation. The advantages and disadvantages of each of these methods are considered, and the data on penetration of betalactams, aminoglycosides, macrolides, fluoroquinolones and other antimicrobial agents (including antifungal and antiprotozoan drugs) are reviewed.

Concentration of meropenem in serum and in bronchial secretions in patients undergoing fibreoptic bronchoscopy

The objective of the study was to evaluate the ability of meropenem to reach the bronchial lumen. 24 patients undergoing fibreoptic bronchoscopy for exploratory purposes were given a single dose of meropenem 1 g as an (i.v., infusion over 30 min. Plasma (P) sampling times were: 0, 0.5, 1, 2 and 3 h. Bronchial secretions (BS) were collected by fibreoptic bronchoscopy at the same sampling times (except for 0 and 0.5 h) in three groups of 8 patients. Meropenem was measured by bioassay using E. coli ATCC 39118 as the test-organism. The results showed that meropenem had reached a high plasma concentration at the first sampling time (59.8 mg.l-1) and then the plasma level decreased rapidly to 10.6 mg.l-1 and 2.7 mg.l-1 at 2 and 3 h respectively. The highest concentration achieved in bronchial secretion was 0.53 mg.l-1 in the third hour, ie 20% of the serum level. The data indicate significant penetration of meropenem into bronchial secretions and achievement of a local level sufficiently high to eradicate most respiratory pathogens.

Use of an enzyme-linked immunosorbent assay to assess penetration of amoxicillin into lung secretions

An enzyme-linked immunosorbent assay (ELISA) was developed to measure total amoxicillin concentrations penetrating lung secretions, which were compared with "active" concentrations measured by conventional bioassay. An antibody was raised in rabbits to amoxicillin conjugated to bovine serum albumin and used in a competitive binding ELISA (sensitivity, 10 ng/ml; precision [coefficient of variation], 9%). The measurement of amoxicillin in lung secretions by using the ELISA method was verified by high-performance liquid chromatography. Amoxicillin concentrations were found to be similar in both whole sonicated sputum and sol-phase sputum obtained by ultracentrifugation following single oral doses of 3 g (4.6 mg/liter for sonicated and 4.7 mg/liter for sol-phase preparations) and 250 mg (0.23 mg/liter for both preparations). Eight patients with bronchiectasis received 500 mg of amoxicillin three times daily. On the second day of therapy (4 h after the morning dose), the mean concentration of amoxicillin in sputum was 0.88 mg/liter (standard error of the mean [SEM], 0.11) by ELISA and 0.40 mg/liter (SEM, 0.05) by bioassay, suggesting a significant degree of local inactivation. This difference between total and active amoxicillin levels was found to correlate significantly (r = 0.693; P less than 0.05) with beta-lactamase levels (mean, 29.5 mU/ml; SEM, 9.4). A pharmacokinetic study on day 3 revealed maximum levels in secretions 2 to 4 h after dosing (mean, 1.36 mg/liter; SEM, 0.26). At the end of successful therapy (day 14), total and active levels were lower (mean, 0.48 mg/liter; SEM, 0.11 [total]; mean, 0.21 mg/liter; SEM, 0.06 [active]); this result was associated with a reduction in lung inflammation (decreased serum-derived albumin in the lung secretions). In conclusion, antibiotic penetration is partly dependent on the degree of lung inflammation. The differences observed in total and active levels of amoxicillin and the relationship to beta-lactamase activity in sputum suggest why higher doses of antibiotic may be required to produce a therapeutic response in some patients.

Pulmonary disposition of antimicrobial agents: methodological considerations

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Penetration of lomefloxacin into bronchial secretions following single and multiple oral administration

The bronchial penetration of lomefloxacin, a new difluorinated quinolone, was evaluated in 36 patients who underwent bronchoscopies for diagnostic purposes. Patients were randomized into two groups, with 18 patients (Group I) receiving a single oral dose of 400 mg lomefloxacin and 18 patients (Group II) receiving 400 mg twice daily. Samples of serum and bronchial secretions were collected simultaneously in both groups at 1, 2, or 4 hours after lomefloxacin administration. The results of this study showed that bronchial penetration of lomefloxacin was rapid and yielded high concentrations; the mean bronchial levels of the drug reached 2.78 +/- 3.64 micrograms/mL in Group I 1 hour after the dose, and 2.84 +/- 1.73 micrograms/mL in Group II at the fourth hour. The ratio between bronchial and simultaneous serum concentrations was 89% at the first and second hours after the dose for Group I, and it was 77% 4 hours after oral administration in Group II. In comparing these results to previous reports of lomefloxacin penetration into bronchial mucosa or of concentrations of other new fluoroquinolones into bronchial secretions, it is to be noted that the local concentrations of the newer quinolones are of very similar values, ranging from 2.7 micrograms/mL (ofloxacin) to 4.46 micrograms/mL (pefloxacin). This study confirms that lomefloxacin achieves high tissue concentrations in the respiratory tree; this characteristic, together with lomefloxacin's antibacterial spectrum, indicates promise in the treatment of many respiratory infections.

Effect of bromhexeine on sputum amoxycillin levels in lower respiratory infections

Bromhexeine has been widely used as an adjunct in the management of lower respiratory infections and is useful in altering the physical characteristics of sputum. Its effect on the sputum penetration of an antibiotic has been sparsely studied. The present study highlights the improvement in sputum amoxycillin (amoxy) levels when a combination tablet, amoxy 500 mg plus bromhexeine 8 mg, is administered as compared to plain amoxy 500 mg. Sputum amoxy levels were significantly higher in the combination group (0.674 +/- 0.588 micrograms ml-1) as compared to 0.272 +/- 0.19 micrograms ml-1 in the amoxy group (P = 0.028). The clinical responses assessed by the physician as well as the patient were significantly better in the amoxy plus bromhexeine group as compared to the amoxy group. The radiological and bacteriological responses were similar in both groups. There was no increase in the side-effects due to bromhexeine and, overall, its use can be recommended in the treatment of acute lower respiratory infections.

The use of probenecid to increase the serum amoxycillin levels in patients with bronchiectasis

Amoxycillin 3 g twice daily is effective in treating patients with bronchiectasis who have daily purulent sputum. However, it is a relatively expensive treatment if used for prolonged periods. This pilot study in six patients with bronchiectasis showed that the concurrent administration of probenecid with a smaller dose of amoxycillin produced similar clinical responses and pharmacokinetic profiles to those found with high dose amoxycillin alone. The amount of amoxycillin used was reduced by two thirds, producing a potential saving of approximately pound 1000 per patient per annum in those taking long term treatment.

Penicillin concentration in saliva and its influence on bacterial interference

The aim of the investigation was to study the influence of various penicillin levels on the interference between alfa- and beta-streptococci based on antibiotic levels registered after oral intake of penicillin tablets. It was found that penicillin was released from ordinary sugar coated tablets already in the mouth resulting in concentrations in saliva above the MIC of most penicillin sensitive microorganisms during the first 2 min. This was followed by a decrease of the alfa-streptococcal flora. It was also shown that penicillin levels above the MIC of alfa-streptococci resulted in prolonged survival of beta-streptococci as compared to that noted at penicillin levels above the MIC of beta-streptococci but below that of the alfa-strains. At this latter level a synergistic effect between penicillin and interfering alfa-streptococcal strains could be demonstrated.

The clinical relevance of protein binding and tissue concentrations in antimicrobial therapy

The relevance of protein binding, molecular size and lipophilicity to tissue penetration of antimicrobials is discussed, and the clinical relevance of tissue penetration of these agents is assessed. In order to assess the relevance of any factor on the clinical outcome of a group of infections it is necessary to obtain some form of dose response; i.e. the dose has to be (intentionally or otherwise) titrated down until negative responses are seen. Information on clinical failures tends not to be reported, hence useful data are difficult to obtain. The relevance of protein binding to the microbiological activity of a drug is important and the use of some highly bound agents in readily assessable diseases is illustrated with a few examples: the poor efficacy of fusidic acid in gonorrhoea, when high failure rates are found with doses of 2g; ceftriaxone in gonorrhoea, at doses (25mg) with which one would expect cures, is associated with significant failures; the failure of cefoperazone in serious illness can be related to the degree of protein binding. The degree of tissue penetration (protein binding apart) is related to clinical efficacy in urinary tract infections (where ample evidence is available), chest infections (where the data are somewhat fewer but probably convincing) and meningitis where experimental data are firm but clinical information less readily available.

A comparative study of amoxycillin and pivampicillin in persistent Haemophilus influenzae infection of the lower respiratory tract in children with chronic lung disease

A double-blind cross-over study was undertaken to compare the efficacy of amoxycillin and pivampicillin on Haemophilus influenzae infection of the lower respiratory tract in children. 20 patients with cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD) due to other causes were included in the study. All patients had a history of regularly harbouring H. influenzae in sputum and repeated treatment failures with pivampicillin. 18 completed two 14-day courses in random order with equimolar doses of pivampicillin (80 mg/kg/day) and amoxycillin (62 mg/kg/day). Both drugs were well tolerated with no serious side effects, but pivampicillin was associated with more pronounced nausea. In steady state the mean serum concentrations of antibiotics 2 and 4 h after medication were 9.7 and 3.7 micrograms/ml for pivampicillin and 19.1 and 7.9 micrograms/ml for amoxycillin (p less than 0.01). Eradication of H. influenzae and clinical improvement was seen in one-third of the courses with both drugs. Betalactamase producing ampicillin-resistant strains emerged during 58% of the amoxycillin courses, but only in 16% of the pivampicillin courses (p less than 0.001). The high number of treatment failures and the development of resistant strains indicate that betalactamase inhibitors may possibly improve the efficacy of these drugs, especially of amoxycillin, in these patients.

Antibiotic use in cystic fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the beta-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

A review of the therapeutic efficacy of aerosolized and endotracheally instilled antibiotics

Achievement of sufficient concentrations of aerosolized antibiotic at the site of infection is limited by technical problems in antibiotic delivery and by drug inactivation. Antibiotic delivery by aerosolization is generally associated with minimal systemic absorption, whereas systemic absorption may be significant after endotracheal instillation. Methodologic problems make correlations between clinical response and sputum antibiotic concentrations difficult. Studies suggest that aerosolized antibiotics are of little value in the treatment of chronic bronchopulmonary infections. Endotracheal instillation appears to be associated with favorable clinical responses, possibly due to enhanced antibiotic delivery to the site of infection. Prophylactic aerosolized antibiotics are effective in altering sputum flora; reduction in mortality from acquired pneumonia has not been demonstrated. The development of resistant organisms may occur as a result of prophylactic treatment.

Serum, saliva, and sputum levels of metronidazole in acute exacerbations of chronic bronchitis

We have evaluated the absorption and the penetration of metronidazole into the bronchial secretions and saliva in acute infective exacerbations of chronic bronchitis. Seventeen patients were given 400 mg orally three times daily for seven days and "steady state" levels were measured in serum, saliva, and sputum on the last day of treatment. Mean levels in the three biological fluids were not significantly different. Higher metronidazole levels in sputum tended to occur in patients with higher serum levels. In all but one patient, levels in serum and saliva were well within the therapeutic range. We conclude that this oral regimen results in therapeutic tissue levels in acute exacerbations of chronic bronchitis.

Human pharmacokinetics and disposition of sarmoxicillin, a lipophilic amoxicillin prodrug

Sarmoxicillin, an amoxicillin prodrug, is the methoxymethyl ester of hetamoxicillin. Esterification converted amoxicillin from an amphoteric to a cationic compound and resulted in a 30- to 600-fold increase in lipid partitioning. Oral absorption studies in normal subjects demonstrated that sarmoxicillin was only partially hydrolyzed by nonenzymatic and gut or hepatic first-pass metabolism and that significant quantities of intact ester appeared in the systemic circulation. Sarmoxicillin was converted to amoxicillin in plasma by hydrolysis of the acetone penicinate and the methoxymethyl ester bonds. Significant amoxicillin levels were demonstrated in saliva after administration of sarmoxicillin, but not amoxicillin, over a 250- to 1,000-mg dose range. Differences in the absorption, distribution, or metabolism of amoxicillin were also evident in the lower plasma amoxicillin maximum concentration and area under the curve and longer half-life after sarmoxicillin administration. Differences in the distribution of this lipophilic ester could result in a significant increase in tissue penetration and subsequent therapeutic efficacy of amoxicillin when administered as sarmoxicillin.

Plasma and sputum erythromycin concentrations in chronic bronchitis

Plasma and sputum concentrations of erythromycin were measured in 10 patients with chronic bronchitis during an eight-day course of a new formulation of erythromycin stearate. The plasma erythromycin levels compared favourably with the minimal inhibitory concentrations for common respiratory pathogens and indicated adequate gastrointestinal absorption when the drug was taken immediately before food. Sputum erythromycin levels were variable and in some patients low or undetectable. Measurable sputum erythromycin levels were approximately 10% of plasma levels with no evidence of accumulation and were of similar order of magnitude to the minimal inhibitory concentrations for common respiratory pathogens except Haemophilus influenzae. There was no correlation between sputum and plasma erythromycin levels. There was a trend for higher erythromycin levels in sputum containing increasing amounts of pus and also when plasma levels increased.

Bacterial kill rates of amoxycillin and ampicillin at exponentially diminishing concentrations simulating in vivo conditions

The responses of bacteria exposed to amoxycillin and ampicillin were studied at continuously decreasing levels with half-life values similar to those which could occur in vivo. For Escherichia coli, the kill-rates were higher with amoxycillin than with ampicillin. The bactericidal response was exponential. With an antibiotic half-life of one hour, the amoxycillin first order inactivation rate was 3.544 h-1 and the viable cell half-life was 0.196 h; the respective values for ampicillin were 2.341 h-1 and 0.296 h. With an antibiotic half-life of five hours, the inactivation rate was 0.704 h-1 corresponding to a viable cell half-life of 0.985 h for amoxycillin compared to 0.358 h-1 and 1.937 h respectively for ampicillin. Comparison of viable counts and photometric monitoring showed that the former is the preferable method for recording the bacterial response to these beta-lactam antibiotics. During the phase of exponential kill, a plateau occurred in the optical density values. This was due in part to an increased biomass per cell. During the recovery phase, the number of viable cells started to increase several hours sooner than did the rise in optical density. For Staphylococcus aureus,the rates of kill were similar with both agents. Amoxycillin had a long bacteriostatic phase which was not seen with ampicillin. This led to a longer lasting antibacterial effect and reduction to a lower total count with amoxycillin. With staphylococci, the viable counts and the photometric responses were parallel.

Amoxycillin injectable: a review of its antibacterial spectrum, pharmacokinetics and therapeutic use

Amoxycillin, an acid stable semisynthetic penicillin shown to be effective against a wide range of infections when given orally, is now available for intramuscular and intravenous injection. Amoxycillin has an antibacterial spectrum and level of activity essentially the same as for ampicillin. Amoxycillin has been shown to have more rapid and complete bactericidal action than ampicillin against E. coli in vitro and in animal models of infection, but the clinical importance of this difference has not yet been determined. Amoxycillin is present in therapeutic amounts in the cerebrospinal fluid of meningitis patients given the drug intravenously and parenteral amoxycillin has been successfully used in the treatment of meningitis, and in urinary tract infections, septicaemia, upper and lower respiratory tract infections and a variety of other infections caused by Gram-negative and Gram-positive aerobic bacteria. However, the extent of experience is limited compared with ampicillin, and thus further studies are needed to more clearly delineate its relative therapeutic role. Parenteral amoxycillin is generally well tolerated. Pain at the site of intramuscular injection occurs in about one-third of patients, but can be minimised by the use of lignocaine or procaine hydrochloride.

Plasma and saliva concentrations for a new formulation of erythromycin stearate

Erythromycin saliva and plasma concentrations were determined in 10 subjects after the first and fourth doses of a new formulation of erythromycin stearate ('Erythrocin'), 500 mg 8-hourly, taken immediately before food. Consistent absorption occurred and the steady state plasma levels compared favourably with the minimal inhibitory concentrations of erythromycin for common respiratory pathogens. There was a significant positive correlation between steady state saliva and plasma levels.

Antibiotic concentrations in saliva of purulent parotitis

In patients with unilateral acute purulent parotitis treated with penicillin and doxycycline the antibiotic concentration was determined in plasma and saliva from both the healthy and the affected parotid gland. The results show that the penicillin concentrations in purulent saliva of the diseased gland is considerably higher than in non-purulent saliva of the healthy parotid gland. There was no such marked difference in concentrations of doxycycline. The possible mechanisms behind these observations are discussed as are the conclusions that can be drawn concerning treatment of acute purulent and chronic recurrent parotitis.

Doxycycline in serum and bronchial secretions

The concentration of doxycycline hydrochloride was measured in serum and bronchial secretions in five patients with chronic bronchitis receiving doxycycline orally in normal therapeutic dosage for seven days (200 mg day 1, 100 mg days 2 to 7). After the loading dose of 200 mg, serum concentrations ranged between 5-40 and 3-45 mug/ml (mean 4-33 mug/ml) at 3 hours, declining to between 2-28 and 1-21 mug/ml (mean 1-71 mug/ml) at 23 hours. The mean serum levels for days 2 to 7 were 2-15, 1-79, and 1-38 at 3, 8, and 23 hours respectively. There was considerable individual variability and a wide range of concentrations of doxycycline in the sputum (0-07 to 2-10 mug/ml, mean 0-34 mug/ml). During the course of treatment there was a progressive increase in sputum levels and sputum/serum concentration ratios. There was no correlation between sputum concentration and degree of purulence. The clinical efficacy of doxycycline does not appear to be related to sputum concentration, although the progressive increase in sputum doxycycline levels may be relevant in preventing recurrence of acute infection when the drug is administered as long-term prophylactic therapy.

Sputum and serum levels of amoxycillin in chronic bronchial infections

A study of 11 patients suffering from acute exacerbations of chronic bronchial infection, all with purulent (Mp+++) sputum, showed that good penetration of amoxycillin into such sputum occurs. The levels of amoxycillin in sputum doubled proportionally with the oral dose, at least up to dosages of 2 g. High dosages or oral amoxycillin may therefore, be advantageous in the treatment of chronic bronchial infection. In a study of 30 chronic bronchitic patients, whose sputum varied in purulence from mucoid to purulent (Mp+++) the concentration of amoxycillin in sputum containing approximately 50% pus (Mp++) was significantly higher than that in any other degree of purulence. These results indicate that amoxycillin penetrates best into sputum at an intermediate degree of purulence.

Amoxycillin: A review of its antibacterial and pharmacokinietic properties and therapeutic use

Amoxycillin2 is an acid stable semisynthetic penicillin closely related to ampicillin. Unlike pivampicillin and hetacillin, amoxycillin is not converted to ampicillin in the body. The antibacterial spectrum and level of activity of amoxycillin is essentially the same as for ampicillin, and there is complete cross-resistance between the two drugs. After oral administration, amoxycillin is better absorbed than ampicillin. Mean peak serum levels of amoxycillin are generally twice those of ampicillin after an equal dose. The better absorption and penetration into certain body tissues and fluids of amoxycillin and its greater activity against experimental infections in mice, suggest that it might be preferred to ampicillin in the treatment of some infections, but any clear superiority over ampicillin in clinical practice has yet to be demonstrated. However, these properties have enabled amoxycillin to be given at half the dose of ampicillin without loss of therapeutic efficacy, and the princpal side-effects of skin rashes and diarrhoea have tended to be less frequent with amoxycillin than with ampicillin. Other side-effects are essentially similar in nature to those reported with ampicillin.