Amoxicillin: in vitro and pharmacological studies

Assessing city-wide pharmaceutical emissions to wastewater via modelling and passive sampling

With increasing numbers of chemicals used in modern society, assessing human and environmental exposure to them is becoming increasingly difficult. Recent advances in wastewater-based epidemiology enable valuable insights into public exposure to data-poor compounds. However, measuring all >26,000 chemicals registered under REACH is not just technically unfeasible but would also be incredibly expensive. In this paper, we argue that estimating emissions of chemicals based on usage data could offer a more comprehensive, systematic and efficient approach than repeated monitoring. Emissions of 29 active pharmaceutical ingredients (APIs) to wastewater were estimated for a medium-sized city in the Netherlands. Usage data was collected both on national and local scale and included prescription data, usage in health-care institutions and over-the-counter sales. Different routes of administration were considered as well as the excretion and subsequent in-sewer back-transformation of conjugates into respective parent compounds. Results suggest model-based emission estimation on a city-level is feasible and in good agreement with wastewater measurements obtained via passive sampling. Results highlight the need to include excretion fractions in the conceptual framework of emission estimation but suggest that the choice of an appropriate excretion fraction has a substantial impact on the resulting model performance.

Catalyst-Free Amino-Yne Click Reaction: An Efficient Way for Immobilizing Amoxicillin onto Polymeric Surfaces

Surface modifications play a crucial role in enhancing the functionality of biomaterials. Different approaches can be followed in order to achieve the bioconjugation of drugs and biological compounds onto polymer surfaces. In this study, we focused on the immobilization of an amoxicillin antibiotic onto the surface of poly-L-lactic acid (PLLA) using a copper-free amino-yne click reaction. The utilization of this reaction allowed for a selective and efficient bioconjugation of the amoxicillin moiety onto the PLLA surface, avoiding copper-related concerns and ensuring biocompatibility. The process involved sequential steps that included surface activation via alkaline hydrolysis followed by an amidation reaction with ethylendiamine, functionalization with propiolic groups, and subsequent conjugation with amoxicillin via a click chemistry approach. Previous amoxicillin immobilization using tryptophan and fluorescent amino acid conjugation was carried out in order to determine the efficacy of the proposed methodology. Characterization techniques such as X-ray photoelectron spectroscopy (XPS), Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) spectroscopy, surface imaging, water contact angle determination, and spectroscopic analysis confirmed the successful immobilization of both tryptophan and amoxicillin while maintaining the integrity of the PLLA surface. This tailored modification not only exhibited a novel method for surface functionalization but also opens avenues for developing antimicrobial biomaterials with improved drug-loading capacity.

Simultaneous monitoring of amoxicillin and paracetamol in synthetic biological fluids using a 3D printed disposable electrode with a lab-made conductive filament

In this work, we are pleased to present for the first time a 3D-printed electrochemical device using a lab-made conductive filament based on graphite (Gr) and polylactic acid (PLA) polymer matrix for the simultaneous detection of amoxicillin (AMX) and paracetamol (PAR). The sensor was properly characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Compared to the commercial glassy carbon electrode (GCE), the superior performance of the 3D-Gr/PLA electrode was verified with a 3.8-fold more favored charge transfer. A differential pulse voltammetry (DPV) method was proposed providing a linear working range of 4 to 12 μmol L-1 for both analytes and a limit of detection (LOD) of 0.80 and 0.51 μmol L-1 for AMX and PAR, respectively. Additionally, repeatability studies (n = 5, RSD < 5.7%) indicated excellent precision, and recovery percentages ranging from 89 to 109% when applied to synthetic human urine, saliva, and plasma samples, attested to the accuracy of the method. The studies also indicate that the sensor does not suffer significant interference from common substances (antibiotics and biomarkers) present in the biological fluids, which makes it a promising analytical tool considering its low-cost, ease of manufacturing, robustness, and electrochemical performance.

Physiologically based pharmacokinetic modeling to assess the drug-drug interactions of anaprazole with clarithromycin and amoxicillin in patients undergoing eradication therapy of H. pylori infection

OBJECTIVE

This study aimed to assess the pharmacokinetic (PK) interactions of anaprazole, clarithromycin, and amoxicillin using physiologically based pharmacokinetic (PBPK) models.

METHODS

The PBPK models for anaprazole, clarithromycin, and amoxicillin were constructed using the GastroPlus™ software (Version 9.7) based on the physicochemical data and PK parameters obtained from literature, then were optimized and validated in healthy subjects to predict the plasma concentration-time profiles of these three drugs and assess the predictive performance of each model. According to the analysis of the properties of each drug, the developed and validated models were applied to evaluate potential drug-drug interactions (DDIs) of anaprazole, clarithromycin, and amoxicillin.

RESULTS

The developed PBPK models properly described the pharmacokinetics of anaprazole, clarithromycin, and amoxicillin well, and all predicted PK parameters (Cmax,ss, AUC0-τ,ss) ratios were within 2.0-fold of the observed values. Furthermore, the application of these models to predict the anaprazole-clarithromycin and anaprazole-amoxicillin DDIs demonstrates their good performance, with the predicted DDI Cmax,ss ratios and DDI AUC0-τ,ss ratios within 1.25-fold of the observed values, and all predicted DDI Cmax,ss, and AUC0-τ,ss ratios within 2.0-fold. The simulated results show no need to adjust the dosage when co-administered with anaprazole in patients undergoing eradication therapy of H. pylori infection since the dose remained in the therapeutic range.

CONCLUSION

The whole-body PBPK models of anaprazole, clarithromycin, and amoxicillin were built and qualified, which can predict DDIs that are mediated by gastric pH change and inhibition of metabolic enzymes, providing a mechanistic understanding of the DDIs observed in the clinic of clarithromycin, amoxicillin with anaprazole.

Combination of Amoxicillin 3000 mg and Probenecid Versus 1500 mg Amoxicillin Monotherapy for Treating Syphilis in Patients With Human Immunodeficiency Virus: An Open-Label, Randomized, Controlled, Non-Inferiority Trial

BACKGROUND

Amoxicillin plus probenecid is an alternative to intramuscular benzathine penicillin G for treating syphilis in the United Kingdom. Low-dose amoxicillin is an alternative treatment option used in Japan.

METHODS

We conducted an open-label, randomized, controlled, non-inferiority trial between 31 August 2018, and 3 February 2022, to compare 1500 mg low-dose amoxicillin monotherapy with the combination of 3000 mg amoxicillin and probenecid (non-inferiority margin 10%). Patients with human immunodeficiency virus (HIV) infection and syphilis were eligible. The primary outcome was the cumulative serological cure rate within 12 months post-treatment, measured using the manual rapid plasma reagin card test. Secondary outcomes included safety assessment.

RESULTS

A total of 112 participants were randomized into 2 groups. Serological cure rates within 12 months were 90.6% and 94.4% with the low-dose amoxicillin and combination regimens, respectively. Serological cure rates for early syphilis within 12 months were 93.5% and 97.9% with the low-dose amoxicillin and combination regimens, respectively. Non-inferiority of low-dose amoxicillin compared with amoxicillin plus probenecid overall and for early syphilis was not confirmed. No significant side effects were detected.

CONCLUSIONS

This is the first randomized controlled trial to demonstrate a high efficacy of amoxicillin-based regimens for treating syphilis in patients with HIV infection, and the non-inferiority of low-dose amoxicillin compared with amoxicillin plus probenecid was not seen. Therefore, amoxicillin monotherapy could be a good alternative to intramuscular benzathine penicillin G with fewer side effects. However, further studies comparing with benzathine penicillin G in different populations and with larger sample sizes are needed.

TRIALS REGISTRATION

(UMIN000033986).

Clinical evidence of human pathogens implicated in Alzheimer's disease pathology and the therapeutic efficacy of antimicrobials: an overview

A wealth of pre-clinical reports and data derived from human subjects and brain autopsies suggest that microbial infections are relevant to Alzheimer's disease (AD). This has inspired the hypothesis that microbial infections increase the risk or even trigger the onset of AD. Multiple models have been developed to explain the increase in pathogenic microbes in AD patients. Although this hypothesis is well accepted in the field, it is not yet clear whether microbial neuroinvasion is a cause of AD or a consequence of the pathological changes experienced by the demented brain. Along the same line, the gut microbiome has also been proposed as a modulator of AD. In this review, we focus on human-based evidence demonstrating the elevated abundance of microbes and microbe-derived molecules in AD hosts as well as their interactions with AD hallmarks. Further, the direct-purpose and potential off-target effects underpinning the efficacy of anti-microbial treatments in AD are also addressed.

Aminopenicillins versus Non-aminopenicillins for Treatment of Enterococcal Lower Urinary Tract Infections

Aminopenicillins achieve urinary concentrations that exceed typical minimum inhibitory concentrations for enterococcal lower urinary tract infection (UTI). Our clinical microbiology laboratory discontinued routine susceptibilities on enterococcal urine isolates and reports "aminopenicillins are predictably reliable for uncomplicated enterococcal UTI". The study objective was to compare outcomes of aminopenicillins (AP) to non-aminopenicillins (NAP) for enterococcal lower UTIs. This was an IRB approved, retrospective cohort of adults hospitalized with symptomatic enterococcal lower UTIs from 2013-2021. Primary endpoint: composite clinical success at 14-days, defined as resolution of symptoms without new symptoms and no repeat culture growth of index organism. A non-inferiority analysis was utilized with a 15% margin, and logistic regression evaluated characteristics associated with 14-day failure. 178 subjects were included: 89 AP, 89 NAP. VRE was identified in 73 (82%) AP and 76 (85%) NAP patients (P=0.54); a total of 34 (38.2%) AP and 66 (74.2%) NAP patients had confirmed E. faecium (P<0.001). Amoxicillin (36, 40.5%) and ampicillin (36, 40.5%) were the most frequent AP utilized; linezolid (41, 46%) and fosfomycin (30, 34%) were the most frequent NAP. 14-day clinical success for AP and NAP was 83.1% and 82.0% (1.1% difference, 97.5%CI, -0.117-0.139). Among the E. faecium subgroup, 14-day clinical success was observed in 27/34 (79.4%) of AP and 53/66 (80.3%) of NAP patients (P=0.916). In logistic regression, APs were not associated with 14-day clinical failure (adjOR 0.84; 95%CI, 0.38-1.86). Aminopenicillins were noninferior to non-aminopenicillins for treating enterococcal lower UTIs and may be considered irrespective of susceptibility results.

Effect of unintended short-term 3.0 g/day amoxicillin and probenecid treatment for early syphilis on patients with HIV-1 infection

Background

Standard therapy for early syphilis involves intramuscular injections of penicillin G, which frequently faces shortages in several countries. Fourteen-day amoxicillin therapy has been suggested as an alternative to benzathine penicillin G, but the optimal duration of amoxicillin therapy remains unclear and could theoretically be shortened to less than 14 days. The aim of this study was to explore the effectiveness of short-term amoxicillin therapy for early syphilis.

Methods

We retrospectively explored the effectiveness of short-term amoxicillin therapy for early syphilis. The treatment data of patients who had received amoxicillin therapy for less than 14 days for unintended reasons were reviewed. Diagnosis was confirmed based on either the physician's description or clinical presentation. Successful treatment was defined as a fourfold or greater decline in the rapid plasma reagin titer or sero-reversion to negative within 12 months.

Results

Of 295 patients, 8 received short-term amoxicillin treatment. All were men who had sex with men and people living with human immunodeficiency virus. Their median age, CD4 count, and treatment duration were 34 years (range, 26-40), 258/mL (range, 112-930), and 9.5 days (range, 5-11), respectively. One patient had primary syphilis, six had secondary syphilis, and one had early latent syphilis. All patients, except one who showed reinfection, demonstrated a serological response within 4 months. The median time for serological response was 112 days.

Conclusion

The results indicate that early syphilis could potentially be treated with 5-11 days of amoxicillin therapy combined with probenecid. This suggests that short-term amoxicillin therapy might be a sufficient treatment for early syphilis instead of the standard 14-day course.

Impact of Antibiotics as Waste, Physical, Chemical, and Enzymatical Degradation: Use of Laccases

The first traces of Tetracycline (TE) were detected in human skeletons from Sudan and Egypt, finding that it may be related to the diet of the time, the use of some dyes, and the use of soils loaded with microorganisms, such as Streptomyces spp., among other microorganisms capable of producing antibiotics. However, most people only recognise authors dating between 1904 and 1940, such as Ehrlich, Domagk, and Fleming. Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments (pharmaceutics, hospitals, senior residences) and their irrational use in humans and animals. The main antibiotics problem lies in delivered and non-prescribed human use, use in livestock as growth promoters, and crop cultivation as biocides (regulated activities that have not complied in some places). This practice has led to the toxicity of the environment as antibiotics generate eutrophication, water pollution, nutrient imbalance, and press antibiotic resistance. In addition, the removal of antibiotics is not a required process in global wastewater treatment standards. This review aims to raise awareness of the negative impact of antibiotics as residues and physical, chemical, and biological treatments for their degradation. We discuss the high cost of physical and chemical treatments, the risk of using chemicals that worsen the situation, and the fact that each antibiotic class can be transformed differently with each of these treatments and generate new compounds that could be more toxic than the original ones; also, we discuss the use of enzymes for antibiotic degradation, with emphasis on laccases.

Aminopenicillins for treatment of ampicillin-resistant enterococcal urinary tract infections

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

The purpose of this review is to describe the theory behind and data supporting use of aminopenicillins in the treatment of ampicillin-resistant enterococcal urinary tract infections.

SUMMARY

Aminopenicillin concentrations in the urine may be high enough to achieve bacterial eradication and clinical cure for infections affecting the lower genitourinary tract, even in the context of in vitro resistance based on established susceptibility breakpoints. A literature search was conducted to identify original research articles describing the use of aminopenicillins in the treatment of urinary tract infections caused by ampicillin-resistant Enterococcus species. Three published retrospective cohort studies were identified, all of which reported that aminopenicillins had similar rates of clinical cure as other antibiotic classes prescribed for the treatment of enterococcal urinary tract infections.

CONCLUSION

Both pharmacokinetic/pharmacodynamic principles and limited retrospective clinical data support the use of aminopenicillins in the treatment of lower urinary tract infections caused by Enterococcus species, even when the isolates have a minimum inhibitory concentration that exceeds the susceptibility breakpoint.

Antibiotic Utilization and Efficacy Associated With Treating Pediatric Urinary Tract Infections in Texas Medicaid Patients in the First Year of Life

BACKGROUND

Historically, amoxicillin (Amoxil) has been used as a first-line agent to treat pediatric urinary tract infections (UTIs). However, emerging antibiotic resistance in urinary pathogens has led to broader treatment options, such as cefdinir (Omnicef). This shift in prescribing practices is predicted to vary among place of service and gender due to differing institutional protocols and antimicrobial stewardship practices.

OBJECTIVE

This study aimed to describe the antibiotic utilization patterns associated with treating pediatric UTIs in Texas Medicaid patients and to assess the real-world efficacy of the antibiotics that were prescribed.

METHODS

Texas Medicaid prescription and medical claims data for patients under 1 year of age were included in the analysis if they presented with a UTI to the healthcare practitioner’s office or the emergency department (ED) and were treated with an outpatient antibiotic. Treatment efficacy was assessed by whether a patient received a second (different) antibiotic within 7 days of their initial antibiotic fill.

RESULTS

A total of 12,795 visits met inclusion criteria; 12,561 visits included prescriptions for the top 4 antibiotics prescribed: cefdinir (50%), amoxicillin (25%), cephalexin (Keflex; 13%), and amoxicillin-clavulanate (Augmentin; 12%). Cefdinir utilization predominated in both places of service [office (50%) and ED (55%)], and gender [males (47%) and females (52%)]. Controlling for gender and place of service, initial treatment with amoxicillin when compared with cefdinir (OR = 2.54; 95% confidence intervals: 1.84–3.54; P < 0.001) was associated with a greater rate of treatment failure.

CONCLUSIONS

In this study of Texas Medicaid patients, the widespread utilization of cefdinir may be appropriate for the empiric treatment of uncomplicated UTIs because of its low rate of treatment failure compared to other commonly used antibiotics.

The effect of antimicrobial treatment on mortality associated with urinary tract disease in mink kits (Neovison vison)

Mink urinary tract disease (MUTD) often presents as urolithiasis and/or cystitis and is known as an important cause of mortality in mink kits during the early growth season. Antimicrobial flock treatment has been routinely applied as preventive/therapeutic protocol on Danish mink farms with increased mortality associated with MUTD. The therapeutic effect of this treatment strategy has not previously been investigated. In this study, we applied controlled parallel group treatment trials to assess the effect of sulfadiazine/trimethoprim and amoxicillin treatment on mortality associated with MUTD in mink kits. On farm A, eight mink kits were diagnosed with MUTD post mortem in the treatment group (n = 1920, sulfadiazine/trimethoprim treatment: 30 mg/kg, q 24 h, P.O for 5 days) compared to 16 in the untreated control group (n = 1920). No significant difference in mortality associated with MUTD were found between  the treatment and the control group using the Fisher’s exact test (P = 0.15). Treatment group 2 (n = 1920, amoxicillin treatment: 14 mg/kg q 24 h, P.O for 5 days) and treatment group 3 (n = 2088, amoxicillin treatment: 7.5 mg/kg q 24 h, P.O for 5 days) were investigated on farm B. Eight and four mink kits were diagnosed with MUTD post mortem in group 2 and 3, respectively. No difference between occurrence of MUTD were found between the control group and treatment group 2 (P = 0.42) or treatment group 3 (P = 0.75). No significant difference between final body weights or weight gain were found between treatment and control weighing groups on farm A or B. In conclusion, antimicrobial treatment administered in the feed showed no significant effect on weight gain or mortality associated with MUTD on the farms included in this study.

Short-Term Amoxicillin-Induced Perturbation of the Gut Microbiota Promotes Acute Intestinal Immune Regulation in Brown Norway Rats

The intestinal gut microbiota is essential for maintaining host health. Concerns have been raised about the possible connection between antibiotic use, causing microbiota disturbances, and the increase in allergic and autoimmune diseases observed during the last decades. To elucidate the putative connection between antibiotic use and immune regulation, we have assessed the effects of the antibiotic amoxicillin on immune regulation, protein uptake, and bacterial community structure in a Brown Norway rat model. Daily intra-gastric administration of amoxicillin resulted in an immediate and dramatic shift in fecal microbiota, characterized by a reduction of within sample (α) diversity, reduced variation between animals (β diversity), increased relative abundance of Bacteroidetes and Gammaproteobacteria, with concurrent reduction of Firmicutes, compared to a water control group. In the small intestine, amoxicillin also affected microbiota composition significantly, but in a different way than observed in feces. The small intestine of control animals was vastly dominated by Lactobacillus, but this genus was much less abundant in the amoxicillin group. Instead, multiple different genera expanded after amoxicillin administration, with high variation between individual animals, thus the small intestinal α and β diversity were higher in the amoxicillin group compared to controls. After 1 week of daily amoxicillin administration, total fecal IgA level, relative abundance of small intestinal regulatory T cells and goblet cell numbers were higher in the amoxicillin group compared to controls. Several bacterial genera, including Escherichia/Shigella, Klebsiella (Gammaproteobacteria), and Bifidobacterium, for which the relative abundance was higher in the small intestine in the amoxicillin group than in controls, were positively correlated with the fraction of small intestinal regulatory T cells. Despite of epidemiologic studies showing an association between early life antibiotic consumption and later prevalence of inflammatory bowel diseases and food allergies, our findings surprisingly indicated that amoxicillin-induced perturbation of the gut microbiota promotes acute immune regulation. We speculate that the observed increase in relative abundance of small intestinal regulatory T cells is partly mediated by immunomodulatory lipopolysaccharides derived from outgrowth of Gammaproteobacteria.

Oral amoxicillin and amoxicillin-clavulanic acid: properties, indications and usage

BACKGROUND

Amoxicillin has been in use since the 1970s; it is the most widely used penicillin both alone and in combination with the β-lactamase clavulanic acid.

OBJECTIVES

In this narrative review, we re-examine the properties of oral amoxicillin and clavulanic acid and provide guidance on their use, with emphasis on the preferred use of amoxicillin alone.

SOURCES

Published medical literature (MEDLINE database via Pubmed).

CONTENT

While amoxicillin and clavulanic acid have similar half-lives, clavulanic acid is more protein bound and even less heat stable than amoxicillin, with primarily hepatic metabolism. It is also more strongly associated with gastrointestinal side effects, including Clostridium difficile infection, and, thus, in oral combination formulations, limits the maximum daily dose of amoxicillin that can be given. The first ratio for an amoxicillin-clavulanic acid combination was set at 4:1 due to clavulanic acid's high affinity for β-lactamases; ratios of 2:1, 7:1, 14:1 and 16:1 are currently available in various regions. Comparative effectiveness data for the different ratios are scarce. Amoxicillin-clavulanic acid is often used as empiric therapy for many of the World Health Organization's Priority Infectious Syndromes in adults and children, leading to extensive consumption, when some of these syndromes could be handled with a delayed antibiotic prescription approach or amoxicillin alone.

IMPLICATIONS

Using available epidemiological and pharmacokinetic data, we provide guidance on indications for amoxicillin versus amoxicillin-clavulanic acid and on optimal oral administration, including choice of combination ratio. More data are needed, particularly on heat stability, pharmacodynamic effects and emergence of resistance in 'real-world' clinical settings.

Phenoxymethylpenicillin Versus Amoxicillin for Infections in Ambulatory Care: A Systematic Review

Most antibiotics are prescribed in primary care, and commonly for respiratory tract infections (RTIs). Narrow-spectrum phenoxymethylpenicillin is the antibiotic of choice for RTIs in the Scandinavian countries, while broader spectrum amoxicillin is used in most other European countries. This review summarizes the knowledge of the effect of phenoxymethylpenicillin versus amoxicillin for infections treated in ambulatory care. We searched PubMed/Medline and Embase for trials comparing the clinical effect of phenoxymethylpenicillin and amoxicillin. The Norwegian Knowledge Centre for the Health Services’ checklist was used to assess risk of bias. In total, 1687 studies were identified, and 18 of these fulfilled the inclusion criteria. One additional study was found as a reference. The randomized controlled trials revealed no significant differences in clinical effect in acute sinusitis (three RCTs), GAS tonsillitis (11 RCTs) and Lyme borreliosis (two RCTs). One RCT on community-acquired pneumonia found amoxicillin to be superior, while the results were conflicting in the two RCTs on acute otitis. The results suggest that non-Scandinavian countries should consider phenoxymethylpenicillin as the treatment of choice for RTIs because of its narrower spectrum. More studies should be conducted on the clinical effect of phenoxymethylpenicillin versus amoxicillin for acute otitis and lower RTIs.

Active Site Mapping of an Aspartic Protease by Multiple Fragment Crystal Structures: Versatile Warheads To Address a Catalytic Dyad

Crystallography is frequently used as follow-up method to validate hits identified by biophysical screening cascades. The capacity of crystallography to directly screen fragment libraries is often underestimated, due to its supposed low-throughput and need for high-quality crystals. We applied crystallographic fragment screening to map the protein-binding site of the aspartic protease endothiapepsin by individual soaking experiments. Here, we report on 41 fragments binding to the catalytic dyad and adjacent specificity pockets. The analysis identifies already known warheads but also reveals hydrazide, pyrazole, or carboxylic acid fragments as novel functional groups binding to the dyad. A remarkable swapping of the S1 and S1' pocket between structurally related fragments is explained by either steric demand, required displacement of a well-bound water molecule, or changes of trigonal-planar to tetrahedral geometry of an oxygen functional group in a side chain. Some warheads simultaneously occupying both S1 and S1' are promising starting points for fragment-growing strategies.

Bioequivalence evaluation of two capsule formulations of amoxicillin in healthy adult male bangladeshi volunteers: A single-dose, randomized, open-label, two-period crossover study

BACKGROUND

Amoxicillin, a semisynthetic penicillin antibiotic, is widely prescribed in Bangladesh due to its extended spectrum and its rapid and extensive oral absorption with good tolerability. Although a number of generic oral formulations of amoxicillin are available in Bangladesh, a study of the bioequivalence and pharmacokinetic properties of these formulations has not yet been conducted in a Bangladeshi population.

OBJECTIVE

The aim of this study was to assess the pharmacokinetic properties and bioequivalence of 2 formulations of amoxicillin 500-mg capsules (test, SK-mox(®); reference, Amoxil-Bencard(®)) using serum data.

METHODS

This single-dose, randomized, open-label, 2-period crossover study was conducted in healthy male subjects in compliance with the Declaration of Helsinki and International Conference on Harmonisation guidelines. Subjects were assigned to receive the test or the reference drug as a single-dose, 500-mg capsule under fasting conditions after a 1-week washout period. After oral administration, blood samples were collected and analyzed for amoxicillin concentration using a validated high-performance liquid chromatography method. The pharmacokinetic parameters were determined using a noncompartmental method. The formulations were considered bioequivalent if the natural log-transformed ratios of pharmacokinetic parameters were within the predetermined equivalence range of 80% to 125%, according to the US Food and Drug Administration (FDA) requirement.

RESULTS

Twenty-four healthy adult male Bangladeshi volunteers (mean [SD] age, 26.92 [3.37] years; age range, 23-34 years; mean [SD] body mass index, 23.O9 [1.58] kg/m(2)) participated in the study. Using serum data, the values obtained for the test and reference formulations, respectively, were as follows: Cmax, 9.85 (2.73) and 10.63 (2.12) μg/mL; Tmax, 1.29 (0.58) and 1.33 (0.49) hours; and AUC0-12, 27.09 (7.62) and 28.56 (6.30) μg/mL · h(-1). No period, sequence, or formulation effects were observed; however, significant variation was found among subjects with regard to AUC0-12 (P < 0.001), AUC0-∞ (P = 0.002), area under the moment curve (AUMC) from 0 to 12 hours (P < 0.001), and AUMC0-∞ (P = 0.017). All CIs for the parameters measured were within the FDA-accepted limits of 80% to 125%.

CONCLUSION

The present study suggests that the test 500-mg amoxicillin capsule was bioequivalent to the reference 500-mg capsule according to the FDA regulatory definition, in this population of healthy adult male Bangladeshi volunteers.

Modulation of trichloroethylene in vitro metabolism by different drugs in human

Toxicological interactions with drugs have the potential to modulate the toxicity of trichloroethylene (TCE). Our objective is to identify metabolic interactions between TCE and 14 widely used drugs in human suspended hepatocytes and characterize the strongest using microsomal assays. Changes in concentrations of TCE and its metabolites were measured by headspace GC-MS. Results with hepatocytes show that amoxicillin, cimetidine, ibuprofen, mefenamic acid and ranitidine caused no significant interactions. Naproxen and salicylic acid showed to increase both TCE metabolites levels, whereas acetaminophen, carbamazepine and erythromycin rather decreased them. Finally, diclofenac, gliclazide, sulphasalazine and valproic acid had an impact on the levels of only one metabolite. Among the 14 tested drugs, 5 presented the most potent interactions and were selected for confirmation with microsomes, namely naproxen, salicylic acid, acetaminophen, carbamazepine and valproic acid. Characterization in human microsomes confirmed interaction with naproxen by competitively inhibiting trichloroethanol (TCOH) glucuronidation (Ki=2.329 mM). Inhibition of TCOH formation was also confirmed for carbamazepine (partial non-competitive with Ki=70 μM). Interactions with human microsomes were not observed with salicylic acid and acetaminophen, similar to prior results in rat material. For valproic acid, interactions with microsomes were observed in rat but not in human. Inhibition patterns were shown to be similar in human and rat hepatocytes, but some differences in mechanisms were noted in microsomal material between species. Next research efforts will focus on determining the adequacy between in vitro observations and the in vivo situation.

High concentrations of commonly used drugs can inhibit the in vitro glucuronidation of bisphenol A and nonylphenol in rats

4-n-Nonylphenol and bisphenol A are endocrine disrupting chemicals that are mainly detoxified through glucuronidation. A factor that may modulate their glucuronidation rates is co-exposure to pharmaceuticals. This study aimed to identify and characterize the potential metabolic interactions between 14 drugs and these two endocrine disruptors. Nonylphenol and bisphenol A were co-incubated in freshly isolated rat hepatocytes with, drugs at a high concentration. Statistically significant metabolic inhibition of bisphenol A and nonylphenol biotransformation was observed with nine drugs (>50% inhibition by naproxen, salicylic acid, carbamazepine and mefenamic acid). Inhibition assays of UGT activity in rat liver microsomes revealed: 1) competitive inhibition by naproxen (K(i)(app) = 848.3 microM) and carbamazepine (K(i)(app) = 1023.1 microM), 2) no inhibition by salicylic acid suggesting another mechanism of inhibition. Detoxification of nonylphenol and bisphenol A was shown to be impaired by excessive concentrations of many drugs and health risk assessment should therefore address this issue.

Triple crossover study on absorption and excretion of ampicillin, pivampicillin, and amoxycillin

The absorption and excretion of equivalent doses of ampicillin, pivampicillin, and amoxycillin were compared in 10 healthy volunteers after administration of these antibiotics in a randomized triple crossover fashion. As recommended, ampicillin and amoxycillin were administered on an empty stomach, whereas pivampicillin was given with breakfast. The mean half-life times were nearly identical for all three antibiotics: 60.9 min for ampicillin; 58.4 min for pivampicillin; and 62.2 min for amoxycillin. The absorption of the drugs was evaluated according to the following three criteria: the mean peak serum levels; the "area under the curve"; and the percentage of recovery in urine. By these criteria, pivampicillin was the best-absorbed drug, with absorption 3.0 to 3.6 times higher than that of ampicillin and 1.2 to 1.5 times higher than that of amoxycillin, whereas the absorption of amoxycillin was 2.1 to 2.9 times higher than that of ampicillin.

Pharmacokinetics of a new oral formulation of amoxicillin

The bioavailability of the recently developed 1 g dispersible tablet form of amoxicillin (B) and the 1 g dispersible tablet in suspension form (C) were compared to that of the 1 g standard reference formulation (A). Twelve healthy volunteers were involved in this single-dose, open, randomized, three-way cross-over study. The mean peak serum levels were 14.1 +/- 4.1 micrograms/ml after A, 15.1 +/- 3.1 micrograms/ml after B and 15.1 +/- 5.4 micrograms/ml after C. The area under the drug concentration versus time curves were 47.6 +/- 12.0 micrograms.h/ml after A, 52.8 +/- 10.2 micrograms.h/ml after B and 51.1 +/- 13.8 micrograms.h/ml after C. On the basis of these two pharmacokinetic parameters, the three formulations were found to be bioequivalent. In addition, the predicted serum concentrations during multiple dosing (3 times a day), derived from the corresponding mean concentrations after a single 1 g dose of C showed that 8 hourly administration would yield therapeutic serum concentrations for infections such as uncomplicated community-acquired pneumonia due to susceptible or less susceptible strains in otherwise healthy subjects.

Amoxicillin concentration in pus from abscess caused by odontogenic infection

1. Amoxicillin concentration in pus from odontogenic infection was assayed and the concentrations were compared with MIC (minimum inhibitory concentration) of alpha-hemolytic streptococci isolated from odontogenic infection. 2. Measurable amoxicillin concentrations in serum and pus were found in all instances (n = 16). 3. The mean peak concentrations in serum and pus were found at identical times, 1.5 hr after administration, which were 5.92 and 0.90 micrograms/ml, respectively. 4. The mean concentration ratio of pus/serum at the peak time was 0.15. 5. All amoxicillin concentrations in pus at the peak time exceeded the MIC for 90% of alpha-hemolytic streptococci (0.25 micrograms/ml).

Nonlinearities in amoxycillin pharmacokinetics. II. Absorption studies in the rat

Most factors influencing amoxycillin oral absorption are, even today, unknown. Since many dosage schedules have been shown to lead to incomplete absorption, it would be desirable to find a suitable animal model where these factors could be studied in depth. In this paper, it is shown that, in the rat, plasma level curves obtained after oral doses of 7 and 28 mg kg-1 are poorly fitted using first-order absorption kinetics and that the best fit is obtained through the use of an input equation combining zero and first-order kinetics. In contrast, plasma level curves found after intraduodenal administration of amoxycillin solutions (7 mg kg-1) are well fitted by first-order input kinetics. It would seem that precipitation of some dose fraction of the orally administered antibiotic may occur in proximal gastrointestinal areas; this plays an important role in absorption profiles and prevents any possible saturation phenomena associated with active intestinal transport of the antibiotic. A comparative study of available human oral data revealed close similarities with those found in rats. As a result, the plasma level curve fitting was greatly improved by the use of the input function described here for the rat. Although oral bioavailability (as assessed from urinary excretion data) is lower in this latter species, the use of suitable correction factors led to superimposable plasma level curves in the two species, as occurred in previously reported disposition studies.

Nonlinearities in amoxycillin pharmacokinetics. I. Disposition studies in the rat

Several features of amoxycillin pharmacokinetics in man are not well known in spite of the extensive clinical use of the antibiotic. In this paper it is demonstrated that amoxycillin disposition kinetics in rats is clearly nonlinear, and that this may be due mainly to its elimination mechanisms. At different intravenous bolus dose levels, and in steady-state perfusion studies, the most striking feature is an increased renal clearance as dose increases (from 3.5 to 7.0 mg kg-1 for intravenous bolus, and from 4.6 to 20.0 micrograms min-1 for intravenous perfusions). This phenomenon has been attributed to a saturation of the active renal tubular reabsorption of the antibiotic. When the intravenous dose is substantially increased (28.0 mg kg-1 bolus), plasma clearance tends to stabilize, probably because saturation of the active tubular secretion of amoxycillin takes place at these doses. Extrarenal clearance seems to remain linear throughout the entire dose range. On the basis of these observations and a review of selected bibliography, an interpretation of the kinetic disposition behaviour of amoxycillin in man is attempted.

Amoxicillin concentrations in serum, jaw cyst, and jawbone following a single oral administration

Forty-four patient who underwent enucleation of jaw cysts were administered amoxicillin preoperatively. Specimens of venous blood (44), walls and fluids from periodontal (31) and dentigerous (13) cysts, and jawbone (26) were obtained during the operation and assayed for amoxicillin content. Measurable concentrations were found in all specimens. The levels were higher in periodontal cysts than in dentigerous cysts, and higher in maxillary bone than in mandibular bone. Since amoxicillin can easily and rapidly pass through the epithelial lining according to the change in concentration, the penetration by amoxicillin of blood/cyst wall/cyst fluid probably depends on simple diffusion.

Comparison of amoxicillin and ampicillin activities in a continuous culture model of the human urinary bladder

Sixteen isolates of Escherichia coli were obtained from women with significant acute urinary tract infections who were subsequently treated with amoxicillin. The activities of amoxicillin and ampicillin against these organisms were compared in urine in a continuous culture apparatus which partly simulated the milieu of the human urinary bladder. After introduction of amoxicillin into the bladder model, mean viable counts for 14 susceptible strains (minimum inhibitory concentration less than or equal to 32 microgram/ml) at 10, 20, 30, and 45 min fell to 34, 8, 0.4, and 0.2% of the original. Corresponding figures for ampicillin were 56, 24, 11, and 2.4%. Viable counts obtained at seven timed intervals up to 2 h were significantly (P = 0.025) lower with amoxicillin than ampicillin. Both antibiotics had a similar activity in conventional disk susceptibility and surface plate minimum inhibitory concentration tests. The realism of the model was confirmed by comparing response to amoxicillin in vivo and in vitro. A serious discrepancy was seen in only one of the 16 cases.

Absorption and disposition kinetics of amoxicillin in normal human subjects

Pharmacokinetic parameters of amoxicillin were studied in healthy fasted subjects afqer both oral and intravenous administration of a single 500-mg dose. Serum levels and urinary excretion rates were determined at various time intervals by a microbiological method. The conventional two-compartment model with elimination occurring from the central compartment was used to analyze the data. Mean values were 3.40 h-1 for alpha and 0.68 h-1 for beta. Distribution constants kappa 12 and kappa 21 were 0.92 h-1 and 1.99 h-1, respectively. The rate constant for elimination from the central compartment, kappa 10, was 1.16 h-1. The volume of distribution was 20.2 liters (0.30 liter/kg), and the serum clearance was 13.3 liters/h. The absorption rate constant, kappa a, in the oral study, calculated by the Loo-Riegelman method, was 1.02 h-1, and the absorption half-life was 0.72 h. Absolute bioavailability after the oral dose was determined by comparing both the areas under the curve (AUC) and fractions of the antibiotic excreted unchanged in the urine. The AUC after oral administration was 77.4% of the intravenous AUC. On the other hand, recovery from the urine was 43.4% after the oral dose and 57.4% after the intravenous dose, indicating 76.5% bioavailability.

Pharmacokinetics of bacampicillin compared with those of ampicillin, pivampicillin, and amoxycillin

Bacampicillin, a new oral prodrug which in vivo is rapidly transformed to ampicillin, was compared with ampicillin, pivampicillin, and amoxycillin in a randomized cross-over study on 11 healthy volunteers. All drugs were given in oral doses equimolar to 400 mg of bacampicillin (800 mumol). The mean of the individual peak concentrations in serum was 8.3 mug/ml for bacampicillin, 7.1 mug/ml for pivampicillin, 7.7 mug/ml for amoxycillin, and 3.7 mug/ml for ampicillin. Furthermore, bacampicillin had a higher absorption rate than all the other drugs, although there were statistically significant differences only versus ampicillin. The peak serum levels of the individual subjects were more dispersed with ampicillin and amoxycillin, suggesting a more uniform absorption of bacampicillin and pivampicillin. The relative bioavailability of bacampicillin and pivampicillin was comparable, whereas ampicillin was only 2/3 that of the others.

Bioavailability of ampicillin and amoxicillin in fasted and nonfasted subjects

The influence of various test meals and fluid volume on the relative bioavailability of ampicillin and amoxicillin was studied in healthy human subjects. Serum amoxicillin levels were somewhat, but not always, significantly higher than those of ampicillin from equivalent oral doses. Food ingested immediately before dosing reduced serum levels and urinary excretion of both antibiotics to a similar extent. Reduction of dosed water volume caused a marked decrease in serum amoxicillin levels in fasted subjects.

Pharmacokinetics of amoxicillin: dose dependence after intravenous, oral, and intramuscular administration

Amoxicillin was studied in normal subjects after intravenous, oral, and intramuscular administration of 250-, 500-, and 1,000-mg doses. Serum drug levels were analyzed using a two-compartment open model, as well as area under the curve (AUC) and urinary recovery. The variations of these pharmacokinetic parameters were then examined using the three-way analysis of variance and linear regression equations. These results confirmed nearly complete oral absorption: AUC was 93% of intravenous absorption, and urinary recovery was 86%. The intramuscular administration of amoxicillin results in complete and reliable absorption with peak drug levels, AUCs, and urinary recovery equivalent to oral dosage. The absorption of lyophilized amoxicillin after intramuscular injection resulted in an AUC that was 92% of intravenous absorption and urinary recovery of 91%. The peak serum levels, time to peak, and other pharmacokinetic parameters for intramuscular injection were nearly identical to those for oral administration. Kinetics of both intramuscular and oral administration exhibited dose-dependent absorption (absorption rate constant, 1.3/h for 250 mg and 0.7/h for 1,000 mg). This resulted in relatively later and lower peak serum levels for increasing dose. Total absorption, however, showed no dose dependence, as indicated by urinary recovery and AUC, which changed by less than 10%.

Triple crossover study on absorption and excretion of ampicillin, talampicillin, and amoxycillin

Talampicillin and amoxycillin were shown to be absorbed twice as well as ampicillin in a triple crossover experiment.

Sequence effect on ampicillin blood levels noted in an amoxicillin, ampicillin, and epicillin triple crossover study

Amoxicillin, ampicillin, and epicillin (500 mg of each) were given orally to fasting men and women in a triple crossover study. Peak serum concentrations were significantly higher for amoxicillin than for ampicillin and significantly lowest for epicillin. The concentrations of antibiotics in serum were comparable in men and women. Total urine recovery was highest for amoxicillin (56.7%) and lowest for epicillin (27.5%), and higher in men than in women for each of the three antibiotics. Saliva, sweat, and tears contained only very small amounts of amoxicillin and, rarely, ampicillin or epicillin. A significant (P < 0.02) sequence effect was noted in that peak serum concentrations of ampicillin were higher (6.4 mug/ml) if epicillin had been taken the previous week than when ampicillin was taken first (2.7 mug/ml).

Oral amoxicillin in acute uncomplicated gonorrhea

Of 53 patients with acute uncomplicated gonorrhea treated with amoxicillin 2 g and probenecid 1 g orally as a single administration, six failed to return for follow-up examination, 10 developed postgonococcal urethritis and one was a treatment failure. The remainder achieved symptomatic cure in an average of 2.3 days. Adverse drug effects were infrequent, mild and transient. We conclude that this dose of amoxicillin and probenecid is a safe and effective treatment regimen.

Clinical and laboratory evaluation of amoxicillin (BRL 2333) in the treatment of urinary tract infections

Amoxicillin (alpha-amino-p-hydroxybenzyl penicillin) is a new oral semisynthetic penicillin with antibacterial activity similar to that of ampicillin; however, it is more completely absorbed and urinary concentrations are higher. Twenty-seven patients during 28 episodes of urinary tract infection were treated with oral amoxicillin given either as 250- or 500-mg doses. Clinical cure or improvement occurred in 23 of 27 infections (85%); eradication of the responsible organisms occurred in 23 of 26 infections (88%); and both clinical cure or improvement and eradication occurred in 20 of 25 infections (80%). Three infections relapsed. Failure to respond bacteriologically was associated with resistant organisms in two patients and with chronic pyelonephritis (Proteus mirabilis) is one. Concentrations of amoxicillin in serum obtained 2 h after administration were more variable than those previously reported for reasons which were obscure. In vitro studies revealed amoxicillin to be comparable to ampicillin when tested against most gram-negative bacilli; however, in this situation amoxicillin may be more effective than ampicillin against enterococci.