Real-World Comparative Effectiveness and Safety of Non-Vitamin K Antagonist Oral Anticoagulants vs. Warfarin in a Developing Country

We aimed to compare effectiveness and safety of the non-vitamin K antagonist oral anticoagulants (NOACs) vs. warfarin for stroke prevention in nonvalvular atrial fibrillation (NVAF) in a developing country where anticoagulation control with warfarin is suboptimal. A real-world study was conducted among patients with NVAF in Thailand receiving NOACs and warfarin from 9 hospitals during January 2012 to April 2018. Propensity-score weighting was used to balance covariates across study groups. Cox regression models were used to compare the risk of thromboembolism, major bleeding, and net adverse clinical events across matched cohorts. A total of 2,055 patients; 605, 604, 441, and 405 patients receiving warfarin, rivaroxaban, dabigatran, and apixaban, respectively, were included. Median (interquartile range) time in therapeutic range (TTR) for warfarin users was 49.5% (26.6%-70.3%). Compared with warfarin, NOACs were associated with a significant reduction in major bleeding either when analyzed as a group (adjusted hazard ratio (HR) (95% confidence interval (CI)) of 0.46 (0.34-0.62) or by each agent. Compared with warfarin users with poor TTR, apixaban (adjusted HR 0.48, 95% CI 0.26-0.86, P = 0.013) and dabigatran (adjusted HR 0.44, 95% CI 0.21-0.90, P = 0.025) were associated with a lower risk of thromboembolism, in addition to markedly lower risk of major bleeding. In a healthcare system where anticoagulation control with warfarin is suboptimal, use of NOACs was associated with a profound reduction in major bleeding. The effectiveness and safety advantages of NOACs were more pronounced compared with warfarin users with low TTR.

Knowledge of stroke and medication adherence among patients with recurrent stroke or transient ischemic attack in Indonesia: a multi-center, cross-sectional study

BackgroundThere is a limited data in Indonesia regarding the stroke knowledge and medication adherence among stroke survivors.ObjectiveTo assess the level of stroke knowledge and medication adherence along with their relationship among stroke survivors.SettingTwo tertiary-care hospitals in Surabaya, East Java, Indonesia.MethodsA prospective, cross-sectional study was conducted among 215 stroke survivors. Stroke Knowledge Test and the Morisky Green Levine Adherence Scale questionnaires were used to evaluate stroke knowledge and medication adherence, respectively. Binary logistic regression was performed to assess the rela tionship between stroke knowledge and medication adherence. Main outcome measuresRelationship between stroke knowledge and medication adherence.ResultsA total of 215 patients with mean age of 56.34 ± 8.69 years were recruited into this study. Mean Stroke Knowledge Test score was 7.89 ± 3.38 with 76.7% had low level of stroke knowledge. Mean Morisky Green Levine Adherence Scale was 3.05 ± 1.11 with 52.1% had low to medium medication adherence. Education and duration of stroke correlated with stroke knowledge level (Spearman's correlation coefficient: 0.307, p = 0.001 and 0.128, p = 0.041, respectively). Age and disability correlated with medication adherence (Spearman's correlation coefficient: 0.169; p = 0.013 and 0.171; p = 0.012), respectively. After adjustment for covariates, stroke knowledge level was independently associated with medication adherence (adjusted OR: 4.37, 95% CI 2.00-9.53; p < 0.001).ConclusionStroke knowledge was low among Indonesian stroke survivors and independently related to medication adherence. Attempts should be made to increase stroke knowledge which may improve medication adherence among stroke survivors.

Prescriber compliance to direct oral anticoagulant labels and impact on outcomes in Thailand

AIMS

This study aimed to evaluate the prescriber compliance to the approved labels of direct oral anticoagulants (DOACs) and impact of appropriateness of dosing on clinical outcomes.

METHODS

A retrospective study was conducted using simple-stratified random sampling of adult patients receiving ≥6 months of DOACs for various indications during 2013-2017 in 10 tertiary care hospitals. Patients were classified into 3 dosing groups including approved dose, underdosing and overdosing based on the Thai Food and Drug Administration-approved labels. Cox proportional hazard models were used to evaluate the impact of different dosings on thromboembolic and bleeding events.

RESULTS

From 1200 patients included in the data analysis, prescribing of DOACs was consistent with the approved indications in 1130 cases (94.2%) while 70 patients (5.8%) received DOACs despite having contraindications or with off-label usage. Among 1026 cases of dosing evaluation cohort, 688 patients (67.1%) received approved doses. There were 227 (21.9%) and 110 (10.7%) cases of underdosing and overdosing, respectively. Multivariate analysis showed that underdosing was associated with an increased risk of thromboembolism 3.023 (95% confidence interval [CI]: 1.291-7.080; P = .011) while overdosing was associated with an increased risk of bleeding requiring hospitalization (adjusted hazard ratio, 3.045; 95% CI, 1.501-6.178; P = .002) and Bleeding Academic Research Consortium type 2 or more (adjusted hazard ratio, 2.196; 95% CI, 1.083-4.452; P = .029).

CONCLUSION

Prescribers' compliance to approved indications were high. However, 1/3 of DOAC prescriptions were inconsistent with approved dosing. Dosing deviation was associated with an increase in adverse clinical outcomes.

Relationship of anemia and clinical outcome in heart failure patients with preserved versus reduced ejection fraction in a rural area of Thailand

Background

Heart failure (HF) has become a significant health burden in developing countries where anemia is highly prevalent. Limited data exists on the effects of anemia on HF in these population.

Methods

A retrospective observational study was conducted in all adult patients hospitalized due to HF at Buriram Hospital in Thailand, during July 2010 to June 2015. Survival analysis was performed to evaluate the impact of anemia on 1- year all-cause mortality for the overall cohort, patients with HF with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF).

Results

A total of 414 HF patients including 287 HFpEF patients (69.3%) and 127 HFrEF patients (30.7%) were included in our analysis. Mean age was 62.51 ± 14.89 years, with 55% female. Overall prevalence of anemia in HF was 62.6% (259 patients). One-year all-cause mortality was significantly higher in patients with anemia than in non-anemia groups (20.08% vs 12.26%, p = 0.041). When analyzed based on types of HF, anemia significantly increased mortality risk in HFpEF group [adjusted hazard ratio (HR) 2.667, 95%CI, 1.216–5.853, p = 0.014] but not with HFrEF group (adjusted HR 0.901, 95%CI, 0.376–2.155, p = 0.804). The mortality of anemic patients who were left untreated was significantly higher than those who were treated (adjusted HR 2.13, 95%CI, 1.13–3.99, p = 0.027).

Conclusion

Anemia significantly increased mortality in HF patients, especially among HFpEF. Attempts to identify, diagnose and manage anemia should be integrated in HF care plan in developing countries with high prevalence of anemia.

Genetic and clinical risk factors associated with phenytoin-induced cutaneous adverse drug reactions in Thai population

OBJECTIVE

This study aimed to describe the genetic and clinical risk factors associated with phenytoin-induced cutaneous adverse drug reactions (PHT-induced cADRs) in Thai patients.

METHOD

A retrospective case-control study was conducted among 88 PHT- cADRs (25 SJS/TEN, 37 DRESS/DIHS and 26 MPE) compared to 70 PHT-tolerant controls during 2008-2017. Genotyping was performed by Taqman RT-PCR (EPHX1 337 T > C, EPHX1 416A > G and CYP2C9*3), pyrosequencing (UGT1A1*28, UGT1A1*6) and polymerase chain reaction-sequence-specific oligonucleotide probe (HLA-B). Chi-squared test and binary logistic regression were used to identify factors associated with PHT-cADRs.

RESULTS

Multivariate analysis showed that HLA-B*46:01 was significantly associated with all PHT-induced cADRs (OR 2.341; 95% CI, 1.078-5.084; P = .032). Age of ≥60 years showed a significant association with PHT-induced SJS/TEN (OR 3.600; 95% CI, 1.214-10.672; P = .021). CYP2C9*3 was almost reaching statistically associated with an increased risk of PHT-induced SJS/TEN (OR 4.800; 95% CI, 0.960-23.990; P = .056). While HLA-B*56:02/04 was found to have a significant association with PHT-induced DRESS/DIHS (OR 29.312; 95% CI, 1.213-707.994; P = .038). Moreover, female gender and HLA-B*40:01 were associated with an increased risk of PHT-induced MPE at OR 5.734; 95% CI, 0.910-58.351; P = .042 and OR 3.647; 95% CI, 1.193-11.147; P = .023, respectively.

CONCLUSION

Both clinical (advanced age, female gender) and genetic factors (HLA-B*46:01, CYP2C9*3, HLA-B*56:02/04 and HLA-B*40:01) contributed to the risk of PHT-induced cADRs. Further studies with larger sample size may be warranted to confirm these findings and also the influence of EPHX1 gene.

Prognostic Value of Serum Procalcitonin level for the Diagnosis of Bacterial Infections in Critically-ill Patients

Background

Procalcitonin (PCT) is a diagnostic biomarker for bacterial infections in critically-ill patients. However, the cut-off value of PCT for the diagnosis of bacterial infections is unclear and unreliable. This study aimed to determine the optimal cut-off value of PCT for the diagnosis of bacterial infections in critically-ill patients.

Materials and Methods

We conducted a retrospective study involving 311 adult patients who had been admitted to the medical or surgical intensive care unit for more than 24 hours from 2013 to 2015. At least one blood test for PCT level was performed for all patients within the first 24 hours of suspecting an infection.

Results

One hundred and fifty-seven patients had bacterial infections, while 154 did not. Patients with bacterial infections had a significantly higher median PCT level than those without bacterial infections (1.90 ng/mL vs. 0.16 ng/mL, P <0.001). The area under the receiver operating characteristic curve of PCT for discriminating between bacterial and non-bacterial infections was 0.874 (95% confidence interval: 0.834, 0.914; P <0.001). The optimal cut-off value of PCT for differentiating between fevers due to bacterial infections from those due to non-bacterial infections was 0.5 ng/mL, with a sensitivity of 84.7%, specificity of 79.9%, positive predictive value of 81.1%, and negative predictive value of 83.7%.

Conclusion

PCT was found to be an accurate biomarker for the diagnosis of bacterial infections among patients admitted to medical and surgical intensive care units. The optimal cut-off value of PCT for the diagnosis of bacterial infections was 0.5 ng/mL.

Population pharmacokinetics of vancomycin in Thai patients

Population pharmacokinetics of vancomycin in Thai adult patients was determined by non-linear mixed-effects approach using 319 vancomycin serum concentrations from 212 patients. The data were best fitted by a two-compartment model and it was used to examine the effect of patient characteristics on the vancomycin pharmacokinetics. In the final model, there was a linear relationship between vancomycin clearance, CL (L/h), and creatinine clearance calculated by Cockcroft-Gault equation, CL_Cr (mL/min): CL  =0.044  ×  CL_Cr. Meanwhile, volume of central compartment, V₁ (L), was linearly related with the age (years old): V₁ = 0.542  × Age. Intercompartment clearance (Q) and volume of peripheral compartment (V₂) was 6.95 L/h and 44.2 L, respectively. The interindividual variability for CL, V₁, Q, and V₂ was 35.78, 20.93, 39.50, and 57.27%, respectively. Whereas, the intraindividual variability was 4.51 mg/L. Final model then was applied to predict serum vancomycin concentrations on validation group. Predictive performance revealed a bias of −1.43 mg/L (95% CI: −5.82–2.99) and a precision of 12.2 mg/L (95% CI: −1.60–26.16). In conclusion, population pharmacokinetic of vancomycin in Thai adult patients was developed. The model could be used to create vancomycin dosage regimen in the type of patient similar with the present study.

Pharmacokinetics and clinical application of intravenous valproate in Thai epileptic children

Roles of intravenous administration of valproate in status epilepticus and serial seizures are documented in adults and children. Pharmacokinetic parameters are necessary to predict the optimum therapeutic level after administration. A cross-sectional study to determine the pharmacokinetic parameters and safety of intravenous valproate for future application was conducted in Thai children from January to December 2008. There were eleven children, age-range 1-15 years (mean age 9.5 years) enrolled. Valproate of 15-20 mg/kg was administrated intravenously at the rate of 3 mg/kg/min, followed by 6 mg/kg every 6 h. Valproate level was determined prior to the initial dose and at ½, 1, 2, 4, 5, and 6 h postdose. Complete blood count, serum ammonia, and liver function tests were collected prior to the initial dose and at 6 h. Median loading dose was 19 mg/kg (range 15-20.5 mg/kg). Median maximum concentration at 30 min after infusion was 98.8 mcg/mL (range 67-161 mcg/mL). Median volume of distribution was 0.20 L/kg (range 0.15-0.53 L/kg). Median half-life was 9.5 h (range 4.4-24.2 h). Median clearance was 0.02 L/h/kg (range 0.01-0.05 L/h/kg). Six hours after initial dose, eight children did not have recurrent seizure. One child had brief seizure at 20 min after initial dose. Seizure recurred in two children at 4th and 5th hour. Asymptomatic transient elevation of serum ammonia was observed in two children. Volume of distribution of 0.20 L/kg could be applied for initial intravenous administration with a favorable efficacy.

Formulation development of morphine sulfate sustained-release tablets and its bioequivalence study in healthy Thai volunteers

The objectives of this study were to develop morphine sulfate sustained-release tablet formulations and to evaluate the bioequivalence compared with a commercial brand. The physicochemical properties of the formulated and commercial tablets were determined and compared. The bioequivalence investigation was carried out in 15 healthy male volunteers who received a single dose in a randomized two-way crossover design. After dosing, serial blood samples were collected for a period of 24 h. Morphine concentration was assayed by high-performance liquid chromatography with electrochemical detector. The log-transformed C(max) and AUC(s) were statistically compared by analysis of variance, and the 90% confidence intervals (CIs) of the ratio of the log-transformed C(max) and AUC(s) between the most promising developed formulation and the commercial product were determined. It was found that the dissolution rate profile of a developed formulation was similar to the commercial brand. Their similarity and difference factors were well within limits. In the bioequivalence study, the AUC(last) and AUC(inf) between the test and the reference products were not statistically different (p = 0.227 and p = 0.468, respectively), with the 90% CIs of 83.4-102.6% and 87.7-139.4%, respectively. However, the C(max) of the two formulations was significantly different (p = 0.019). The 90% CI of the developed formulation was 72.0-93.0% compared to the commercial product. In vitro dissolution of locally prepared morphine sulfate sustained-release tablets was comparable to commercial brand. However, the results justified the conclusion of lack of bioequivalence of the developed product to the commercial one.

Pharmacokinetics of ofloxacin in drug-resistant tuberculosis

The pharmacokinetics of ofloxacin were investigated in 11 drug-resistant pulmonary tuberculosis (TB) patients with a mean age (SD) of 38.09 (11.97) years. All patients received ofloxacin 10 mg/kg once daily combined with other active anti-TB drugs. Following an 8-h overnight fast, serum samples were drawn prior to and from 0.25 up to 24 hours after dosing. Serum ofloxacin concentrations were determined by high performance liquid chromatography (HPLC) assay. Pharmacokinetics of ofloxacin were well described by a linear, 2-compartment open model with first-order absorption and first-order elimination. Mean +/- SD of Cmax was 9.61 +/- 2.17 microg/ml occurred at 1.68 +/- 1.21 hours. Means +/- SD of AUC(0-24) and AUC(0-infinity) were 70.57 +/- 26.40 and 82.45 +/- 43.64 microg x h/ml, respectively. Ofloxacin distributed widely with a mean +/- SD of Vss/F of 1.37 +/- 0.24 L/kg. Mean +/- SD of CL/F was 8.19 +/- 2.53 L/h, whereas mean +/- SD of T(1/2beta) and mean residence time were 8.03 +/- 3.37 and 10.77 +/- 4.55 hours, respectively. The free Cmax/MIC of Mycobacterium tuberculosis of 7.7-15.4:1 was estimated. These suggested that ofloxacin 10 mg/kg once daily combined with other active anti-TB drugs provides sufficient Cmax/MIC ratio and long T(1/2beta) which supported its use in drug-resistant TB.

Intrapulmonary pharmacokinetics of ofloxacin in drug-resistant tuberculosis

OBJECTIVE

To determine the lung epithelial lining fluid (ELF) and serum levels of ofloxacin in drug-resistant tuberculosis patients during treatment.

DESIGN

Ten drug-resistant tuberculosis patients treated with ofloxacin containing regimens for at least 2 weeks were enrolled in the study. Subjects ingested ofloxacin 10 mg/kg and other anti-tuberculosis agents after overnight fasting.

RESULTS

Serum and bronchoalveolar lavage fluid were collected at 4 hours after treatment and assayed by high performance liquid chromatography. The mean concentrations of ofloxacin in serum and ELF were 5.889 +/- 1.096 and 16.583 +/- 8.697 mg/L, respectively. The mean ratio of ELF-to-serum ofloxacin concentration was 2.825 +/- 1.275.

CONCLUSION

Ofloxacin can penetrate well into the intra-alveolar fluid of patients treated for drug-resistant tuberculosis. The lung ELF concentrations were consistently higher than the minimal inhibitory concentrations of Mycobacterium tuberculosis as determined in vitro.

Pharmacokinetics of levofloxacin in healthy Thai male volunteers

The pharmacokinetics of levofloxacin, a new fluoroquinolone, were investigated in 12 healthy Thai male volunteers with an average age (SD) of 22.92 (2.50) years. A single oral dose of 300 mg or 500 mg levofloxacin was given to subjects following an 8- hour overnight fast. The drug was given in a controlled, randomized, 2 x 2 crossover design with a 1 week washout period. Venous blood samples were drawn prior to and from 0.25 up to 48 hours after dosing. Plasma levofloxacin concentrations were determined by HPLC assay. The pharmacokinetics of levofloxacin were well described by a linear, 2-compartment open model with first-order absorption with lag time and first-order elimination. Mean +/- SEM of Cmax after 300 mg and 500 mg dose was 4.83 +/- 0.33 and 7.75 +/- 0.71 micrograms/mL, respectively. Tmax ranged from 0.7 to 0.8 hours for both doses. Mean +/- SEM of AUC0-infinity was 35.77 +/- 2.06 micrograms x h/mL for 300 mg dose and 61.57 +/- 2.84 micrograms x h/mL for 500 mg dose. High distribution with VSS/F value of approximately 1.5 L/kg was demonstrated after both doses. Mean +/- SEM of CL/F value was 8.64 +/- 0.41 L/h and 8.31 +/- 0.37 L/h for a 300-mg and a 500-mg dose, respectively. Long t1/2 beta of 7 to 8 hours with the mean residence time of 10.43 +/- 0.43 hours and 10.49 +/- 0.38 hours after 300 mg and 500 mg dose, respectively, was observed. The results suggested that an oral 300 mg dose once daily provides sufficient Cmax to cover most Gram-negative and atypical bacteria (median MIC90 0.032-0.5 microgram/mL) common in mild to moderate respiratory tract infections or complicated urinary tract infections and Gram-positive bacteria (median MIC90 0.5 microgram/mL) common in skin and soft tissue infections. For severe cases or Streptococcus pneumoniae (MIC90 2 micrograms/mL) infection, a 500-mg dose should be recommended.

The period prevalence of catamenial epilepsy at Prasat Neurological Institute, Bangkok

The study was performed to assess the period prevalence of catamenial epilepsy in Thai female epileptic patients. Such a condition is defined as seizures related to menstruation which occur for at least 2 consecutive months within 1 patient during 4 days prior to and/or 6 days after the onset of menstruation. Patients with regular menstruation aged between 15-50 years attending the Out-Patient Department of Prasat Neurological Institute in Bangkok from 1 November, 1995 to 31 January, 1996 were recruited. Patients and/or their relatives were interviewed directly or by telephone using a questionnaire concerning menstrual history, seizures related to menstruation and they were requested to record these data for 2 further consecutive months. In cases where the interview could not be directly performed, a mailed questionnaire was used instead. All information was considered together with information reviewed from the OPD cards. Forty-six from 467 epileptic patients were considered to have catamenial epilepsy. The period prevalence thus was 98.5 in 1,000 women at risk and the mode of frequency of seizure occurrence was 2 days before menstruation. Generalized seizure was found more common in these patients than partial seizure. In particular, general tonic-clonic seizure and complex partial seizure were the most common for each type, respectively. About 70 per cent of the patients used more than 1 anti-convulsant drugs to control their seizures. Some have received other drug supplements to relieve seizure exacerbation but only mild improvement was observed. No change in body weights measured in 2 or 1 day before menstruation, on the first menstrual day and in 1 day after menstruation was demonstrated in all patients. The results suggest that catamenial epilepsy is one of the clinically significant problems of seizure control in Thai female epileptic patients and multifactors may be involved in this condition.

Bioavailability of phenytoin sodium capsules available in Thailand. Part II: In vivo study

Four phenytoin brands, dilantin and three local brands (brand A, B and C) were selected for the bioavailability study. The study was carried out in 16 healthy male Thai volunteers with the average age of 21 years old. A single oral dose of 300 mg (three capsules of 100-mg) phenytoin sodium was given to subjects following an 8 hour-overnight fast. The tested drugs were given in a single-blind randomized crossover with at least 2 weeks of washout period. Venous blood samples of approximately 5 ml were drawn before medication and at 1, 2, 4, 6, 8, 10, 12, 24, 48 and 72 hours post dosing. Plasma phenytoin concentrations were determined by HPLC assay. The pharmacokinetic parameters were calculated from the plasma-concentration time curve of an innovator brand, dilantin, by PCNONLIN program. Elimination rate constant and half-life were 0.2 h-1 and 19 h, respectively. The maximum concentration (Cmax) and time to peak (Tmax) were 1.98 micrograms/ml and 9.6 h, respectively. Bioavailability study was determined by comparing the area under the plasma concentration time curve (AUC), maximum plasma concentration (Cmax) and time to reach maximum plasma concentration (Tmax) by using ANOVA. The result indicated that two local brands (brand A and brand C) were not bioequivalent to the innovator in terms of Cmax and AUC0-alpha, whereas Tmax was not significantly different among these 4 brands. Cmax and AUC of brand A and C were significantly higher than the innovator brand. In addition, the plasma concentration time profile of brand C was also different from other brands with the steep peak which yielded a Cmax value double that of the Cmax of the innovator. However, brand B (from Research and Development Institute, Government Pharmaceutical Organization) was bioequivalent to dilantin after 4 times of product formulation adjustment. This present study demonstrated that the local products (brand A and brand C) were not bioequivalent with the innovator. Thus, the interchange from one brand to another must be performed cautiously or should be avoided, otherwise phenytoin blood levels should be monitored closely together with the clinical signs and symptoms of the patients.

Determination of dose-dependent absorption of amoxycillin from urinary excretion data in healthy subjects

Measurement of unchanged drug in urine was used to study the rate and extent of amoxycillin absorption after administration of amoxycillin sodium solution to six healthy subjects in a Latin-Square crossover design. The mean (95% CI) fraction of the dose excreted as unchanged amoxycillin decreased (P < 0.05) from 0.50 (0.44-0.56) after 97 mg amoxycillin sodium (= 0.25 mmol amoxycillin) to 0.23 (0.19-0.27) after 3103 mg (8 mmol), while the mean residence time determined from urinary excretion rate data increased (P < 0.05) from 1.54 (1.32-1.76) h to 2.16 (2.01-2.41) h. Plots of total urinary excretion and initial (0-30 min) excretion of unchanged drug vs dose indicated significant non-linearity above 776 mg doses. Michaelis-Menten parameters describing this relationship with respect to amount absorbed were 3.02 mmol for maximum amount absorbed and 1.93 mmol for amount absorbed at half maximum for 0-30 min. These results support a saturable absorption mechanism for amoxycillin which had clinical implications for high oral amoxycillin doses, and for competition with other drugs having capacity-limited absorption.

Simple analysis of amoxycillin in plasma by high performance liquid chromatography with internal standardization and ultraviolet detection

A simple high performance liquid chromatographic method with ultraviolet detection at 229 nm is described for quantitation of amoxycillin in plasma. After deproteination of plasma samples with perchloric acid and adjustment of the pH to 4.9, the supernatant was injected onto a reversed phase C18 column, using acetonitrile:phosphate buffer (0.01 M, pH 7.4) (1:25 v/v) as the mobile phase. Amoxycillin and the internal standard, cefadroxil, were eluted at 23 min and 12 min, respectively, without interference from endogenous substances. Processed samples were stable for at least 24 h at room temperature which permitted automated batch processing overnight. Calibration plots of the amoxycillin to cefadroxil peak-height ratio vs. amoxycillin concentration were linear (P < 0.0001; r > or = 0.995) from 0.25 mg/L to at least 16.0 mg/L. Between-day and within-day imprecision (CV) ranged between 3.7% and 17.7%. Absolute recovery for amoxycillin and cefadroxil exceeded 82%. The application was demonstrated by the analysis of amoxycillin in human plasma after a single oral dose of amoxycillin (250 mg) suspension.

High-performance liquid chromatographic determination of amoxicillin in urine using solid-phase, ion-pair extraction and ultraviolet detection

A simple, robust high-performance liquid chromatographic method is described for assaying amoxicillin in urine. Sample clean-up involved solid-phase, ion-pair extraction onto Sep-Pak C18 cartridges followed by elution with acetonitrile (3%, v/v) in pH 4.85 buffer. Separations were performed on an Ultrasphere C18 column with a mobile phase comprising acetonitrile (32.5 ml) and pH 7.1 phosphate buffer (0.01 M, 1000 ml). Peaks were detected at 229 nm. Recovery was greater than 94%. Plots of peak area against urinary amoxicillin concentration were linear (r > 0.999) from 5 to 500 mg/l. Between-day and within-day imprecision (coefficient of variation) ranged between 3.0 and 15.5%. Inaccuracy was 7.1%, or less.