Validation of a Dried Blood Spot Ceftriaxone Assay in Papua New Guinean Children with Severe Bacterial Infections

Validated HPLC method for ceftriaxone from dried blood spots for pharmacokinetic studies and therapeutic drug monitoring in neonatal population

Background: Pharmacokinetic evaluation is essential for the precise dosing of ceftriaxone in neonates. There is a need for developing a sensitive, affordable and convenient analytical method that can estimate ceftriaxone from dried blood spot (DBS) samples of neonates. Method: An HPLC-UV method was developed and validated as per ICH M10 for ceftriaxone from DBS and plasma using an Inertsil-ODS-3V column with gradient elution. DBS samples were extracted with methanol. Clinical validation was performed using neonatal samples. Results: The developed plasma- and DBS-based-HPLC method were linear from 2-700 μg/ml and 2-500 μg/ml, respectively, for ceftriaxone. Bland-Altman analysis indicated a strong interconvertibility between the plasma and DBS assays. Conclusion: Observed concentrations in clinical samples were comparable to the predicted concentrations, proving the clinical validity of the method.

Population pharmacokinetic study of benzathine penicillin G administration in Indigenous children and young adults with rheumatic heart disease in the Northern Territory, Australia

BACKGROUND

Benzathine penicillin G (BPG) is the cornerstone of secondary prophylaxis to prevent Streptococcus pyogenes infections, which precede acute rheumatic fever (ARF). The paucity of pharmacokinetic (PK) data from children and adolescents from populations at the highest risk of ARF and rheumatic heart disease (RHD) poses a challenge for determining the optimal dosing and frequency of injections and undermines efforts to develop improved regimens.

METHODS

We conducted a 6 month longitudinal PK study of young people receiving BPG for secondary prophylaxis. Throat and skin swabs were collected for microbiological culture along with dried blood spot (DBS) samples for penicillin concentrations. DBSs were assayed using LC-MS/MS. Penicillin concentration datasets were analysed using non-linear mixed-effects modelling and simulations performed using published BMI-for-age and weight-for-age data.

RESULTS

Nineteen participants provided 75 throat swabs, 3 skin swabs and 216 penicillin samples. Throat cultures grew group C and G Streptococcus. Despite no participant maintaining penicillin concentration >20 ng/mL between doses, there were no S. pyogenes throat infections and no ARF. The median (range) observed durations >20 ng/mL for the low- and high-BMI groups were 14.5 (11.0-24.25) and 15.0 (7.5-18.25) days, respectively.

CONCLUSIONS

Few patients at highest risk of ARF/RHD receiving BPG for secondary prophylaxis maintain penicillin concentrations above the target of 20 ng/mL beyond 2 weeks during each monthly dosing interval. These PK data suggest that some high-risk individuals may get inadequate protection from every 4 week dosing. Future research should explore this gap in knowledge and PK differences between different populations to inform future dosing schedules.

Determination of ceftriaxone in human plasma using liquid chromatography-tandem mass spectrometry

Ceftriaxone is a cephalosporin antibiotic drug used as first-line treatment for a number of bacterial diseases. Ceftriaxone belongs to the third generation of cephalosporin and is available as an intramuscular or intravenous injection. Previously published pharmacokinetic studies have used high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for the quantification of ceftriaxone. This study aimed to develop and validate a bioanalytical method for the quantification of ceftriaxone in human plasma using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation of 100 µl plasma sample in combination with phospholipid-removal techniques to minimize matrix interferences. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C18 column with 10 mM ammonium formate containing 2% formic acid: acetonitrile as mobile phase at a flow rate of 0.4 ml/min with a total run time of 10 minutes. Both the analyte and cefotaxime (internal standard) were detected using the positive electrospray ionization (ESI) mode and selected reaction monitoring (SRM) for the precursor-product ion transitions m/z 555.0→396.1 for ceftriaxone and 456.0→324.0 for cefotaxime. The method was validated over the concentration range of 1.01-200 μg/ml. Calibration response showed good linearity (correlation coefficient > 0.99) and matrix effects were within the ±15% limit in 6 different lots of sodium heparin plasma tested. However, citrate phosphate dextrose plasma resulted in a clear matrix enhancement of 24% at the low concentration level, which was not compensated for by the internal standard. Different anticoagulants (EDTA, heparin and citrate phosphate dextrose) also showed differences in recovery. Thus, it is important to use the same anticoagulant in calibration curves and clinical samples for analysis. The intra-assay and inter-assay precision were less than 5% and 10%, respectively, and therefore well within standard regulatory acceptance criterion of ±15%.

Determination of ceftriaxone in human plasma using liquid chromatography–tandem mass spectrometry

Ceftriaxone is a cephalosporin antibiotic drug used as first-line treatment for a number of bacterial diseases. Ceftriaxone belongs to the third generation of antibiotics and is available as an intramuscular or intravenous injection. Previously published pharmacokinetic studies have used high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for the quantification of ceftriaxone. This study aimed to develop and validate a bioanalytical method for the quantification of ceftriaxone in human plasma using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation of 100 µl plasma sample in combination with phospholipid-removal techniques to minimize matrix interferences. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C18 column with 10 mM ammonium formate containing 2% formic acid: acetonitrile as mobile phase at a flow rate of 0.4 ml/min with a total run time of 10 minutes. Both the analyte and cefotaxime (internal standard) were quantified using the positive electrospray ionization (ESI) mode and selected reaction monitoring (SRM) for the precursor-product ion transitions m/z 555.0→396.1 for ceftriaxone and 456.0→324.0 for cefotaxime. The method was validated over the concentration range of 1.01-200 μg/ml. Calibration response showed good linearity (correlation coefficient > 0.99) and matrix effects were within the ±15% limit in 6 different lots of sodium heparin plasma tested. However, citrate phosphate dextrose plasma resulted in a clear matrix enhancement of 24% at the low concentration level, which was not compensated for by the internal standard. Different anticoagulants (EDTA, heparin and citrate phosphate dextrose) also showed differences in recovery. Thus, it is important to use the same anticoagulant in calibration curves and clinical samples for analysis. The intra-assay and inter-assay precision were less than 5% and 10%, respectively, and therefore well within standard regulatory acceptance criterion of ±15%.

Population Pharmacokinetic Study of Ceftriaxone in Elderly Patients, Using Cystatin C-Based Estimates of Renal Function To Account for Frailty

Ceftriaxone is widely used for respiratory and urinary infections in elderly and frail patients, but there are few pharmacokinetic studies. A prospective population pharmacokinetic study of ceftriaxone in adults over 65 years old was undertaken. Dried blood spots collected at baseline (predose) and 0.5, 1, 4, 8, and 24 h after administration of 1 g of ceftriaxone were assayed using a validated liquid chromatography-mass spectroscopy analytical method. Frailty was classified using the Edmonton frailty scale and grip strength via a hand dynamometer. Estimates of glomerular filtration rate were determined using creatinine-based and cystatin C-based equations. Of 26 patients recruited, 23 (88%) were vulnerable or very frail. Estimates of drug clearance improved significantly with a cystatin C-based estimate of renal function that accounted for frailty. Simulations indicate that the combined effects of ranges of size and renal function resulted in a 6-fold range in peak ceftriaxone concentrations and 9-fold range in total exposure (area under the concentration-time curve [AUC]). For elderly patients with moderate or severe renal impairment, 48-h dosing results in greater trough concentrations and total exposure than the trough concentrations and total exposure in patients with normal renal function receiving 24-h dosing. Cystatin C-based measures of renal function improved predictions of ceftriaxone clearance in elderly patients.

A population pharmacokinetic study of benzathine benzylpenicillin G administration in children and adolescents with rheumatic heart disease: new insights for improved secondary prophylaxis strategies

BACKGROUND

Benzathine benzylpenicillin G (BPG) is recommended as secondary prophylaxis to prevent recurrence of acute rheumatic fever and subsequent rheumatic heart disease (RHD). Following intramuscular injection, BPG is hydrolysed to benzylpenicillin. Little is known of the pharmacokinetics of benzylpenicillin following BPG in populations at risk of RHD.

METHODS

We conducted a longitudinal pharmacokinetic study of children and adolescents receiving secondary prophylaxis throughout six monthly cycles of BPG. Dried blood spot samples were assayed with LC-MS/MS. Benzylpenicillin concentrations were analysed using non-linear mixed-effects modelling with subsequent simulations based on published BMI-for-age and weight-for-age data.

RESULTS

Eighteen participants contributed 256 concentrations for analysis. None had benzylpenicillin concentrations >0.02 mg/L for the full time between doses. The median duration above this target was 9.8 days for those with a lower BMI (<25 kg/m2), who also had lower weights, and 0 days for those with a higher BMI (≥25 kg/m2). Although fat-free mass was a key determinant of benzylpenicillin exposure after a standard dose of BPG, having a higher BMI influenced absorption and almost doubled (increase of 86%) the observed t½.

CONCLUSIONS

Few children and adolescents receiving BPG as secondary prophylaxis will achieve concentrations >0.02 mg/L for the majority of the time between injections. The discordance of this observation with reported efficacy of BPG to prevent rheumatic fever implies a major knowledge gap relating to pharmacokinetic/pharmacodynamic relationships between benzylpenicillin exposure and clinical outcomes.

Determination of ceftriaxone in human plasma using liquid chromatography–tandem mass spectrometry

Ceftriaxone is a cephalosporin antibiotic drug used as first-line treatment for several bacterial diseases. Ceftriaxone belongs to the third generation of antibiotics and is available as an intramuscular or intravenous injection. Previously published pharmacokinetic studies have mainly used high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) for the quantification of ceftriaxone. This study aimed to develop and validate a bioanalytical method for the quantification of ceftriaxone in human plasma using liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Sample preparation was performed by protein precipitation in combination with phospholipid-removal techniques for cleaning up matrix interferences. The chromatographic separation was performed on an Agilent Zorbax Eclipse Plus C18 column with 10 mM ammonium formate containing 2% formic acid: acetonitrile as mobile phase at a flow rate of 0.4 ml/min. Both the analyte and cefotaxime (internal standard) were quantified using the positive electrospray ionization (ESI) mode and selected reaction monitoring (SRM) for the precursor-product ion transitions m/z 555.0→396.1 for ceftriaxone and 456.0→324.0 for cefotaxime. The method was validated over the concentration range of 1.01-200 μg/ml. Calibration response showed good linearity (correlation coefficient > 0.99) and no significant matrix effects were observed. The intra-assay and inter-assay precision were less than 5% and 10%, respectively, and therefore well within standard regulatory acceptance criterion of ±15%.