The effects of bivalent human papillomavirus (HPV) vaccination on high-risk anogenital HPV infection among sexually active female adolescents with and without perinatally acquired HIV

BACKGROUND

Females with perinatal HIV (PHIV) infection are at elevated risk for anogenital high-risk human papillomavirus (HR-HPV) infection. Limited data are available around the effect of the HPV vaccination after initiation of sexual activity among PHIV youth. This study aims to assess the impact of a bivalent HPV vaccination on the persistence of anogenital HR-HPV among sexually active female PHIV youth and matched HIV-negative controls aged 12-24years in Thailand and Vietnam.

METHODS

During a 3-year study, prevalent, incident, and persistent HR-HPV infection were assessed at annual visits. A subset of participants received a bivalent HPV vaccine. Samples were taken for HPV testing from the vagina, cervix, and anus. HR-HPV persistence was defined as the detection of the same genotype(s) at any anogenital compartment over≥two consecutive visits.

RESULTS

Of the 93 PHIV and 99 HIV-negative female youth enrolled in this study, 25 (27%) PHIV and 22 (22%) HIV-negative youth received a HPV vaccine. Persistent infection with any HR-HPV type was significantly lower among PHIV youth who received the vaccine compared to those who did not (33%vs 61%, P =0.02); a difference was not observed among HIV-negative youth (35%vs 50%, P =0.82). PHIV infection (adjusted prevalence ratio [aPR] 2.31, 95% CI 1.45-3.67) and not receiving a HPV vaccine (aPR, 1.19, 95%CI 1.06-1.33) were associated with persistent anogenital HR-HPV infection.

CONCLUSIONS

Bivalent HPV vaccination after initiation of sexual activity was associated with reduced persistence of anogenital HR-HPV infection in Southeast Asian PHIV female youth, which may be related to vaccine cross-protection. Primary and catch-up HPV vaccinations should be prioritised for children and youth with HIV.

Factors Associated with Morbidity and Mortality Among Sexually Active Asian Adolescents and Young Adults with Perinatally Acquired HIV

We assessed morbidity and mortality among Thai and Vietnamese adolescents and young adults with perinatally acquired human immunodeficiency virus (PHIV) compared with matched HIV-negative peers, 12-24 years of age. Data on serious adverse events (SAEs) were prospectively collected between 2013 and 2018 according to U.S. NIH Division of AIDS criteria. Of 288 youth, 142 had PHIV and 146 were HIV negative. At enrollment, the overall median age was 19 (interquartile range [IQR] 17-20) years, 67% were female, and 95% were Thai. Almost all PHIV youth (99%) were receiving antiretroviral therapy; 50% self-reported adherence ≥95%. Median CD4 was 579 (IQR 404-800) cells/mm³, and 24% had HIV-RNA ≥1,000 copies/mL. During follow-up, 31 (22%) PHIV youth and 9 (6%) HIV-negative youth had at least one SAE. The overall crude SAE rate was 4.66 (3.42-6.35) per 100 person-years (PY); 7.22 (5.08-10.26) per 100 PY among youth with PHIV and 2.10 (1.09-4.03) per 100 PY in HIV-negative youth (p < .001). All seven deaths that occurred were among those with PHIV and primarily due to opportunistic infections (e.g., pneumocystis pneumonia, tuberculous meningitis). In multivariate analyses, having PHIV, being <20 years of age, and having anogenital high-risk human papillomavirus (HPV) infection with types 16 and/or 18 increased risk of SAEs. Among PHIV youth, CD4 count <350 cells/mm³, HIV-RNA ≥1,000 copies/mL, advanced WHO stages, and having anogenital HPV 16 and/or 18 infection predicted higher incidence of SAEs; no prior use of alcohol was protective. These data emphasize the need for tailored interventions for adolescents with PHIV to prevent long-term morbidity and mortality.

Incidence and Persistence of High-risk Anogenital Human Papillomavirus Infection Among Female Youth With and Without Perinatally Acquired Human Immunodefiency Virus Infection: A 3-year Observational Cohort Study

BACKGROUND

Female youth with perinatally acquired human immunodeficiency virus (PHIV) may be at higher risk than uninfected youth for persistent anogenital human papillomavirus (HPV) infection, due to prolonged immunodeficiency.

METHODS

A 3-year cohort study was conducted between 2013 and 2017 among Thai and Vietnamese PHIV and HIV-uninfected females 12-24 years, matched by age group and number of lifetime sexual partners. For HPV genotyping, cervical and anal samples were obtained at baseline and annually. Vaginal samples were collected at baseline and every 6 months. Factors associated with high-risk HPV (HR-HPV) persistence and incidence were assessed.

RESULTS

We enrolled 93 PHIV and 99 HIV-uninfected females. Median age was 19 (interquartile range [IQR] 18-20) years. For the 7 HR-HPV types (16, 18, 31, 33, 45, 52, 58) in the nonavalent HPV vaccine, PHIV had significantly higher incidence (P = .03) and persistence (P = .01) than HIV-uninfected youth over a 3-year period. Having HIV (adjusted hazard ratio [aHR] 2.1, 95% confidence interval [CI] 1.1-3.9) and ever using illegal substances (aHR 4.8, 95% CI 1.8-13.0) were associated with incident 7 HR-HPV infections. HIV-positive status (adjusted prevalence ratio [aPR] 2.2, 95% CI 1.5-3.2), recent alcohol use (aPR 1.75, 95% CI 1.2-2.5), and higher number of lifetime partners (aPR 2.0, 95% CI 1.4-3.1, for 3-5 partners; aPR 1.93, 95% CI 1.2-3.2, for ≥6 partners) were significantly associated with persistent 7 HR-HPV infections.

CONCLUSIONS

Female PHIV were at higher risk of having anogenital HR-HPV acquisition and persistence. Primary and secondary prevention programs for HPV infection and HPV-related diseases should be prioritized for PHIV children and youth.

Determinants of Viral Resuppression or Persistent Virologic Failure After Initial Failure With Second-Line Antiretroviral Treatment Among Asian Children and Adolescents With HIV

Of 56 children with perinatally acquired human immunodeficiency virus (HIV) who had been prescribed second-line protease inhibitor-based antiretroviral therapy and had ≥1 previous episode of viral failure (HIV RNA, ≥1000 copies/mL), 46% had ≥1, 34% had ≥2, and 23% had ≥3 consecutive episodes of viral failure during the 2 years of follow-up. Two of these children experienced a major protease inhibitor mutation.

Peritransition Outcomes of Southeast Asian Adolescents and Young Adults With HIV Transferring From Pediatric to Adult Care

PURPOSE

The aim of this article was to study the clinical and social outcomes of health care transition among Asian adolescents and young adults with HIV (AYHIV).

METHODS

AYHIV who transferred from a pediatric to an adult clinic within the past year across five sites in Malaysia, Thailand, and Vietnam had clinical and laboratory evaluations and completed questionnaires about their health, socioeconomic factors, and transition experiences. Multiple logistic regression was used to assess associations with HIV viremia.

RESULTS

Of 93 AYHIV enrolled between June 2016 and April 2017, 56% were female, 87% acquired HIV through perinatal exposure, median age was 20 years (interquartile range [IQR] 18.5-21). Two-thirds were in a formal education program, 43% were employed, 43% of females and 35% of males were sexually active. Median lifetime antiretroviral therapy duration was 6.2 years (IQR 3.3-10.7); 45% had received second-line therapy. Median CD4 was 601 cells/mm³ (IQR 477-800); 82% had HIV-RNA <40 copies/mL. Being in a relationship, a shorter posttransition duration, self-reported adherence of ≥95%, and higher CD4 were inversely associated with HIV viremia. Half felt very prepared for the transfer to adult care, and 20% frequently and 43% sometimes still met with pediatric providers. Two-thirds reported needing to keep their HIV a secret, and 23%-38% reported never or rarely having someone to discuss problems with.

CONCLUSIONS

Asian AYHIV in our cohort were concerned about the negative social impact of having and disclosing HIV, and one-third lacked people they could trust with their personal problems, which could have negative implications for their ability to navigate adult life.

Risk Factors for Human Papillomavirus Infection and Abnormal Cervical Cytology Among Perinatally Human Immunodeficiency Virus-Infected and Uninfected Asian Youth

Background

Infection with high-risk human papillomavirus (HR-HPV) may be higher in perinatally human immunodeficiency virus (HIV)-infected (PHIV) than HIV-uninfected (HU) adolescents because of long-standing immune deficiency.

Methods

PHIV and HU females aged 12-24 years in Thailand and Vietnam were matched by age group and lifetime sexual partners. At enrollment, blood, cervical, vaginal, anal, and oral samples were obtained for HPV-related testing. The Wilcoxon and Fisher exact tests were used for univariate and logistic regression for multivariate analyses.

Results

Ninety-three PHIV and 99 HU adolescents (median age 19 [18-20] years) were enrolled (June 2013-July 2015). Among PHIV, 94% were currently receiving antiretroviral therapy, median CD4 count was 593 (392-808) cells/mm3, and 62% had a viral load <40 copies/mL. Across anogenital compartments, PHIV had higher rates of any HPV detected (80% vs 60%; P = .003) and any HR-HPV (60% vs 43%, P = .02). Higher proportions of PHIV had abnormal Pap smears (eg, atypical squamous cells of unknown significance [ASC-US], 12% vs 14%; low-grade squamous intraepithelial neoplastic lesions, 19% vs 1%). After adjusting for ever being pregnant and asymptomatic sexually transmitted infections (STI) at enrollment, PHIV were more likely to have HR-HPV than HU (odds ratio, 2.02; 95% confidence interval, 1.09-3.77; P = .03).

Conclusions

Perinatal HIV infection was associated with a higher risk of HR-HPV and abnormal cervical cytology. Our results underscore the need for HPV vaccination for PHIV adolescents and for prevention and screening programs for HPV and other STIs.

Using Lopinavir Concentrations in Hair Samples to Assess Treatment Outcomes on Second-Line Regimens Among Asian Children

We conducted a prospective monitoring study to determine whether antiretroviral (ARV) levels in hair of Asian children on second-line protease inhibitor-based ARV therapy (ART) are associated with virologic failure (VF), compared to plasma drug levels and self-reported adherence. HIV-infected Asian children on second-line ART regimens were enrolled into a longitudinal cohort. Traditional adherence measures, plasma, and hair samples were collected 24 weeks after study enrollment. Hair ARV levels were determined via liquid chromatography/tandem mass spectrometry. Among 149 children on lopinavir/ritonavir-based regimens, 47% were female; the median [interquartile range (IQR)] age was 10.3 (7.9-13.3) years. The median CD4% was 26% (IQR 21.7-32.1%) and the median CD4 cell count 754 (IQR 596-1,013) cells/mm(3). The median duration of lopinavir-based ART prior to week 24 of the study was 2.9 (IQR 1.6-4.2) years. Adherence was >95% in 91% (135/148) by visual analogue scale and 89% (129/145) by pill count. The median lopinavir hair concentrations were 5.43 (IQR 3.21-9.01) ng/mg in children with HIV RNA >1,000 copies/ml and 9.96 (IQR 6.51-12.31) ng/mg in children with HIV RNA <1,000 copies/ml (p = 0.003). Plasma trough and lopinavir hair concentrations were not statistically significantly correlated (Pearson's correlation coefficient 0.20; p = 0.13). Increasing lopinavir hair concentrations in quartiles were strongly associated with virologic success (odds ratios ≥4.0, overall p = 0.02), while self-reported adherence, pill count, and plasma lopinavir levels were not. Based on this first report of hair ARV concentrations and virologic outcomes in children, ARV hair concentrations, representing longer-term adherence, may be useful to identify children at risk for VF.

Transmitted drug resistance in recently infected HIV-positive Individuals from four urban locations across Asia (2007-2010) - TASER-S

BACKGROUND

The availability of HIV antiretroviral therapy (ART) has been associated with the development of transmitted drug resistance-associated mutations (TDRM). TDRM can compromise treatment effectiveness in patients initiating ART and the prevalence can vary in different clinical settings. In this study, we investigated the proportion of TDRM in treatment-naïve, recently infected HIV-positive individuals sampled from four urban locations across Asia between 2007-2010.

METHODS

Patients enrolled in the TREAT Asia Studies to Evaluate Resistance - Surveillance Study (TASER-S) were genotyped prior to ART initiation, with resulting resistance mutations analysed according to the WHO 2009 list.

RESULTS

Proportions of TDRM from recently infected individuals from TASER-S ranged from 0% to 8.7% - Hong Kong: 3/88 (3.4%, 95% CI (0.71%-9.64%)); Thailand: Bangkok: 13/277 (4.7%, 95% CI (2.5%-7.9%)), Chiang Mai: 0/17 (0%, 97.5% CI (0%-19.5%)); and the Philippines: 6/69 (8.7%, 95% CI (3.3%-18.0%)). There was no significant increase in TDRM over time across all four clinical settings.

CONCLUSIONS

The observed proportion of TDRM in TASER-S patients from Hong Kong, Thailand and the Philippines was low to moderate during the study period. Regular monitoring of TDRM should be encouraged, especially with the scale-up of ART at higher CD4 levels.

Capacity building and predictors of success for HIV-1 drug resistance testing in the Asia-Pacific region and Africa

BACKGROUND

The TREAT Asia Quality Assessment Scheme (TAQAS) was developed as a quality assessment programme through expert education and training, for laboratories in the Asia-Pacific and Africa that perform HIV drug-resistance (HIVDR) genotyping. We evaluated the programme performance and factors associated with high-quality HIVDR genotyping.

METHODS

Laboratories used their standard protocols to test panels of human immunodeficiency virus (HIV)-positive plasma samples or electropherograms. Protocols were documented and performance was evaluated according to a newly developed scoring system, agreement with panel-specific consensus sequence, and detection of drug-resistance mutations (DRMs) and mixtures of wild-type and resistant virus (mixtures). High-quality performance was defined as detection of ≥95% DRMs.

RESULTS

Over 4.5 years, 23 participating laboratories in 13 countries tested 45 samples (30 HIV-1 subtype B; 15 non-B subtypes) in nine panels. Median detection of DRMs was 88-98% in plasma panels and 90-97% in electropherogram panels. Laboratories were supported to amend and improve their test outcomes as appropriate. Three laboratories that detected <80% DRMs in early panels demonstrated subsequent improvement. Sample complexity factors - number of DRMs (p<0.001) and number of DRMs as mixtures (p<0.001); and laboratory performance factors - detection of mixtures (p<0.001) and agreement with consensus sequence (p<0.001), were associated with high performance; sample format (plasma or electropherogram), subtype and genotyping protocol were not.

CONCLUSION

High-quality HIVDR genotyping was achieved in the TAQAS collaborative laboratory network. Sample complexity and detection of mixtures were associated with performance quality. Laboratories conducting HIVDR genotyping are encouraged to participate in quality assessment programmes.

Comparison of predicted susceptibility between genotype and virtual phenotype HIV drug resistance interpretation systems among treatment-naive HIV-infected patients in Asia: TASER-M cohort analysis

Background

Accurate interpretation of HIV drug resistance (HIVDR) testing is challenging, yet important for patient care. We compared genotyping interpretation, based on the Stanford University HIV Drug Resistance Database (Stanford HIVdb), and virtual phenotyping, based on the Janssen Diagnostics BVBA’s vircoTYPE™ HIV-1, and investigated their level of agreement in antiretroviral (ARV) naive patients in Asia, where non-B subtypes predominate.

Methods

Sequences from 1301 ARV-naive patients enrolled in the TREAT Asia Studies to Evaluate Resistance – Monitoring Study (TASER-M) were analysed by both interpreting systems. Interpretations from both Stanford HIVdb and vircoTYPE™ HIV-1 were initially grouped into 2 levels: susceptible and non-susceptible. Discrepancy was defined as a discordant result between the susceptible and non-susceptible interpretations from the two systems for the same ARV. Further analysis was performed when interpretations from both systems were categorised into 3 levels: susceptible, intermediate and resistant; whereby discrepancies could be categorised as major discrepancies and minor discrepancies. Major discrepancy was defined as having a susceptible result from one system and resistant from the other. Minor discrepancy corresponded to having an intermediate interpretation in one system, with a susceptible or resistant result in the other. The level of agreement was analysed using the prevalence adjusted bias adjusted kappa (PABAK).

Results

Overall, the agreement was high, with each ARV being in “almost perfect agreement”, using Landis and Koch’s categorisation. Highest discordance was observed for efavirenz (75/1301, 5.8%), all arising from susceptible Stanford HIVdb versus non-susceptible vircoTYPE™ HIV-1 predictions. Protease Inhibitors had highest level of concordance with PABAKs all above 0.99, followed by Nucleoside Reverse Transcriptase Inhibitors with PABAKs above 0.97 and non-NRTIs with the lowest PABAK of 0.88. The 68/75 patients with discordant efavirenz results harboured the V179D/E mutations compared to 7/1226 with no efavirenz discrepancy (p-value <0.001). In the 3-level comparison, all but one of the discrepancies was minor.

Conclusions

The two systems agreed well with lowest concordance observed for efavirenz. When interpreting HIVDR, especially in non-B subtypes, clinical correlation is crucial, in particular when efavirenz resistance is interpreted based on V179D/E.

Pharmacokinetic study of artemether-lumefantrine given once daily for the treatment of uncomplicated multidrug-resistant falciparum malaria

BACKGROUND

Adherence to antimalarial drug regimens is improved by simple dosing. If the fixed antimalarial drug combination artemether-lumefantrine (AL) could be given once daily, this should improve adherence and thus effectiveness and lower the risk of selecting for resistance.

METHODS

In an open randomized study, 43 patients with uncomplicated falciparum malaria were given equivalent doses of AL with 200 ml flavoured milk either as the conventional twice-daily regimen or as a single daily dose for 3 days. The primary end point was a comparison of the areas under the plasma lumefantrine concentration-time curves (AUC). Secondary end points were the day 42 polymerase chain reaction (PCR)-adjusted cure rates and the tolerability profiles.

RESULTS

Lumefantrine pharmacokinetic profiles were obtained for 36 patients. The AUC((0-->infinity)) of the once-daily regimen was 30% lower than that in the conventional regimen (P = 0.011) with a median (range) value of 306 (114-5781) microg/ml h, compared with 432 (308-992) microg/ml h. There was no significant difference in the peak plasma concentrations reached. PCR-adjusted cure rate estimates at day 42 of follow-up were 94% (95% CI: 84-100) in the six-dose arm and 85% (70-100) in the three-dose arm (P = 0.3).

CONCLUSION

Artemether-lumefantrine efficacy is reduced by once-daily dosing, because absorption of lumefantrine is dose limited. At currently recommended doses, this antimalarial should be given twice daily in a 3-day regimen, with food containing fat.

Pharmacokinetic and pharmacodynamic assessment of co-amoxiclav in the treatment of melioidosis

OBJECTIVES

We conducted a prospective pharmacokinetic study of oral co-amoxiclav in patients with melioidosis to determine the optimal dosage and dosing interval in this potentially fatal infection.

PATIENTS AND METHODS

Serial plasma concentrations were measured after administration of two 1 g tablets of Augmentin (1750 mg of amoxicillin and 250 mg of clavulanate) to 14 adult patients with melioidosis. Monte Carlo simulation was used to predict the concentration of each drug following multiple doses of co-amoxiclav at different dosages and dose intervals. The proportion of the dose-interval above MIC (T > MIC) was calculated from 10,000 simulated subject plasma concentration profiles together with chequerboard MIC data from 46 clinical isolates and four reference strains of Burkholderia pseudomallei.

RESULTS

The median (range) observed maximum plasma concentrations of amoxicillin and clavulanate were 11.5 (3.3-40.2) mg/L and 5.1 (0.8-12.1) mg/L, respectively. The median (range) elimination half-lives were 94 (73-215) and 89 (57-140) min, respectively. Simulation indicated that co-amoxiclav 1750/250 mg given at 4, 6, 8 or 12 hourly dosing intervals would be associated with a T > MIC of < or = 50% in 0.7%, 2.8%, 8.6% and 33.2% of patients, respectively. Corresponding proportions for T > MIC of > or = 90% were 95.8%, 78.6%, 50.2% and 10.8%, respectively.

CONCLUSIONS

The dosing interval for co-amoxiclav (750/250 mg) in melioidosis should not be greater than 6 h.

Efficacy and effectiveness of dihydroartemisinin-piperaquine versus artesunate-mefloquine in falciparum malaria: an open-label randomised comparison

BACKGROUND

Artemisinin-based combinations are judged the best treatments for multidrug-resistant Plasmodium falciparum malaria. Artesunate-mefloquine is widely recommended in southeast Asia, but its high cost and tolerability profile remain obstacles to widespread deployment. To assess whether dihydroartemisinin-piperaquine is a suitable alternative to artesunate-mefloquine, we compared the safety, tolerability, efficacy, and effectiveness of the two regimens for the treatment of uncomplicated falciparum in western Myanmar (Burma).

METHODS

We did an open randomised comparison of 3-day regimens of artesunate-mefloquine (12/25 mg/kg) versus dihydroartemisinin-piperaquine (6.3/50 mg/kg) for the treatment of children aged 1 year or older and in adults with uncomplicated falciparum malaria in Rakhine State, western Myanmar. Within each group, patients were randomly assigned supervised or non-supervised treatment. The primary endpoint was the PCR-confirmed parasitological failure rate by day 42. Failure rates at day 42 were estimated by Kaplan-Meier survival analysis. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN27914471.

FINDINGS

Of 652 patients enrolled, 327 were assigned dihydroartemisinin-piperaquine (156 supervised and 171 not supervised), and 325 artesunate-mefloquine (162 and 163, respectively). 16 patients were lost to follow-up, and one patient died 22 days after receiving dihydroartemisinin-piperaquine. Recrudescent parasitaemias were confirmed in only two patients; the day 42 failure rate was 0.6% (95% CI 0.2-2.5) for dihydroartemisinin-piperaquine and 0 (0-1.2) for artesunate-mefloquine. Whole-blood piperaquine concentrations at day 7 were similar for patients with observed and non-observed dihydroartemisinin-piperaquine treatment. Gametocytaemia developed more frequently in patients who had received dihydroartemisinin-piperaquine than in those on artesunate-mefloquine: day 7, 18 (10%) of 188 versus five (2%) of 218; relative risk 4.2 (1.6-11.0) p=0.011.

INTERPRETATION

Dihydroartemisinin-piperaquine is a highly efficacious and inexpensive treatment of multidrug-resistant falciparum malaria and is well tolerated by all age groups. The effectiveness of the unsupervised treatment, as in the usual context of use, equalled its supervised efficacy, indicating good adherence without supervision. Dihydroartemisinin-piperaquine is a good alternative to artesunate-mefloquine.

A new approach to evaluate regression models during validation of bioanalytical assays

The quality of bioanalytical data is highly dependent on using an appropriate regression model for calibration curves. Non-weighted linear regression has traditionally been used but is not necessarily the optimal model. Bioanalytical assays generally benefit from using either data transformation and/or weighting since variance normally increases with concentration. A data set with calibrators ranging from 9 to 10000 ng/mL was used to compare a new approach with the traditional approach for selecting an optimal regression model. The new approach used a combination of relative residuals at each calibration level together with precision and accuracy of independent quality control samples over 4 days to select and justify the best regression model. The results showed that log-log transformation without weighting was the simplest model to fit the calibration data and ensure good predictability for this data set.

Pitfalls in estimating piperaquine elimination

By using a sensitive new assay, the terminal elimination half-life of the antimalarial piperaquine in a healthy volunteer was estimated to be 33 days, which is longer than estimated previously. This result illustrates the importance of extended sampling duration and sensitive assay methodologies in characterizing the disposition of slowly eliminated antimalarial drugs.

Development and validation of an automated solid phase extraction and liquid chromatographic method for the determination of piperaquine in urine

A sensitive and specific bioanalytical method for determination of piperaquine in urine by automated solid-phase extraction (SPE) and liquid chromatography (LC) has been developed and validated. Buffered urine samples (containing internal standard) were loaded onto mixed phase (cation-exchange and octylsilica) SPE columns using an ASPEC XL SPE robot. Chromatographic separation was achieved on a Chromolith Performance RP-18e (100 mm x 4.6 mm I.D.) LC column with phosphate buffer (pH 2.5; 0.1 mol/L)-acetonitrile (92:8, v/v). Piperaquine was analysed at a flow rate of 3 mL/min with UV detection at 347 nm. A linear regression model on log-log transformed data was used for quantification. Within-day precision for piperaquine was 1.3% at 5000 ng/mL and 6.6% at 50 ng/mL. Between-day precision for piperaquine was 3.7% at 5000 ng/mL and 7.2% at 50 ng/mL. Total-assay precision for piperaquine over 4 days using five replicates each day (n = 20) was 4.0%, 5.2% and 9.8% at 5000, 500 and 50 ng/mL, respectively. The lower limit of quantification (LLOQ) was set to 3 ng/mL using 1 mL of urine, which could be lowered to 0.33 ng/mL when using 9 mL of urine and an increased injection volume.

High throughput assay for the determination of lumefantrine in plasma

A high throughput bioanalytical assay for the determination of lumefantrine in plasma has been developed and validated extensively. The within-day precisions for lumefantrine were 5.2, 3.5 and 2.5% at 200, 2000 and 15000 ng/mL, respectively. The between-day precisions were 4.0, 2.8 and 3.1% at 200, 2000 and 15000 ng/mL, respectively. The lower limits of quantification (LLOQ) and the limits of detection (LOD) were 25 and 10 ng/mL, respectively using 0.250 mL plasma. The average recovery of lumefantrine was 85% and independent upon concentration. The use of 96-well plate format and short chromatographic run has increased the daily sample throughput four times. The assay is particularly suitable for large therapeutic drug monitoring studies using day 7 sampling.

Development and Validation of a Solid-Phase Extraction-Liquid Chromatographic Method for Determination of Amoxicillin in Plasma

A bioanalytic method for the determination of amoxicillin in plasma by hydrophilic interaction solid-phase extraction and liquid chromatography has been developed and validated. Plasma was precipitated with acetonitrile before samples were loaded onto a zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) solid-phase extraction column. Amoxicillin was analyzed by liquid chromatography on an Aquasil (150 x 4.6 mm) LC column with mobile-phase acetonitrile: phosphate buffer (pH 2.5; 0.1 mol/L) (7:93, v/v) and UV detection at 230 nm. A regression model using 1/concentration weighting was found the most appropriate for quantification. The intraassay precision for plasma was 3.3% at 15.0 microg/mL and 10.9% at 0.200 microg/mL. The interassay precision for plasma was 1.8% at 15.0 microg/mL and 7.5% at 0.200 microg/mL. The total-assay precision for plasma over 4 days using a total of 20 replicates was 13.2%, 5.5%, and 3.8% at 0.200 microg/mL, 3.00 microg/mL, and 15.0 microg/mL, respectively. The lower limit of quantification and the limit of detection were 0.050 microg/mL and 0.025 microg/mL, respectively, for 100 microL plasma. Long-term storage stability studies of amoxicillin in plasma indicate that a temperature of -80 degrees C is necessary to prevent degradation of amoxicillin.