Medical Science Liaisons (MSL) in Africa: a perspective

The role of a Medical Science Liaison (MSL) is of growing importance to pharmaceutical, biotechnology, diagnostic and medical device companies. Through scientific engagement MSLs add value to clinical practice, ultimately benefiting patients. The MSL role is dynamic and encompasses in-depth product and disease knowledge together with the ability to communicate relevant, unbiased scientific information concisely and timely. Tasks are focused on contributing towards the advancement of medical knowledge, scientific data generation and dissemination. Professional relationships are developed, fostering collaboration between external experts and typically the medical affairs departments of pharmaceutical companies through a credible liaison. Through such relationships, critical insights are shared that shape the development pipeline, promote successful clinical translation and guide the market deployment strategy of therapeutic interventions through-out their life cycle. Despite the rising number of MSLs in the field and the implicit medical value of the role, there remains a lack of understanding for what the roles of a MSL entails. In Africa, where exponential growth of the pharmaceutical industry is expected, the number of MSLs will increase rapidly. Given the complexities of the African continent, the MSLs in this burgeoning environment will face various challenges including remote locations, time-constraints, regulatory and bureaucratic hurdles and importantly physician misperception of the MSL role that collectively may thwart the goal of meaningful scientific engagement; but these challenges can be surmounted through astute proactive planning and utilization of opportunities including digital communication strategies.

Long-term safety and efficacy of alirocumab in South African patients with heterozygous familial hypercholesterolaemia: the ODYSSEY Open-Label Extension study

BACKGROUND

Alirocumab reduces low-density lipoprotein cholesterol (LDL-C) levels by up to 61%. The ODYSSEY Open-Label Extension study investigated the effect of alirocumab in patients with heterozygous familial hypercholesterolaemia (HeFH) over 144 weeks.

METHODS

Eligible patients with HeFH had completed an earlier double-blind, randomised, placebo-controlled parent study. Patients were initiated on 75 mg alirocumab Q2W subcutaneous (SC) unless baseline LDL-C was > 8.9 mmol/l, in which case they received 150 mg alirocumab Q2W. Dose titration to 150 mg Q2W was at the investigator's discretion.

RESULTS

The study enrolled 167 patients and the parent study mean (± SD) baseline LDL-C level was 3.65 ± 1.9 mmol/l. Mean LDL-C level was reduced by 48.7% at week 144; mean on-treatment LDL-C was 2.30 ± 1.24 mmol/l. Eight patients reported injection-site reactions, with one treatment discontinuation. Treatment emergent anti-drug antibodies were identified in five patients but these did not affect the efficacy.

CONCLUSIONS

Alirocumab effectively and safely reduced LDL-C in these patients.

Improving rifampicin-resistant tuberculosis diagnosis using Xpert® MTB/RIF: modelling interventions and costs

SETTING

Cape Town, South Africa.

OBJECTIVE

To model the diagnosis of rifampicin-resistant tuberculosis (RR-TB) and laboratory costs of smear/culture and Xpert-based algorithms and the effect of varying adherence and human immunodeficiency virus (HIV) testing in the Xpert-based algorithm.

METHODS

We used a validated operational model (100 000 population) and published laboratory cost data. We estimated the number and cost of RR-TB cases identified using the smear/culture- and Xpert-based algorithms. We modelled varying adherence and different levels of known HIV status against the Xpert-based algorithm.

RESULTS

The number of RR-TB cases identified increased from 603 with smear/culture to 1178 with the Xpert-based algorithm (100% adherence; 60% knew their HIV status). The overall laboratory cost increased from US$1 073 858 to US$2 430 050 and the cost per RR-TB case identified increased from US$1781 to US$2063 in the respective algorithms. When adherence to the Xpert-based algorithm was increased from 50% to 100% (60% knew their HIV status), the number of RR-TB cases identified increased from 721 to 1178.

CONCLUSION

The Xpert-based algorithm is efficient in identifying RR-TB, as the increase in costs is offset by the increase in the number of cases identified. Adherence to the Xpert-based algorithm is important to ensure that all presumptive TB cases receive the benefit of simultaneous TB and RR-TB testing.

Management of low-density lipoprotein cholesterol levels in South Africa: the International ChoLesterol management Practice Study (ICLPS)

The International Cholesterol Management Practice Study (ICLPS) South Africa investigated achievement of European Society of Cardiology (ESC)/European Atherosclerosis Society (EAS) guideline low-density lipoprotein cholesterol (LDL-C) targets in real-world clinical practice. Demographic data, clinical characteristics, cardiovascular risk factors, lipid-modifying medications, lipid values and investigator's assessment of cardiovascular risk were recorded for 396 patients on stable lipid-modifying therapy. Most (98.7%) patients received statins; 25.1% of statin-treated patients were receiving high-intensity statins. Overall, 41.4% of patients achieved their LDL-C target; among 354 (89.4%) patients in whom cardiovascular disease risk, based on ESC Systematic Coronary Risk Estimation (SCORE) was calculated, achievement rate was 14.3% for moderate-risk (n = 7), 59.3% for high-risk (n = 123) and 32.3% for very high-risk patients (n = 223). Half of Asian (54.7%) and black African (53.2%) patients were at LDL-C target compared with 29.8% of European/Caucasian and 27.3% of 'other' patients. Improved guideline adherence and greater use of combination therapy may increase LDL-C goal achievement.

Viscosupplementation for knee osteoarthritis: a focus on Hylan G-F 20

Knee osteoarthritis is a chronic degenerative joint disease characterized by destruction of articular cartilage with resultant para-articular bone changes. It is a major cause of disability in older persons and is managed by surgical and nonsurgical interventions. Pharmacotherapy includes acetaminophen, nonsteroidal anti-inflammatory agents, and intra-articular steroids. Another treatment option is viscosupplementation with intra-articular injection of hyaluronan (HA). The full mechanism of action of exogenous HA is uncertain, but studies indicate that it may promote endogenous HA production, reduce inflammation, prevent degeneration of cartilage and promote cartilage regeneration. Clinically, HA may improve symptoms of osteoarthritis and delay time to total knee replacement surgery. However, clinical studies are heterogenous and of varying quality, and thus there is a need for more robust studies to determine the place of viscosupplementation in the management of knee osteoarthritis.

Does the use of adjunct urine lipopolysaccharide lipoarabinomannan in HIV-infected hospitalized patients reduce the utilization of healthcare resources? A post hoc analysis of the LAM multi-country randomized controlled trial

BACKGROUND

The World Health Organization (WHO) recommends the use of adjunctive urine lipopolysaccharide lipoarabinomannan (LAM) testing in hospitalized HIV-infected persons with suspected tuberculosis (TB) and a CD4 count <100cells/ml. However, the recommendation is conditional, and uptake by individual treatment programmes depends on perceived additional benefit. The aim of this study was to determine whether adjunctive LAM testing has additional clinical benefits including a reduction in healthcare-related use of resources.

METHODS

A post hoc analysis was performed of a published multicentre, multi-country, randomized controlled trial that showed an approximate 20% mortality benefit in HIV-infected hospitalized patients who underwent adjunctive LAM testing as part of their diagnostic workup. In that parent study, adult HIV-infected hospitalized patients with suspected TB (n=2528) were randomly allocated to either routine diagnostics (smear microscopy, Xpert MTB/RIF, and culture; n=1271), or routine diagnostics plus adjunctive urine LAM testing (n=1257). Data were further analyzed to determine whether there were other potential benefits of LAM usage based on CD4 count and illness severity. Aspects evaluated included: (1) the reduction in number of diagnostic sputum samples tested, (2) the utilization of additional imaging, (3) disease resolution based on follow-up signs and symptoms of illness severity, and (4) the reduction in hospital readmission.

RESULTS

Adjuvant LAM did not reduce the number of diagnostic sputum samples requested, the need for additional imaging, or the hospital readmission rate. However, adjunctive LAM was associated with a more rapid rate of disease resolution (dyspnoea) in the severely ill subgroup. Higher LAM grade (grades 4 and 5), compared to lower grade positivity (≤3), was associated with lower use of ultrasound, lower Karnofsky performance score, lower CD4 cell count, and shorter time to culture positivity.

CONCLUSIONS

Although, adjunct LAM was associated with a mortality benefit in the parent study, no benefit could be demonstrated in the secondary analysis with respect to the number of diagnostic sputum samples requested, the use of additional imaging, or hospital readmission rates. However, given the limitations of the present study, further appropriately designed studies are required to determine the effect of adjunct urine LAM on the utilization of healthcare resources.

Non-referral of potential organ donors in South Africa: insights, challenges and ethical dilemmas

Traditionally, minimal potential organ donor referrals emanate from general medicine departments. We use a clinical vignette to draw attention to challenges related to referral of potential organ donors from general internal medicine departments. In addition, we provide potential solutions to overcome challenges and reflect on the ethical issues of non-referral of potential organ donors. It is hoped that this paper will increase the awareness of organ donation in the medical fraternity in Africa and thus mitigate critical shortages of organs for transplantation.

Therapeutic Management of Dyslipidemia Patients at Very High Cardiovascular Risk (CARDIO TRACK): Protocol for the Observational Registry Study

BACKGROUND

Dyslipidemia is a major modifiable risk factor for atherosclerotic cardiovascular disease. Current South African guidelines recommend titrating lipid-lowering therapy (LLT) to low-density lipoprotein cholesterol (LDL-C) targets stratified by cardiovascular risk. The LDL-C goal for very high-risk patients is <1.8 mmol/L. In international studies, approximately 30% of patients do not achieve this goal despite receiving maximally tolerated statin doses. There is, however, a paucity of data on LDL-C goal achievement in very high-risk South African patients receiving maximal statin doses.

OBJECTIVE

The goal of the research it to assess LDL-C goal achievement in, and clinical characteristics of, very high cardiovascular risk dyslipidemic patients receiving maximal tolerated statin doses with or without ezetimibe.

METHODS

This is an observational, cross-sectional South African registry study that plans to include up to 30 sites and 500 study participants. Adult patients with very high cardiovascular risk status receiving stable, maximally tolerated statin doses (with or without ezetimibe) will be eligible for inclusion.

RESULTS

Funding has been awarded and enrollment began on November 15, 2017, and was completed on April 13, 2018, with 507 participants. Database lock was done on June 21, 2018. The statistical analysis has commenced and we expect the final clinical study report to be completed by October 2018.

CONCLUSIONS

This study will document the adequacy of LLT in those at highest risk and will thus fill an important data gap in South Africa. This data may be useful in assessing the need for novel LLTs like proprotein convertase subtilisin/kexin 9 inhibitors that substantially lower cholesterol levels in addition to optimal statin therapy.

REGISTERED REPORT IDENTIFIER

RR1-10.2196/9248.

Marfan syndrome: a case report and pictorial essay

We report a case of Marfan syndrome (MFS) in a South African patient, which is extraordinary because of the large constellation of clinical, radiological and vascular anomalies in a single patient. A literature search from 1950 to date did not show a similar report of such extensive clinical characteristics of MFS.

Paraoxonase (PON)-1: a brief overview on genetics, structure, polymorphisms and clinical relevance

Paraoxonase-1 (PON1) is a high-density lipoprotein-associated esterase and is speculated to play a role in several human diseases including diabetes mellitus and atherosclerosis. Low PON1 activity has been associated with increased risk of major cardiovascular events, therefore a variety of studies have been conducted to establish the cardioprotective properties and clinical relevance of PON1. The major aim of this review was to highlight the important studies and to subsequently assess if PON1 has clinical relevance. A review of the literature showed that there is currently insufficient data to suggest that PON1 has clinical relevance. It is our opinion that robust studies are required to clarify the clinical relevance of PON1.

Maternal miRNA-146a G/C rs2910164 variation, HIV/AIDS and nitrogen oxide pollution exposure collectively affects foetal growth

OBJECTIVE:

Nitrogen oxide (NOx) pollution and human immunodeficiency virus (HIV)/AIDS intensify inflammation during pregnancy and linked with adverse birth outcomes (ABOs). MicroRNA (miRNA)-146a plays a crucial role in regulating inflammation in the NF-κB pathway. The G/C rs2910164 dampens miRNA-146a activity and linked with inflammatory diseases. The present study investigated whether HIV/AIDS and NOx exposure throughout pregnancy further intensifies ABO in Black South African women genotyped for the rs2910164.

METHODS:

Pregnant women ( n = 300) were subdivided into low, medium and high NOx exposure groups, genotyped for the miRNA-146a G/C rs2910164 using polymerase chain reaction-restriction fragment length polymorphism, and further stratified based on HIV status.

RESULTS:

Unstratified data (HIV+ and HIV- mothers combined): Mothers from the high NOx group with the variant C-allele had low blood iron levels ( p = 0.0238), and had babies with reduced birthweights ( p = 0.0283). As NOx increased, the prevalence of preterm birth and low birth weight also increased in mothers with the variant C-allele versus wildtype G-allele. HIV-infected mothers: In all NOx exposure groups, mothers with the variant C-allele had higher systolic blood pressure (low: p = 0.0386, medium: p = 0.0367 and high: p = 0.0109) and had babies with lower Appearance, Pulse, Grimace, Activity and Respiration scores at 1 min (low: p = 0.0190, medium: p = 0.0301 and high: p = 0.0361).

CONCLUSION:

Maternal rs2910164 variant C-allele, NOx pollution and HIV/AIDS might collectively play a role in intensifying gestational hypertension and ABO.

High laboratory cost predicted per tuberculosis case diagnosed with increased case finding without a triage strategy

SETTING

Cape Town, South Africa.

OBJECTIVE

To model the effects of increased case finding and triage strategies on laboratory costs per tuberculosis (TB) case diagnosed.

METHODS

We used a validated operational model and published laboratory cost data. We modelled the effect of varying the proportion with TB among presumptive cases and Xpert cartridge price reductions on cost per TB case and per additional TB case diagnosed in the Xpert-based vs. smear/culture-based algorithms.

RESULTS

In our current scenario (18.3% with TB among presumptive cases), the proportion of cases diagnosed increased by 8.7% (16.7% vs. 15.0%), and the cost per case diagnosed increased by 142% (US$121 vs. US$50). The cost per additional case diagnosed was US$986. This would increase to US$1619 if the proportion with TB among presumptive cases was 10.6%. At 25.9-30.8% of TB prevalence among presumptive cases and a 50% reduction in Xpert cartridge price, the cost per TB case diagnosed would range from US$50 to US$59 (comparable to the US$48.77 found in routine practice with smear/culture).

CONCLUSION

The operational model illustrates the effect of increased case finding on laboratory costs per TB case diagnosed. Unless triage strategies are identified, the approach will not be sustainable, even if Xpert cartridge prices are reduced.

Operational modelling: the mechanisms influencing TB diagnostic yield in an Xpert® MTB/RIF-based algorithm

SETTING

Cape Town, South Africa.

OBJECTIVE

To compare the diagnostic yield for smear/culture and Xpert® MTB/RIF algorithms and to investigate the mechanisms influencing tuberculosis (TB) yield.

METHOD

We developed and validated an operational model of the TB diagnostic process, first with the smear/culture algorithm and then with the Xpert algorithm. We modelled scenarios by varying TB prevalence, adherence to diagnostic algorithms and human immunodeficiency virus (HIV) status. This enabled direct comparisons of diagnostic yield in the two algorithms to be made.

RESULTS

Routine data showed that diagnostic yield had decreased over the period of the Xpert algorithm roll-out compared to the yield when the smear/culture algorithm was in place. However, modelling yield under identical conditions indicated a 13.3% increase in diagnostic yield from the Xpert algorithm compared to smear/culture. The model demonstrated that the extensive use of culture in the smear/culture algorithm and the decline in TB prevalence are the main factors contributing to not finding an increase in diagnostic yield in the routine data.

CONCLUSION

We demonstrate the benefits of an operational model to determine the effect of scale-up of a new diagnostic algorithm, and recommend that policy makers use operational modelling to make appropriate decisions before new diagnostic algorithms are scaled up.

Tuberculosis in adolescents and young adults: epidemiology and treatment outcomes in the Western Cape

SETTING

Western Cape Province, South Africa.

OBJECTIVES

To characterise tuberculosis (TB) epidemiology, disease presentation and treatment outcomes among adolescents (age 10-19 years) and young adults (age 20-24 years) in the Western Cape.

DESIGN

A retrospective, cross-sectional review of routine patient-level data from the Electronic TB Register (ETR.Net) for 2013. Site of TB disease, human immunodeficiency virus (HIV) status and TB treatment outcomes were analysed by 5-year age groups (<5, 5-9, 10-14, 15-19, 20-24 and 25 years of age). TB notification rates were calculated using census data.

RESULTS

Adolescents and young adults comprised 18.0% of all new TB notifications in 2013. The notification rate was 141 TB cases/100 000 person-years (py) among 10-14 year olds, 418/100 000 py among 15-19 year olds and 627/100 000 py among 20-24 year olds. HIV prevalence among TB patients was 10.9% in 10-14 year olds, 8.8% in 15-19 year olds and 27.2% in 20-24 year olds. Older adolescents (age 15-19 years) and young adults (age 20-24 years) with HIV co-infection had poor treatment outcomes: 15.6% discontinued treatment prematurely and 4.0% died.

CONCLUSIONS

Young people in the Western Cape suffer a substantial burden of TB, and those with TB-HIV co-infection are at high risk of treatment discontinuation.

Comparing laboratory costs of smear/culture and Xpert® MTB/RIF-based tuberculosis diagnostic algorithms

SETTING

Cape Town, South Africa, where Xpert^® MTB/RIF was introduced as a screening test for all presumptive tuberculosis (TB) cases.

OBJECTIVE

To compare laboratory costs of smear/culture- and Xpert-based tuberculosis (TB) diagnostic algorithms in routine operational conditions.

METHODS

Economic costing was undertaken from a laboratory perspective, using an ingredients-based costing approach. Cost allocation was based on reviews of standard operating procedures and laboratory records, timing of test procedures, measurement of laboratory areas and manager interviews. We analysed laboratory test data to assess overall costs and cost per pulmonary TB and multidrug-resistant TB (MDR-TB) case diagnosed. Costs were expressed as 2013 Consumer Price Index-adjusted values.

RESULTS

Total TB diagnostic costs increased by 43%, from US$440 967 in the smear/culture-based algorithm (April-June 2011) to US$632 262 in the Xpert-based algorithm (April-June 2013). The cost per TB case diagnosed increased by 157%, from US$48.77 (n = 1601) to US$125.32 (n = 1281). The total cost per MDR-TB case diagnosed was similar, at US$190.14 and US$183.86, with 95 and 107 cases diagnosed in the respective algorithms.

CONCLUSION

The introduction of the Xpert-based algorithm resulted in substantial cost increases. This was not matched by the expected increase in TB diagnostic efficacy, calling into question the sustainability of this expensive new technology.

The association between biopsychosocial factors and disability in a national health survey in South Africa

The association between psychosocial factors and disability is less clear. This study investigated the biological and psychosocial (employment and psychological distress) factors associated with level of disability in an adult sample in South Africa. Data were analysed from a cross-sectional survey among adults aged 18-64 (n = 4974). Multiple linear regression was used to investigate the associations of the selected variables with disability. The mean percentage score on the WHODAS scale of disability was 5.31% (95% CI: 4.74-5.88). Age (p < 0.001) and race (p = 0.0002) were significantly associated with disability, and history of stroke (β = 7.19, 95% CI: 3.19-11.20) and heart-related conditions (β = 2.08, 95% CI: [0.23-3.93) showed positive associations. Of the psychosocial variables, psychological distress (β = 10.49 [8.63-12.35]) showed a strong positive association while employment (-1.62 [-2.36 to -0.88]) showed a negative association with disability. The association between demographic factors, medical conditions and increased disability confirms the findings in the literature. The finding that psychological distress is associated with increased disability has not been frequently reported. This study highlights specific psychosocial targets that may be usefully addressed by health policies and interventions in order to improve disability management.

Assessment of certain ionic liquids for separation of binary mixtures based on gamma infinity data measurements

Limiting activity coefficients for 64 solutes in [BzMIM][NTf₂] and [BzMIM][DCA], the gas–liquid partition coefficients, K_L, thermodynamic functions and selectivity for hexane/hex-1-ene, cyclohexane/cyclohexene and ethylbenzene/styrene separation were presented.

Glibenclamide population pharmacokinetic/pharmacodynamic modeling in South African type 2 diabetic subjects

Aim

Patients and methods

Results

Conclusion

Effect of Sitagliptin and Metformin on Prediabetes Progression to Type 2 Diabetes - A Randomized, Double-Blind, Double-Arm, Multicenter Clinical Trial: Protocol for the Sitagliptin and Metformin in PreDiabetes (SiMePreD) Study

Background

The high prevalence and incidence of type 2 diabetes mellitus (DM), and its associated morbidity and mortality, has prompted growing international interest and effort in the primary prevention of this disease. Primary prevention is possible since type 2 DM is preceded by prediabetes, offering a window opportunity to treat patients, and prevent the emergence of advanced disease. Sitagliptin is an oral dipeptidyl peptidase-IV inhibitor that preserves existing beta cell function and increases beta cell mass. These two effects have been demonstrated both in vitro and in animal studies, and current clinical data show that sitagliptin is safe. Metformin, a biguanide, reduces insulin resistance and inhibits hepatic gluconeogenesis, and has an excellent safety profile. The combination of metformin and sitagliptin, targeting both characteristics of prediabetes (insulin resistance and progressive beta cell degeneration), may potentially slow or halt the progression from prediabetes to type 2 DM. This paper describes the rationale and design of the Sitagliptin and Metformin in PreDiabetes (SiMePreD) study.

Objective

The aim of this study is to determine the effect of sitagliptin and metformin on progression from prediabetes to type 2 DM. The objectives of the study are to determine the effects of metformin and placebo on glycemic endpoints, the effects of sitagliptin and metformin on glycemic endpoints, the effects of metformin and placebo on incidence of cardiovascular disease and death, and the effects of sitagliptin and metformin on incidence of cardiovascular disease and death.

Methods

This is a randomized, double-blind, multicenter clinical study that will determine if the combination of metformin and sitagliptin is effective in preventing the progression from prediabetes to type 2 DM. The study will contain two arms (metformin/sitagliptin and metformin/placebo). Primary endpoints include the number of subjects progressing from prediabetes to type 2 DM, the number of cardiovascular events, and the number of deaths. The planned duration of the study is five years, and 410 subjects will be included in each group. Data analyses will include clinically relevant measures (eg, numbers needed to treat and numbers needed to harm) and will be performed according to the intention-to-treat principle.

Results

This study is currently in the process of acquiring research funding.

Conclusions

The SiMePreD study is the first study to investigate the utility of sitagliptin in combination with metformin for the primary prevention of type 2 DM. 

Psychopathology in Urban and Rural/Peri-Urban Children Seeking Mental Health Care

While childhood psychopathology may not necessarily be expected to vary between urban and rural children, social and political factors could be influential in the variances in presentation across these different environments. A comparative investigation was undertaken in the KwaZulu-Natal region to examine childhood presentations at (i) an urban psychological clinic in a low socio-economic environment, and (ii) a few visiting psychological clinics serving rural and peri-urban communities. Data were collected over a five-year period. The results revealed several notable differences, for example, attention-deficit/hyperactivity disorder (ADHD) and disruptive behaviour disorders (other than ADHD) were significantly more prevalent in the urban sample. However, mental retardation, post-traumatic stress disorder and sexual abuse were significantly more common in the rural/peri-urban sample. The results are discussed within the context of children's life experiences, available facilities, and psychopathology detection rates in these two types of environments.

Global-to-local policy transfer in the introduction of new molecular tuberculosis diagnostics in South Africa

SETTING

Lack of innovation in diagnostics has contributed to tuberculosis (TB) remaining a global health challenge. It is critical to understand how new diagnostic technologies are translated into policies and how these are implemented.

OBJECTIVE

To examine policy transfer for two rapid molecular diagnostic tests, GenoType(®) MDRTBplus and Xpert(®) MTB/RIF, to understand policy development, uptake and implementation in South Africa.

METHODS

A policy transfer analysis framework integrating the key dimensions of policy transfer into one coherent model was used. Two phases of key informant interviews were undertaken with a wide range of stakeholders.

RESULTS

Both tests were developed through innovative partnerships and responded to urgent public health needs. GenoType was introduced through a process that was more inclusive than that for Xpert. National policy and planning processes were opaque for both tests. Their implementation, maintenance and expansion suffered from poor communication and coordination, insufficient attention to resource implications, technical challenges and a lack of broader health systems thinking.

CONCLUSION

Our analysis identified the risks and benefits of partnerships for technological innovation, the complex intersections between global and national actors and the impact of health systems on policy transfer, and the risks of rescue- and technology-focused thinking in addressing public health challenges.

Population pharmacokinetic modeling of glibenclamide in poorly controlled South African type 2 diabetic subjects

Aim

The aim of this study was to describe the pharmacokinetics (PK) of glibenclamide in poorly controlled South African type 2 diabetic subjects using noncompartmental and model-based methods.

Methods

A total of 24 subjects with type 2 diabetes were administered increasing doses (0 mg/d, 2.5 mg/d, 5 mg/d, 10 mg/d, and 20 mg/d) of glibenclamide daily at 2-week intervals. Plasma glibenclamide, glucose, and insulin determinations were performed. Blood sampling times were 0 minute, 30 minutes, 60 minutes, 90 minutes, and 120 minutes (post breakfast sampling) and 240 minutes, 270 minutes, 300 minutes, 330 minutes, 360 minutes, and 420 minutes (post lunch sampling) on days 14, 28, 42, 56, and 70 for doses of 0 mg, 2.5 mg, 5.0 mg, 10 mg, and 20 mg, respectively. Blood sampling was performed after the steady state was reached. A total of 24 individuals in the data set contributed to a total of 841 observation records. The PK was analyzed using noncompartmental analysis methods, which were implemented in WinNonLin^®, and population PK analysis using NONMEM^®. Glibenclamide concentration data were log transformed prior to fitting.

Results

A two-compartmental disposition model was selected after evaluating one-, two-, and three-compartmental models to describe the time course of glibenclamide plasma concentration data. The one-compartment model adequately described the data; however, the two-compartment model provided a better fit. The three-compartment model failed to achieve successful convergence. A more complex model, to account for enterohepatic recirculation that was observed in the data, was unsuccessful.

Conclusion

In South African diabetic subjects, glibenclamide demonstrates linear PK and was best described by a two-compartmental model. Except for the absorption rate constant, the other PK parameters reported in this study are comparable to those reported in the scientific literature. The study is limited by the small study sample size and inclusion of poorly controlled type 2 diabetic subjects.