The objective of this study was to investigate the effect of
The use of African traditional medicines (ATMs) by HIV/AIDS patients in South Africa is a common phenomenon [
The protease inhibitor (PI), atazanavir (ATV), has a favourable adverse effect profile in comparison to lopinavir; therefore it has been included in the South African clinical guidelines for the management of HIV/AIDS in adults and adolescents (2010), as an alternative to lopinavir in patients who experience intolerable gastrointestinal problems, hyperlipidaemia or hyperglycemia [
SF is a South African plant which has a long history of use in the practice of traditional medicine, particularly by the
ATV sulphate (100.9%) was donated by Aspen Pharmacare (Port Elizabeth, South Africa), and diazepam (DIAZ) was obtained from the Biopharmaceutics Research Institute (Rhodes University, Grahamstown, South Africa). HPLC grade acetonitrile was purchased from Romil Ltd. (Cambridge, United Kingdom). Water was purified by reverse osmosis and filtration through a Milli-Q purification system (Millipore, Milford, M A, USA). Sodium carbonate (99.5%) and ethyl acetate (99–101%) were provided by BDH Laboratory Reagents (Poole, England) and formic acid (99.9%) from Associated Chemical Enterprises Pty Ltd. (Johannesburg, South Africa), whilst n-Hexane (≥98%) was purchased from Merck (Darmstadt, Germany). Fresh human plasma with potassium edetate (K-EDTA) as an anticoagulant was obtained from the South African National Blood Services, Eastern Cape Headquarters (Port Elizabeth, South Africa) and was stored at 4 ± 2°C. Medication used in the clinical study was Reyataz 200 mg ATV sulphate capsules from Bristol-Myers Squibb, Bedfordview, Gauteng, South Africa, and Sutherlandia SU1 300 mg SF tablets from Phyto Nova, Cape Town, Western Cape, South Africa. Analysis of these tablets revealed that triterpenoid glycosides, namely, Sutherlandiosides A, B, C, and D were present at 0.05, 3.02, 0.93, and 0.46 mg/tablet, respectively, while 0.63, 0.67, 1.49, and 0.99 mg/tablet of flavonol glycosides, namely, Sutherlandins A, B, C, and D respectively, were quantified.
Twelve non-smoking, HIV-negative, healthy male subjects between the ages 18 and 55 years and with a body mass index (BMI) between 19 and 30 kg/m2 were enrolled into the study after giving informed consent and passing a medical, physical, and laboratory screening within one month prior to commencement of the study. The screening included laboratory tests for liver function, hepatitis B and C, and HIV, as well as blood biochemistry, urinalysis, and drugs-of-abuse, such as amphetamines, barbiturates, benzodiazepines, cocaine, methamphetamine, morphine, phencyclidine, tetrahydrocannabinol, tricyclic antidepressants, and alcohol.
The subjects were required to adhere to study restrictions which included no prescription or over-the-counter medicines from one week before the start of the study, no alcohol from four days before the start of the study, and no caffeine and grapefruit juice from 48 hours before the start of the study. Subjects were also prohibited from participating in strenuous exercise from 24 hours before each of the two phases of the study.
Ethical approval was granted by the Rhodes University Ethical Standards Committee to conduct a one-sequence crossover, two phase clinical study with a single dose/multiple dose regimen combination for ATV and SF, respectively. The study was conducted according to the South African Good Clinical Trials guideline [
The night before the start of the study (Day 0), subjects checked into the clinic and were screened for drugs of abuse and probed to determine compliance with the study restrictions. On Day 1 of the study (start of Phase I), subjects received a light meal before a single 400 mg (2 × 200 mg capsules) dose of ATV (Reyataz, Bristol-Myers Squibb, Bedfordview, Gauteng, South Africa) was administered to each with a 240 mL glass of water. A mouth and hand check was conducted to confirm that the dose had been ingested. Subjects were not permitted to lie down or sleep until 4 hours after dose, unless this was necessary due to an adverse event. Standard meals were provided until 24 hours post-dose. The time at which each subject commenced and ended each meal was recorded as well as the approximate amount consumed.
Ten-millilitre blood samples were collected into BD Vacutainer blood collection tubes (Becton Dickinson, Woodmead, Gauteng, South Africa) containing potassium EDTA as the anticoagulant, at the following time intervals: before dosing (0) and at 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0, 9.0, 12, 18, and 24 hours post-dose. The exact time at which each sample was withdrawn was also recorded.
From Day 3, each subject started a twice daily regimen (one tablet twice a day) of Sutherlandia SU1 tablets (Phyto Nova, Cape Town, Western Cape, South Africa). The label of Sutherlandia SU1 stated that each tablet contained 300 mg of SF plant material. Subjects reported to the study investigator every day between 08h00 and 09h00 and between 20h00 and 21h00 to receive these doses with a 240 mL glass of water. A hand and mouth check was carried out to confirm that these doses were taken. On Day 14, the subjects checked into the clinic for screening as described for Day 0. On Day 15 (start of Phase II), each subject received a single oral dose of ATV (2 × 200 mg capsules) and a dose (1 × 300 mg tablet) of Sutherlandia SU1, 30 minutes after a light meal. The rest of Phase II was conducted according to the same procedures described for Phase I. Dropouts at any time during the study were not replaced.
Blood samples from both phases were stored in an ice-bath immediately after withdrawal up until centrifugation at 2800 ×g for 10 minutes at 4°C, which was done within 30 minutes. Duplicate aliquots of harvested plasma were stored in polypropylene tubes at −80 ± 10°C until transfer to the analytical laboratory, where the samples were stored at −10 ± 2°C. The tubes were labelled with the study number, phase number, subject number, sample number, and sampling time
A pilot clinical study [
The HPLC system consisted of an Alliance 2695 Separations module and a 2996 Waters photodiode array UV detector coupled to empower data acquisition software (Waters, Milford, MA, USA). A Luna C18 (2) (5
The PK parameters of ATV before and after co-administration with SF were determined by non-compartmental analyses. Exposure measures,
Equiv Test (Statcon, Witzenhausen, Germany) was used to construct 90% CIs about the equivalence parameter and geometric mean ratio (difference of means on natural log scale) for
Of the 12 healthy male subjects enrolled to participate in the study, 8 (66.7%) were black, 3 (25%) were white, and 1 (8.3%) was Indian; the mean age was 23 years (range, 19–30 years) and an average BMI of 23.5 Kg/m2 (range, 20.2–27.6 Kg/m2) was recorded. The study was completed without any major protocol deviations. There were no subject dropouts and no adverse events were reported.
Figure
Non-compartmental and statistical analysis of PK parameters of ATV.
Pharmacokinetic parameter | Phase I |
Phase II |
Phase II/Phase I |
---|---|---|---|
AUC0–24 ( |
13.0 |
10.0 |
0.801 |
|
3.17 |
2.59 |
0.783 |
|
2.71 |
2.67 |
N/A |
|
3.77 |
3.82 |
N/A |
|
0.205 |
0.200 |
N/A |
Comparison of ATV plasma concentration-time profiles for Phase I (ATV alone) and Phase II (ATV + SF). Each point represents the mean ± SD;
The significant reduction in the bioavailability of ATV, in the presence of SF may have occurred due to a decrease in absorption and/or enhanced metabolism of ATV. Potential mechanisms underlying the effect include an increase in the activities and/or the expression of influx and/or efflux transporters, such as P-gp and/or metabolic enzymes such as CYP3A4/5 in the small intestines and/or livers of some of the subjects. Protein expression via induction may only occur after chronic rather than acute administration of a xenobiotic, whilst modulation of the activity of the transporters and enzymes may manifest even after acute administration of the potential interacting agent.
The similar rate of elimination observed between the two phases from 4 to 24 hours post-dose may indicate that SF did not alter post-absorption metabolism or transport pathways of ATV which occur as part of the elimination process in the liver and that the observed decrease in bioavailability of ATV was more likely due to a reduction in the transport and/or an increase in metabolism of ATV during the absorption process in the small intestine. This may imply that the change in activity and/or expression of transporters and/or metabolic enzymes in the small intestines was greater than in the livers of susceptible subjects. To exert an effect in the liver, the “active” phytochemical constituents of SF must be absorbed across the intestinal epithelium into the systemic circulation. The absorption of at least one of the triterpenoid glycosides present in SF may be impeded, since
The clinical relevance of the potential interaction between SF and ATV is difficult to predict since only a single dose of ATV was evaluated, yet clinically, ATV is dosed chronically. It is therefore not known how SF may affect the steady-state PK of ATV, and thus whether subtherapeutic levels of ATV may result. The bioavailability of ATV is reduced in HIV patients in comparison to healthy subjects [
The PK of ATV has been found to be influenced by CYP3A5 and P-gp genetic polymorphisms [
A significant decrease in the steady state
A two-week regimen of Phyto Nova Sutherlandia SU1 tablets which contain SF plant material significantly reduced the
Adrienne Müller gratefully acknowledges scholarships from the Atlantic Philanthropies Fund, Rhodes University, and the National Research Foundation of South Africa. The authors also acknowledge Dr. Bharathi Avula of the National Centre for Natural Products Research, Research Institute of Pharmaceutical Sciences at the University of Mississippi, for conducting the quantitative analysis of triterpenoid and flavonol glycoside content in the batch of Phyto Nova Sutherlandia SU1 tablets used in the study.