Pharmacokinetic and pharmacogenomic modelling of the CYP3A activity marker 4ß-hydroxycholesterol during efavirenz treatment and efavirenz/rifampicin co-treatment.

OBJECTIVES: To assess the effect of the major efavirenz metabolizing enzyme (CYP2B6) genotype and the effects of rifampicin co-treatment on induction of CYP3A by efavirenz. PATIENTS AND METHODS: Two study arms (arm 1, n = 41 and arm 2, n = 21) were recruited into this study. In arm 1, cholesterol and 4ß-hydroxycholesterol were measured in HIV treatment-naive patients at baseline and then at 4 and 16 weeks after initiation of efavirenz-based antiretroviral therapy. In arm 2, cholesterol and 4ß-hydroxycholesterol were measured among patients taking efavirenz during rifampicin-based tuberculosis (TB) treatment (efavirenz/rifampicin) just before completion of TB treatment and then serially following completion of TB treatment (efavirenz alone). Non-linear mixed-effect modelling was performed. RESULTS: A one-compartment, enzyme turnover model described 4ß-hydroxycholesterol kinetics adequately. Efavirenz treatment in arm 1 resulted in 1.74 (relative standard error = 15%), 3.3 (relative standard error = 33.1%) and 4.0 (relative standard error = 37.1%) average fold induction of CYP3A for extensive (CYP2B6*1/*1), intermediate (CYP2B6*1/*6) and slow (CYP2B6*6/*6) efavirenz metabolizers, respectively. The rate constant of 4ß-hydroxycholesterol formation [mean (95% CI)] just before completion of TB treatment [efavirenz/rifampicin co-treatment, 7.40 × 10(-7) h(-1) (5.5 × 10(-7)-1.0 × 10(-6))] was significantly higher than that calculated 8 weeks after completion [efavirenz alone, 4.50 × 10(-7) h(-1) (4.40 × 10(-7)-4.52 × 10(-7))]. The CYP3A induction dropped to 62% of its maximum by week 8 of completion. CONCLUSIONS: Our results indicate that efavirenz induction of CYP3A is influenced by CYP2B6 genetic polymorphisms and that efavirenz/rifampicin co-treatment results in higher induction than efavirenz alone.

Responsiveness of the EAT-10 to Clinical Change in Head and Neck Cancer Patients with Dysphagia.

Purpose: This retrospective study evaluated the external responsiveness of the Eating Assessment Tool-10 (EAT-10) to clinical changes in a single cohort (n = 105) treated with chemoradiotherapy (CRT) or radiotherapy (RT) for head-and-neck cancer.Method: Patients completed the EAT-10 four times: (I) Within two weeks of commencing (C)RT, (II) in the final week of (C)RT, (III) two weeks post-(C)RT and (IV) following discharge from speech-language pathology services. Data was compared to their oral intake status, using the Functional Oral Intake Scale (FOIS).Result: Using Cohen's d, changes in the EAT-10 and FOIS were comparable, however, a difference was observed at data-point IV. At data-points I, II and III, the EAT-10 had a strong negative correlation with the FOIS (Spearman's ρ= -0.81, -0.80 and -0.81 resp.). At data-point IV the correlation strength decreased (Spearman's ρ= -0.69). Fisher's Z transformation found no statistically significant correlation coefficient differences between data-points I, II and III. A significant difference in correlation was found between these data-points and data-point IV (p = 0.027; p = 0.039 and p = 0.022 resp.). A very high internal consistency was found (Cronbach's α > 0.95) for all data-points.Conclusion: This study's results indicate that the EAT-10 has weaknesses in the external responsiveness and has redundancy of its question items.

Enhancing adherence to antiretroviral therapy at the HIV clinic in resource constrained countries; the Tanzanian experience.

OBJECTIVE: To evaluate various strategies aimed at improving adherence to antiretroviral therapy (ART). METHODS: Patients initiated on ART at Muhimbili National Hospital HIV clinic were randomly assigned to either regular adherence counseling, regular counseling plus a calendar, or regular counseling and a treatment assistant. Patients were seen monthly; during these meetings self-reported adherence to treatment was recorded. Disease progression was monitored clinically and immunologically. RESULTS: Of the 621 patients randomized, 312 received regular counseling only, 242 regular counseling and calendars, while 67 had treatment assistants in addition to regular counseling. The mean (SD) follow-up time was 14.5 (4.6) months. During follow-up 20 (3.2%) patients died, and 102 (16.4%) were lost to follow-up; this was similar in all groups. In 94.8% of all visits, patients reported to have adhered to treatment. In only 39 (0.7%) visits did patients report a < or = 95% adherence. There were no differences in adherence (P = 0.573) or differences in CD4 count and weight changes over time in the interventions. CONCLUSIONS: Good adherence to ART is possible in resource constrained countries. Persistent adherence counseling in clinic settings by itself may be effective in improving adherence to ART.

CYP3A5 genotype has an impact on the metabolism of the HIV protease inhibitor saquinavir.

CYP3A is the main enzyme subfamily involved in the metabolism of the HIV protease-inhibitor saquinavir. We hypothesized that individuals homozygous for CYP3A5*1 might have a higher oral clearance of saquinavir, compared with subjects lacking functional CYP3A5 alleles. A single-dose pharmacokinetic trial of saquinavir soft gel capsules, 1,200 mg, was performed in 16 black Tanzanian healthy volunteers with two functional CYP3A5 alleles (*1/*1) and in 18 volunteers without functional CYP3A5 alleles (both alleles being either *3, *6, or *7). The median area under the plasma concentration-time curve (AUC)0-24 reached among subjects with two functional alleles was 1,410 ng h/ml (interquartile range (IQR) 826-1,929), whereas it was 2,138 ng h/ml (IQR 1,380-3,331) in subjects without (P=0.0533, Mann-Whitney U-test). The median ratio of saquinavir over its M2 plus M3 hydroxy metabolites in urine was 64 (IQR 52-73) in subjects with two functional alleles, whereas it was 145 (IQR 89-181) in those without (P=0.000078, Mann-Whitney U-test). In conclusion, saquinavir is metabolized by CYP3A5. The median AUC0-24 for saquinavir among individuals with two functional CYP3A5 alleles was 34% lower than among those with no functional alleles. To clarify the clinical importance of the CYP3A5 polymorphism, further studies should be conducted on saquinavir, dosed to steady state, in the presence of ritonavir boosting.

Clinical and echocardiographic study of hypertrophic cardiomyopathy in Tanzania.

There are few published reports of hypertrophic cardiomyopathy (HCM) in Africans, partly due to lack of Echocardiography machines at most hospitals. Among 6680 patients referred for echocardiography at Muhimbili National Hospital between June 1998 and October 2002, 134 (0.19%) patients had HCM. Their mean age was 54.8+/-14.2 years. In total 67.9% were men and 32.1% were women. Due to the diverse clinical features only eight (5.9%) patients had a correct diagnosis of HCM prior to their ECHO. The important role of echocardiography in the diagnosis of HCM is stressed with a plea for the increasing availability of this non-invasive technique for early and accurate diagnosis.

The prevalence and incidence of HIV-1 infection and syphilis in a cohort of police officers in Dar es Salaam, Tanzania: a potential population for HIV vaccine trials.

OBJECTIVES: To assess the suitability of a cohort of police officers in Dar es Salaam for HIV vaccine trials by determining the prevalence and incidence of HIV-1 infection, active syphilis and their associated factors. DESIGN AND SETTING: An open cohort study of police officers in Dar es Salaam, Tanzania. METHODS: Recruitment of police officers began in 1994. A standardized questionnaire was completed at enrolment and subsequent visits. HIV antibodies were determined using two consecutive enzyme-linked immunosorbent assays. Samples repeatedly discordant on the two tests were tested by a Western blot assay. Treponema pallidum antibodies were first determined by Venereal Disease Research Laboratory (VDRL) test and reactive sera were confirmed by Treponema pallidum hemagglutination test. RESULTS: At the end of 1996 a total of 2850 police officers had been recruited of whom 2733 (96%) consented to be tested for HIV. The overall HIV-1 seroprevalence at recruitment was 13.8% (378 of 2733). Females had a significantly higher HIV-1 seroprevalence, 18.0% (55 of 306), as compared to males, 13.3% (323 of 2427), P< 0.05. From a total of 2215 married police officers, 585 (26.4%) responded to a question on extramarital sex within the previous 3 months of whom 36.2% (212 of 585) admitted to have had at least one extramarital sexual intercourse. Condoms were not used during these encounters by 178 of 212 (84.0%). As of 31st December 1998, among the 1524 males observed for 2553 person-years (PYAR), 50 had seroconverted and among 200 females observed for 357 PYAR, eight had seroconverted. The overall crude HIV-1 incidence was thus 19.9/1000 PYAR; 19.6 and 22.4/1000 PYAR for males and females, respectively. The overall prevalence and incidence of active syphilis were 3.1% (88 of 2850) and 8.6/1000 PYAR (26 of 3149), respectively. Males had a higher prevalence of active syphilis, 84 of 2525 (3.3%) than females, five of 325 (1.5%), P = 0.09. CONCLUSIONS: There was high risk sexual practice including low condom use in this cohort of police officers. The incidence and prevalence of HIV infection were high. Police officers in Dar es Salaam are therefore a potential population group for HIV vaccine evaluation.

Case report: renal scintigraphy in the diagnosis of urinary extravasation.

Renal scintigraphy is a sensitive method for disclosing urinary extravasation. Its role following a road traffic accident is clearly presented in this case report. It is concluded that such a study can fill an important gap between the clinical and intravenous urography assessment and the more invasive studies in trauma victims.

Preparation, quality control and application of 99mTc-gluco-ene-diolate for renal scanning.

A one-step freeze-dried Sn-glucose kit was developed to be labelled with technetium-99m. TLC, paper chromatography and gel chromatography column scanning techniques (GCS) were used for the determination of the labelling yield of the complex. High radiochemical purity was obtained (98%). In vivo distribution studies were performed in white rats. Maximum uptake in kidneys (28%) was achieved in 15-90 min. The blood disappearance curve studies of the labelled Sn(II)-gluco-ene-diolate in rabbits have shown two disappearance phases of activity from blood with biological half-times of 10 and 150 min for the fast and slow component respectively.

Investigation of the parameters related to the formation of 99mTc-pyrophosphate complexes using gel chromatography column scanning.

Using gel chromatography two different 99mTc-PPi complexes (complex I and II) were observed under various pH-values. In neutral medium complex II was the main product while in acidic or alkaline media complexes I and II were formed. Our results related to the organ distribution in mice revealed that complex II is a bone-seeking agent whereas complex I concentrates in the kidneys.

The role of bone scintigraphy and other imaging modalities in knee pain.

The role of bone scintigraphy (planar and SPET) in the investigation of chronic knee pain is assessed in conjunction with other imaging modalities. A review of the literature has been undertaken and an imaging strategy suggested. It is concluded that bone scintigraphy has an important role to play as an imaging modality when investigating cases of chronic knee pain.

Imaging modalities and low back pain: the role of bone scintigraphy.

The role of bone scintigraphy, both planar and single photon emission tomography (SPET), in investigating cases of chronic back pain is assessed in conjunction with other imaging modalities. A review of the literature was undertaken and an imaging strategy is suggested. It is concluded that bone scintigraphy has an important role as an imaging modality in investigating cases of chronic low back pain.

A rapid method for the preparation of 99Tcm hexametazime-labelled leucocytes.

99Tcm (+/-)-hexamethylpropyleneamineoxime (HMPAO) (99Tcm Hexametazime) has been recently reported as an alternative for labelling leucocytes. For reasons of convenience, radiation dose and image quality, many workers have welcomed this novel approach except for its complicated labelling protocol and venesection of 100 ml. This technique has been modified to give a simpler routine in-house labelling technique. It has three advantages: only about 20 ml of blood is required, the labelling time is just under 1 h and high yields of labelled leucocytes are obtained (mean of 500 MBq per injection dose). The properties of labelled leucocytes using this modified method are; 80% granulocyte-bound radioactivity, a rapid lung transit and a blood granulocyte recovery of 40% at 30 min similar to those described previously. The viability of the labelled leucocytes was tested and confirmed in vitro using a migration technique and in vivo by showing no lung retention on early imaging and high splenic uptake. A rapid in-process chromatography assessment procedure for regulating the protocol has been developed. Successful abscess imaging by 4 h has been achieved in 21 patients with normal results in another 22 patients without abscesses. This simpler method should encourage a more widespread application of scintigraphy using radiolabelled granulocytes.

Radiolabelled white blood cell imaging in arthritis. Is it a blood pool effect?

The aim of this study is to determine whether white blood cell imaging in inflammatory conditions is due to a blood pool effect as a result of an increased vascularity and vascular permeability, or whether cellular migration is the major contributing factor. It will be shown that white cell uptake is a specific phenomenon in the rheumatoid knee joint and not just a blood pool effect.

A comparative study of labelled neutrophil behaviour in patients with rheumatoid arthritis and normal volunteers.

A comparative study of neutrophil pharmacokinetics and distribution between normal volunteers and patients with rheumatoid arthritis (RA) is presented. White cell viability was confirmed by prominent localization of activity in the spleen with minimal liver uptake and lack of retention in the lungs in both normal volunteers and RA patients. There were no significant differences between both groups in granulocyte clearance from the lungs and their subsequent distribution in the spleen, bone marrow and liver. The results of this study demonstrate that the behaviour of granulocytes in RA patients is essentially unchanged from that of normal volunteers.

The response of 99Tcm-methylene diphosphonate and 99Tcm-hexametazime-labelled neutrophils to intra-articular steroid injection in rheumatoid arthritis.

The synovial and bone uptake of tracer in the knees of patients with rheumatoid arthritis (RA) was quantified using 99Tcm-hexamethyl propylene amine oxime-labelled leucocytes and 99Tcm-methylene diphosphonate (MDP), respectively. Significant neutrophil migration and MDP uptake occurred in the knees of patients with RA irrespective of the disease duration. In all but one patient neutrophil migration was reduced after intra-articular steroid injection. The change in MDP uptake after steroid injection was variable. There was a significant correlation between the percentage reduction in neutrophil migration and pain score, while the latter correlated poorly with the change in MDP uptake. The quantification of the neutrophil component of the inflammatory process is a sensitive index for monitoring RA activity and response to pharmacological interventions, while quantitative bone scintigraphy should not be employed to monitor changes in joint inflammation in patients with RA.

Radioleucoscintigraphy in osteoarthritis. Is there an inflammatory component?

The possible contribution of an inflammatory component in osteoarthritis was investigated. There was no correlation between the percentage uptakes of 99Tcm-hexamethylpropyleneamine oxime (HMPAO)-labelled white blood cells and 99Tcm-methylene diphosphonate (MDP) and between the former and pain scores. A significant correlation was found between the percentage uptake of 99Tcm-MDP and pain scores (0.002 > P > 0.01). In osteoarthritis, 99Tcm-HMPAO-labelled white cell imaging may or may not show a positive localization in the synovial membrane. Positive white cell localization appears to be limited to the area that corresponds to the radiological evidence of the condition and the positive uptake of the skeletal imaging agent.

99Tcm-labelled leucocyte imaging in active rheumatoid arthritis.

A simplified technique of labelling leucocytes with technetium-99m is described and applied to patients with active rheumatoid arthritis. The clinically active and less active knees in seven patients were imaged and the uptake of labelled leucocytes was measured. The measurements were repeated after local steroid injection into nine painful knees. A 50-80% reduction in leucocyte uptake localized to the region of the synovium was demonstrated in the eight knees which showed clinical responses and a rise of 8% in the non-responder. There was a variable response in the knees that were not injected. 99Tcm leucocyte imaging in rheumatoid arthritis is able to assess objectively joint inflammation and its response to treatment.

Echocardiographic profile of endomyocardial fibrosis in Tanzania, East Africa.

OBJECTIVES: To demonstrate and evaluate the usefulness of two dimensional and Doppler echocardiography in the diagnosis of endomyocardial fibrosis (EMF) in countries with poor resources. Also to evaluate the clinical assessment as a predictor of echocardiographically proven EMF. DESIGN: Descriptive hospital based study. SETTING: Muhimbili National Hospital, Dar es Salaam, Tanzania. SUBJECTS: 39 patients (27 male and 12 female, mean age 13.5 years) attending our Cardiac Clinic were investigated to determine the extent to which specific features could be diagnosed by transthoracic echocardiography. MAIN OUTCOME MEASURES: Identifying and characterizing echocardiographic features specific for diagnosing EMF non-invasively. RESULTS: Only eight (21%) patients had a correct clinical diagnosis, leaving 79% of the patients at risk of being misdiagnosed and hence wrongly receiving expensive treatment. The majority of the patients (69.2%) presented with signs of elevated systemic venous pressure due to right ventricular EMF. CONCLUSION: We have demonstrated that echocardiography remains a fundamental investigation in the least developed countries in achieving the correct diagnosis.

Stroke subtypes in Black Tanzanians: a retrospective study of computerized tomography scan diagnoses at Muhimbili National Hospital, Dar es Salaam.

Limited data are available on the stroke subtypes in Tanzania and sub-Saharan Africa. The present study was aimed at determining retrospectively the pattern of confirmed strokes in all patients in our hospital who had been given a computerized tomography (CT) brain scan during the study period (April 2001 to May 2002). Over the 12-month period 371 CT brain scans were taken, of which 148 showed stroke, 89 (60.1%) showed haemorrhage and 59 (39.9%) showed infarcts (P<0.05). Among the haemorrhagic group 48 (53.9%) were men and 41 (46.1%) women, while 31 (52.5%) men and 28 (47.5%) women had infarction. We concluded that there were relatively more cases of cerebral haemorrhage than infarction. Hypertension and diabetes mellitus were common risk factors in both subtypes of stroke.

Effect of rifampicin and CYP2B6 genotype on long-term efavirenz autoinduction and plasma exposure in HIV patients with or without tuberculosis.

We performed a prospective comparative study to examine, from a pharmacogenetics perspective, the effect of rifampicin (RIF) on long-term efavirenz (EFV) autoinduction and kinetics. In a study population of patients with HIV receiving EFV with RIF (arm 2, n = 54) or without RIF (arm 1, n = 128 controls), intraindividual and interindividual plasma EFV and 8-hydroxyefavirenz levels were compared at weeks 4 and 16 of EFV therapy. In arm 2, RIF was initiated 4 weeks before starting EFV. In controls (arm 1), the plasma EFV was significantly lower whereas 8-hydroxyefavirenz was higher at week 16 as compared to week 4. By contrast, there were no significant differences in plasma EFV and 8-hydroxyefavirenz concentrations over time in arm 2. At week 4, the plasma EFV concentration was significantly lower in arm 2 as compared to arm 1, but no significant differences were observed by week 16. When stratified by CYP2B6 genotype, significant differences were observed only with respect to CYP2B6*1/*1 genotypes. Ours is the first report of the CYP2B6 genotype-dependent effect of RIF on long-term EFV autoinduction.