Modification to improve efficiency of sampling schedules for BA/BE testing of FDC anti-tuberculosis drugs.

SETTING: The assessment of rifampicin (RMP) containing fixed-dose combination (FDC) formulations using in vivo bioequivalence testing is widely accepted. It would be advantageous for both the drug regulatory authorities and drug manufacturers, for optimum minimum blood testing time intervals that encompass all anti-tuberculosis active constituents in the FDC to be established. OBJECTIVE: To determine the optimum blood sampling schedule for testing novel FDC anti-tuberculosis drugs, isoniazid, RMP, pyrazinamide and ethambutol DESIGN: The results of 12 different single-dose, two-way cross-over designs are presented. The studies determined the bioavailability and bioequivalence of RMP-containing FDCs, and conformed with the requirements of the South African national drug regulatory authority for each of the active constituents. RESULTS: The pharmacokinetic parameters to determine bioavailability and the Hauschke method to determine bioequivalence revealed that a six-point time protocol, namely 0, 1, 2, 4, 6 and 8 h, provides a good approximation of the area under the curve, and that an 11-point time protocol of 0, 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6 and 8 h provided information comparable to the conventional 15 time-points for FDCs containing up to four drugs. CONCLUSION: The findings provide concrete economic benefit and convenience for quality assurance testing of existing and novel FDCs.

Efficacy of rectal artesunate compared with parenteral quinine in initial treatment of moderately severe malaria in African children and adults: a randomised study.

BACKGROUND: Many patients with malaria of increasing severity cannot take medicines orally, and delay in injectable treatment can be fatal. We aimed to assess the reliability of absorption, antimalarial efficacy, and tolerability of a single rectal dose of artesunate in the initial management of moderately severe falciparum malaria. METHODS: 109 children and 35 adults were randomly assigned to rectal artesunate (single dose of about 10 mg/kg) or parenteral quinine treatment (10 mg/kg at 0, 4, and 12 h). The primary endpoint was the proportion of patients with peripheral asexual parasitaemia of less than 60% of that at baseline after 12 h. Secondary endpoints were clinical response and concentrations of drug in plasma. Analysis was by intention-to-treat. FINDINGS: All artesunate-treated patients had pharmacodynamic or pharmacokinetic evidence of adequate drug absorption. 80 (92%) of 87 artesunate-treated children had a 12 h parasite density lower than 60% of baseline, compared with three of 22 (14%) receiving quinine (relative risk 0.09 [95% CI 0.04-0.19]; p<0.0001). In adults, parasitaemia at 12 h was lower than 60% of baseline in 26 (96%) of 27 receiving artesunate, compared with three (38%) of eight receiving quinine (relative risk 0.06 [0.01-0.44]; p=0.0009). These differences were greater at 24 h. Clinical response was equivalent with rectal artesunate and parenteral quinine. INTERPRETATION: A single rectal dose of artesunate is associated with rapid reduction in parasite density in adults and children with moderately severe malaria, within the initial 24 h of treatment. This option is useful for initiation of treatment in patients unable to take oral medication, particularly where parenteral treatment is unavailable.

In vitro interactions of Aspilia africana (Pers.) C.D. Adams, a traditional antimalarial medicinal plant, with artemisinin against Plasmodium falciparum.

Traditional antimalarial medicinal preparations are widely used concurrently with antimalarial drugs in malaria endemic areas. The plant Aspilia africana (Pers.) C.D. Adams is commonly used for traditional treatment of malaria symptoms in East and Central Africa. An in vitro study of interactions between an extract from this plant with artemisinin against two strains of Plasmodium falciparum showed an antagonist relationship against both the chloroquine-sensitive D10 and the chloroquine- and sulphonamide-resistant K1 strains of Plasmodium falciparum. The extract reduced accumulation of radiolabelled dihydroartemisinin ((3)H-DHA) by erythrocytes infected with the chloroquine- and sulphonamide-resistant K1 strain of Plasmodium falciparum while it increased its accumulation by erythrocytes infected with the chloroquine-sensitive D10 strain. These results suggest complex interactions between the antimalarial medicinal plant and artemisinin. This study also proposes an in vitro approach to investigating interactions between antimalarial drugs and traditional medicines.

The in vitro and in vivo antimalarial activity of Cardiospermum halicacabum L. and Momordica foetida Schumch. Et Thonn.

Two plants Cardiospermum halicacabum L. and Momordica foetida Schumch. Et Thonn traditionally used to treat symptoms of malaria in parts of East and Central Africa were screened for in vitro and in vivo antimalarial activity. Using the nitro tetrazolium blue-based parasite lactate dehydrogenase assay as used by [Makler, M.T., Ries, J.M., Williams, J.A., Bancroft, J.E., Piper, R.C., Gibbins, B.L., Hinrichs, D.J., 1993. Parasite lactate dehydrogenase as an assay for Plasmodium falciparum drug sensitivity. American Journal of Tropical Medicine and Hygiene 48, 739-741], water extracts from the two plants were found to have weak in vitro antiplasmodial activity with 50% inhibitory concentrations (IC50s) greater than 28.00 microg/ml. In vivo studies of water extracts from the two plants showed that Momordica foetida given orally in the dose range 10, 100, 200 and 500 mg/kg twice daily prolonged survival of Plasmodium berghei (Anka) infected mice from 7.0+/-1.8 to 17.9+/-1.8 days. The water extract of Cardiospermum halicacabum L was toxic to mice, none surviving beyond day 4 of oral administration, with no evidence of protection against Plasmodium berghei malaria. The study emphasizes the discrepancy that might be found between in vitro and in vivo testing of plant-derived antimalarial extracts and the need to consider in vitro antiplasmodial data with this in mind. Further studies on Momordica foetida as a source of an antimalarial remedy are indicated on the basis of these results.

Erythropoietin production in anemia associated with experimental cancer.

Serum erythropoietin (EPO) concentrations reportedly are depressed in patients with chronic disorders such as cancer, rheumatoid arthritis, and acquired immunodeficiency syndrome. We evaluated serum EPO levels in mice with tumors and found that the EPO response was appropriate for the associated anemia during the major part of the disease process. The levels of the hormone increased as the anemia worsened in association with progression of the disease. The increased EPO levels were comparable to those of controls with a similar degree of experimentally induced anemia. Only during the terminal stages of cancer, when the animals were severely cachectic, were serum EPO concentrations lower than in controls with a similar degree of anemia. These findings suggest that a blunted EPO response in experimental cancer occurs only in association with advanced disease.

Role for the plasmodium falciparum digestive vacuole in chloroquine resistance.

We have developed a method for the isolation of pure and intact Plasmodium falciparum digestive vacuoles capable of ATP-dependent chloroquine (CQ) accumulation in vitro. The method is rapid and reliable, and it produces a high yield of vacuoles (20%). CQ accumulation in isolated vacuoles was found to be ATP-, Mg2+-, and temperature-dependent. We then investigated the CQ-accumulating capabilities of vacuoles isolated from CQ-resistant (CQR) and CQ-sensitive (CQS) parasites. At external CQ concentrations of 100 and 250 nM, vacuoles isolated from two CQS strains (D10 and RSA3) (Vm: 380-424 fmol/10(6) vacuoles/hr) accumulated significantly more CQ (approximately 3 times) than those isolated from three (FAC8, RSA11, and RSA15) of the four CQ-resistant strains of P. falciparum tested (Vmax: 127-156 fmol/10(6) vacuoles/hr) (P < or = 0.05). We propose that the low level of CQ accumulation observed in vacuoles isolated from most of the CQ-resistant parasites tested contributes to the decreased CQ accumulation seen in these strains and, hence, to CQ resistance. Although it is often suggested that the digestive vacuole of the P. falciparum parasite is involved in the mechanism of CQ resistance, to our knowledge this is the first direct confirmation.

Drug regulation in South Africa.

South Africa has a population of approximately 30 million people. The country has a mixture of advanced industrial and rural economies, but the medicine control system is consistent with similar systems established in the major industrial countries of Western Europe and North America. Because most of South Africa's population lives in conditions more closely akin to the developing world than to the Western nations, it is important to examine whether the country is optimally served by this drug regulation model and to define critically the strengths and limitations of the established system. The conclusions might be relevant for other countries at a comparable stage of development.

An economic comparison of chloroquine and sulfadoxine-pyrimethamine as first-line treatment for malaria in South Africa: development of a model for estimating recurrent direct costs.

The relative cost-effectiveness of chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) as first-line antimalarial therapy in southern Africa is of great interest to policymakers, clinicians and researchers in the subregion. A model was developed to access the cost-effectiveness of replacing CQ with SP as first-line treatment in Mpumalanga, South Africa, where malaria is seasonal and the population is non-immune. In-vivo drug resistance levels were used to derive a 'resistance variable' for each drug, which was used to compare the costs to the public healthcare provider associated with either therapeutic option. Costs including drugs, staff time, transport, maintenance, utilities, training and consumables were determined and subjected to Monte Carlo simulation and subsequent analysis to generate an average cost-effectiveness ratio (ACER) with confidence intervals for each drug. SP was found to be 4.8 (95% CI 3.3-6.7) times more cost-effective than CQ in Mpumalanga at 1997 resistance levels and costs, despite the far greater cost per treatment course of SP (US$ 4.02 as opposed to US$ 0.22 for CQ) in South Africa. At the price of SP in Kenya and Uganda (US$ 0.47-4.80 per treatment course), the ACER for SP does not change materially, increasing to between 5.1 and 5.6. Resistance emerged as the factor that most influenced the ACER of a specific drug. Indirect costs, compliance, changes in effectiveness and costs over time and costs of adverse events were not included in the model owing to paucity of data and logistical difficulties. Since most of these are likely to be similar in both drug models, the relative ACER is unlikely to be significantly altered by their inclusion.

The effect of artesunate combined with standard antimalarials against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum in vitro.

The interactions of artesunate with chloroquine, mefloquine, quinine, doxycycline and pyrimethamine were tested in vitro against chloroquine-sensitive (D10) and chloroquine-resistant (RSA11) strains of Plasmodium falciparum. Mefloquine and quinine both showed synergism of artesunate activity against each of the strains, whilst doxycycline showed an additive interaction. Pyrimethamine combinations were antagonistic, and the combination of artesunate with chloroquine was antagonistic against RSA11, and additive against D10. Although weak antagonism in vitro might not indicate any clinical significance, synergism with artesunate may increase the clinical usefulness of either drug, and could potentially be of value in delaying the emergence of resistance.

Evidence for an active immune response in acute hyperthyroidism (Graves' disease).

Activated lymphocytes, identified by an autoradiographic labeling method, were found to be present in the peripheral blood of the majority of 20 patients with acute hyperthyroidism (Graves' disease). The number of such cells in the blood was significantly greater than that found in 30 healthy controls (p less than 0.00001), and in 13 patients who had previously suffered from acute hyperthyroidism, and who were judged to be euthyroid following therapy (p less than 0.025). This latter group included two patients in whom such activated lymphocytes had been found in the blood during the acute phase of their illness. Furthermore, there were significant differences between the number of such activated circulating lymphocytes in the group of patients with acute hyperthyroidism and five patients suffering from hyperthyroidism due to a toxic thyroid nodule (p less than 0.001), five patients suffering from primary myxedema (p less than 0.001), or in 14 patients with a nontoxic multinodular goiter (p less than 0.05). Identification and counting of circulating T and B lymphocytes by fluorescent immunolabeling and rosette-forming techniques in a small number of the patients with acute hyperthyroidism failed to reveal significant differences from the normal. The results suggest that in acute hyperthyroidism there is active stimulation of the cellular immune system, and that this effect is specific to the early, untreated phase of the disease. This response is different to other thyroid diseases, including hyperthyroidism due to a toxic thyroid nodule.

Cytokine-mediated inhibition of erythropoietin synthesis by dexamethasone.

The effect of inflammatory cytokines on the in-vitro synthesis of erythropoietin by HepG2 cells was evaluated. Monocyte-conditioned medium, and the cytokines interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha all reduced synthesis of erythropoietin. The steroidal anti-inflammatory drug, dexamethasone, did not affect cytokine-mediated erythropoietin inhibition. Dexamethasone did cause a reduction in the secretion of erythropoietin inhibitory cytokines from monocytes. These results point to a possible therapeutic approach in the treatment of anaemia caused by suppression of erythropoietin synthesis by monocytic cytokines.

The role of oxygen free radicals in isoniazid-induced hepatotoxicity.

Isoniazid and its metabolites acetylisoniazid, hydrazine and monoacetylhydrazine were investigated for generation of oxygen free radicals during incubation with rat liver slices. Lipid peroxidation was assessed by the thiobarbituric acid reactive substances test using malonaldehyde as the external standard, while hepatotoxicity was assessed by histopathology studies. Malonaldehyde formed in liver slices after 10 hours of incubation with the drugs was 1.28 +/- 0.24 nmol/mg for isoniazid (control 1.12 +/- 0.17 nmol/mg); 0.88 +/- 0.45 nmol/mg for acetylisoniazid (control 0.84 +/- 0.42 nmol/mg); 1.43 +/- 0.14 nmol/mg for monoacetylhydrazine (control 1.10 +/- 0.12 nmol/mg) and 1.36 +/- 0.02 nmol/mg for hydrazine (control 1.13 +/- 0.04 nmol/mg). Histologically, all slices exhibited hepatic necrosis by 4 hours. However, hydrazine-induced hepatotoxicity was characterized by nuclear hyperchromatsia, karyolysis and karyohexis while monoacetylhydrazine exhibited hydropic karyomegaly only. Isoniazid and acetylisoniazid cytotoxicity exhibited a mixture of the above features such that it could be attributed to the two metabolites, hydrazine and monoacetylhydrazine. In conclusion, there was no evidence implicating oxygen free radicals in isoniazid-induced hepatotoxicity; however, the histopathology findings indicate a need for a review of our knowledge on pathognomonic features of isoniazid hepatotoxicity.

Oxidative stress during antituberculous therapy in young and elderly patients.

Using allantoin (ATN) as a marker for reactive oxygen species (ROS), oxidative stress during antituberculous (anti-TB) therapy was compared in 10 young and 9 elderly patients. Before treatment, ATN plasma concentrations in patients were similar to that of volunteers. Administration of a combination of isoniazid (INH), rifampicin (RIF) and pyrazinamide (PZA) increased plasma ATN in both groups of patients. ATN concentrations (M +/- SE) at six hours were higher (P < 0.05) in elderly than in young patients on day one, 8.22 +/- 1.50 vs 1.89 +/- 0.98 microgram/mL); day 30, (5.85 +/- 0.82 vs 0.87 +/- 0.57 microgram/mL; and day 90, (4.84 +/- 1.24 vs 0.52 +/- 0.50 microgram/mL). Because total amount of ATN excreted was similar in both groups on the three occasions, more ATN was formed in elderly than young patients. In conclusion, there was more oxidative stress in elderly than young patients. It is thereby suggested that Anti-TB drugs induce formation of ROS and elderly patients are at a greater risk of toxicity probably because of poor antioxidant mechanisms.

The registration and control of medicines in South Africa: legal issues.

In the provision of health care medicines occupy a central position, both at primary and more advanced levels. Sound medicines have the capability to control and prevent common diseases, and to alleviate suffering. People's confidence in the health services that are provided by the state and by the private sector (as the case may be) is influenced by their knowledge that the medicines that they receive are of good quality and proven efficacy and safety, and that they are continuously available at reasonable cost. A sound national policy for the provision of safe and cost-effective medicines needs to be based on several elements. The most important are: A sound pharmaceutical industry that is able to function in an atmosphere of confidence, with the knowledge that its efforts in support of the public health are understood and respected; and a drug regulatory authority that is trusted for its expertise, independence and integrity. This is as true for a country such as South Africa as it is for a fully industrialised country such as the United States. The regulation and control of medicines in South Africa falls under the aegis of the Medicines Control Council, a statutory body established in accordance with the Medicines and Related Substances Act. In terms of the Act, the council has the mandate to ensure that the medicines available to the South African public are safe, effective, and of high quality, and that their availability is in the public interest. In considering this, the council may take into account only the scientific data available.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics of ranitidine in patients with chronic duodenal ulceration.

We have studied the pharmacokinetics of ranitidine, a new H2-receptor blocker in 6 male patients suffering from chronic duodenal ulceration. In 5 patients single-dose kinetics were determined over a 24-hour period following 150 mg of ranitidine given orally and steady state kinetics were examined after treatment for 28 days with 150 mg ranitidine given twice daily. At this stage all 5 patients showed endoscopic evidence of ulcer healing. Our findings showed little inter-individual variation in elimination half-life, peak level, trough level and area under the curve (AUC). Significant differences were found between single dose and steady state situations with respect to the elimination half-life (p less than 0.01), peak levels (p less than 0.01) and area under the curve (p less than 0.05), and no differences in trough levels. The higher peak levels and larger AUC indicate increased bioavailability in steady state. The elimination half-life was shorter in steady state. The steady state kinetics of the sixth patient, a male aged 54 years, with a history of alcohol abuse and chronic duodenal ulceration who had failed to respond symptomatically to treatment with 150 mg ranitidine given twice daily for 8 weeks showed a reduction of peak level and AUC, both of which were corrected over 2 weeks by doubling the daily dose of ranitidine. The initial failure of response of this patient was likely to have been due to pharmacokinetic factors.

The comparative efficacy and safety of aminoglycoside antibiotics.

In this article a report submitted to the Director of Hospital Services of the Cape Provincial Administration is summarized. The object of the report was to make firm recommendations where possible as to the use of the aminoglycosides in the Cape hospitals, taking into account considerations of comparative efficacy, safety and cost.

An assessment of the effects of cyclophosphamide and sodium valproate on the viability of preimplantation mouse embryos using the fluorescein diacetate test.

The fluorescein diacetate test is a measure of both esterase enzyme activity and membrane integrity and it has been shown to be useful in assessing the viability of a variety of cells cultured in vitro, mouse embryos after freezing and thawing, and mouse embryos grown under inadequate culture conditions. In this study, the effects were examined of cyclophosphamide and sodium valproate administered respectively to pregnant inbred CBA mice 60 h after fertilization, on the viability of 84-h blastocysts. Cyclophosphamide 20 and 40 mg/kg bodyweight and sodium valproate 90 mg/kg significantly increased the number of nonviable blastocysts. Cyclophosphamide 4 mg/kg and sodium valproate 23 and 45 mg/kg did not adversely affect blastocyst viability. The intensity of embryo fluorescence correlated well with the subsequent development of the embryos in culture (r = 0.863; p less than 0.001). The test had a sensitivity of 83% and a specificity of 100%. Exposure of embryos to fluorescein diacetate under the conditions of this experiment did not adversely influence the subsequent postimplantation development of 84-h blastocysts cultured in vitro for a further 120 h. These findings suggest that the fluorescein diacetate test is a simple, rapid, and nontoxic procedure that may be useful in assessing the viability of preimplantation embryos after exposure to embryotoxic drugs and chemicals.