Identification of novel erythromycin derivatives in mother liquor concentrates of Streptomyces erythraeus.

The identification of five novel compounds, pseudo-erythromycin A-6,9-hemiketal, 8,9-anhydro-pseudo-erythromycin A-6,9-hemiketal, 8,9-anhydro-pseudo-N-demethylerythromycin A-6,9-hemiketal, 5-O-beta-D-desosaminylerythronolide A and 15-nor-erythromycin C, in mother liquor concentrates of Streptomyces erythraeus is described. The pseudo-erythromycin derivatives are characterized by a 12-membered macrocyclic ring as a result of C13----C11 trans-lactonization. The five compounds have very little antimicrobial activity.

Evaluation of tetracycline raw materials and finished products found on the Kenyan market.

Contents of tetracycline, its degradation products (epitetracycline, epianhydrotetracycline, anhydrotetracycline) and a fermentation impurity (2-acetyl-2-decarboxamidotetracycline) were determined in four raw materials, 12 batches of six ointment products, four eye ointment products and nine batches of five capsule products, all sampled from the Kenyan market. The analytical method was liquid chromatography on a column packed with a poly(styrenedivinyl-benzene) material (8-microns PLRP-S 100 A). All raw materials and finished products had tetracycline contents and impurity levels within the prescribed compendial limits.

Antimalarial activity of Ajuga remota Benth (Labiatae) and Caesalpinia volkensii Harms (Caesalpiniaceae): in vitro confirmation of ethnopharmacological use.

Field trips to herbalists' practices in an area about 200 miles around Nairobi (Kenya) enabled us to make a list of medicinal plant species preferentially used to treat malaria. Ajuga remota and Caesalpinia volkensii were further investigated as being the most frequently used species. Aqueous decoctions, ethanol macerates, and petroleum ether, methanol and water Soxhlet extracts of these plants were further tested for their in vitro antimalarial properties in a chloroquine sensitive (FCA/20GHA) and resistant (W2) strain of Plasmodium falciparum. The activity was assessed by the parasite lactate dehydrogenase (pLDH) assay method. There was a concentration-dependent inhibition by the vegetal extracts of both plants. The IC(50) of the most active A. remota extract (ethanol macerate) was 55 and 57 microg/ml against FCA/20GHA and W2, respectively. For C. volkensii, it was the Soxhlet-water extract which was most active against FCA/20GHA with an IC(50) of 404 microg/ml while the petroleum ether extract exhibited the most activity against W2 with an IC(50) of 250 microg/ml. Further phytochemical work is being done in order to identify the active principles.

In vitro evaluation of carbamazepine 200 mg tablets.

A comparative in-vitro performance of carbamazepine 200mg tablet products available on the Kenyan market was evaluated. The products which include the innovator product, Tegretol, have similar quality consonant with pharmacopoeial specifications. A batch of one of the products had a carbamazepine content of 106.6% label claim which was outside the upper limits of 105%. One product packaged in multiple-unit containers of a 1000, had an unacceptable high friability of 6.82% loss in weight. All products had good dissolution profiles and released at least 70% of the dose within 45 minutes. Drug dissolution from tablets was found to vary between batches for one product. At each sampling time, most generics had wide variations in amount of dissolved drug. The effect of such variations on tablet efficacy cannot be ascertained in the absence of bioavailability data.

Quality performance of metronidazole tablet products on the Kenyan market.

The in vitro performance of metronidazole tablet products by different manufacturers available on the Kenyan market was evaluated. It was found that a number of generic metronidazole tablet products have quality performance equal to that of Flagyl--the innovator product. All products confirmed to pharmacopoeial specifications. Three products with percent weight loss of 1.4, 11.08 and 14.93 failed the crucial friability test, for multidose packs. Two products failed the dissolution test releasing 46.8% and 45.8% of drug in 40 minutes. Drug release from tablet was found to vary between batches for one product. Ageing appears to decrease amount of drug released from tablets but longer storage periods and more samples are required before definite conclusions are drawn.

The neutralizing capacity and sodium content of antacid brands on the Kenyan market.

Seventeen brands of antacid products available on the Kenya market were investigated for their acid neutralising capacity and sodium content. Thirteen tablet products gave neutralising capacity per tablet of between 4.7 to 14.12 mMol hydrochloric acid. The neutralising capacities for the suspensions ranged between 11.97 to 34.32 mMol hydrochloric acid for 10ml suspension. The lowest neutralising capacities were obtained for products based on compound magnesium trisilicate and higher capacities for those containing magaldrate, or magnesium hydroxide or magnesium carbonate in combination with other ingredients. The fastest rate of neutralization was obtained with preparations containing carbonates and the lowest by compound magnesium trisilicate. The sodium content for the preparations was between < 0.001 mEq to 0.732 mEq sodium per minimum recommended dose. The study shows a high degree of variation in both the acid neutralising capacities and the sodium content of the different brands investigated.

Comparative bioavailability of two brands of chlorpropamide in Kenyans.

The relative bioavailability of two brands of chlorpropamide, Dibonis, and Diabinese has been evaluated in four healthy male volunteers in a randomized, balanced, cross-over study. No statistically significant differences were observed in the absorption rate constant, ka, time to reach peak serum concentration, tp, maximum serum concentration, Cmax, the overall elimination rate constant, kel, and the area under the curve, AUC, at 95% confidence level.

Drug quality control work in Daru: observations during 1983-1986.

During a 4 year period (January 1983 to December 1986), 418 requests for drug analysis were received in the Drug Analysis and Research Unit, Department of Pharmacy, University of Nairobi. Of these requests, 212 were from Medical Supplies Coordination Unit, 190 from Government hospitals and health research institutions, 11 from the Ministry of Health Headquarters (Director of Medical Services and Chief Pharmacist) and 5 came from local pharmaceutical manufacturers. Of the samples analysed, 70.8% were from local manufacturers, 26.1% were imported and 3.1% were from undeclared sources. Failure to comply with test for quality, as set out in official compendia (B.P. Eur. ph. Ip, etc.) were observed at 45.8% for locally manufactured drugs and 31.4% for imported drug products.

Influence of manufacturing practices on quality of pharmaceutical products manufactured in Kenya.

OBJECTIVE: To establish the quality of pharmaceutical products manufactured by the respective industries in Kenya and determine the effect of manufacturing practices on the quality of these products. DESIGN: Cross-sectional study. SETTING: Industries examined are in Nairobi, Kenya. Laboratory analysis was carried out using available facilities at Kenya Medical Research Institute and University of Nairobi, Faculty of Pharmacy. INTERVENTIONS: Structured Questionnaires were administered to examine how the code of good manufacturing practices has been used in the production of each pharmaceutical product by respective companies. Questionnaires designed to evaluate the distribution and carry out limited post-market surveillance study were administered to community pharmacy outlets. Drugs were sampled and analyzed for their quality according to the respective monographs. MAIN OUTCOME MEASURES: The questionnaires administered to the industry included the source of raw materials, quarantine procedure before and after manufacture, manufacturing procedure, quality audit, quality assurance procedure, equipment, and staff. That administered to the pharmacy outlet included availability, affordability and acceptability of locally manufactured pharmaceutical products. Quality analysis of products involved the establishment of the chemical content, dissolution profile, friability, uniformity of weight and identity. For antibiotic suspensions the stability after reconstitution was also determined. RESULTS: There were 15 respondents and two non-respondents from the industry and six out of nine respondents from the pharmacy outlets. The ratio of qualified staff to product range produced seemed to influence product quality. Industries producing several products with only limited number of pharmaceutical staff had more products failing to comply with pharmacopoeia specifications compared to those producing only few products. Nevertheless, all companies are well equipped with quality control equipment, in accordance with type of product manufactured. Private pharmacies stocked few of the locally manufactured products. The reason, they said, was due to low doctor and/or patient acceptance. Compliance with quality specifications as set out in respective monographs was overall 76%. CONCLUSION: Although the local pharmaceutical industries have adopted good manufacturing practices leading to many good quality products currently in commerce, these manufacturing practices are not comprehensive and measures need to be taken to continue improving them.

The microbial and physical quality of recycled gloves.

Plastic surgical gloves reprocessed at the Kenyatta National Hospital (KNH) were tested for microbiological and physical quality, using standard, disposable, factory sterilised surgical gloves as reference. The microbiological tests were carried out using slightly modified British Pharmacopoeia method. The tests to check on the physical integrity of the gloves were designed in our laboratories. A total of 48 pairs of each group were tested. 41.67% of the reprocessed gloves and 12.5% of the reference glove failed sterility test, whereas 47.9% of the former and 0% of the latter had physical defects. These results show significant difference in the microbiological and physical quality of the reprocessed and reference gloves. The reprocessing of plastic surgical gloves is therefore, potentially dangerous and it is strongly recommended that it is discontinued at all levels of health-care institutions.

Steady-state anticonvulsant drug levels in epileptic patients.

Steady state concentrations of three anticonvulsant drugs (phenobarbitone, phenytoin and carbamazepine) were measured in plasma samples from fifteen patients (eight males and seven females; ages: 13-49 years; body weights: 44-70 kg), attending the outpatient Neurology Clinic at Kenyatta National Hospital. In addition, total protein and albumin levels were measured in plasma from patients taking phenytoin. Total protein levels were normal (range: 6.3-7.6 g/dl) in all patients except in one patient (10.7 g/dl). Albumin levels were also normal (range: 3.7-4.1 g/dl) in all patients except one (25.4 g/dl). One patient on phenobarbitone and three patients on phenytoin had no detectable drug levels in their plasma. In the remainder, phenobarbitone, phenytoin and carbamazepine steady state concentrations were 8.7-21.1 mg/L (N = 8), 9.3-27.3 mg/L (N = 6) and 10-19.7 mg/L (N = 5), respectively. The unbound fraction of phenytoin in plasma (fu) was normal(approximately 0.1) in six patients, but relatively high (0.2) in one patient. Most patients in the study complied with the prescribed treatment and their epilepsy was controlled. Cases where drug levels were undetectable probably arose from a lack of money to purchase all prescribed medicines rather than deliberate non-compliance. Routine monitoring of anticonvulsant drug levels may improve management of epileptic patients.

Quality of intravenous infusion fluids manufactured in Kenya.

The incidence and nature of microbial contamination of intravenous fluids prepared by four manufacturing establishments in Kenya was evaluated using the European Pharmacopoeia membrane filtration method for sterility testing. The percentage failures were 28.6% for source D, 18.8% for source A, 12.5% for source B and 10.5% for source C. The major contaminant was aspergillus which was isolated from samples from three sources. Candida and Staphylococcus accounted for the contamination of samples from two sources. Failure rates due to the chemical composition of the products was 66.7% for Source A, 60.0% for D, 41.7% for C and 13.3% for B. The experience of the manufacturing sites appeared to correlate with the quality of the products, with the older manufacturing establishments showing lower percentage failures.

A comparative bioavailability of four Carbamazepine tablet formulations available in the Kenyan market.

The relative bioavailabilities of three carbamazepine tablet formulations available in the Kenyan market (Temporal(R), Taver(R) and Carbamazepine Lincoln) compared with the innovator formulation (Tegretol(R)) were evaluated in seven healthy African volunteers (5 males, two females; aged 22-36 years), according to a randomised fourway crossover study design, following oral administration of single 200 mg doses with a three week washout period. In vitro dissolution profiles of the tablets were also evaluated. Relative bioavailabilities ((F)rel) of Temporal(R), Taver(R) and Carbamazepine Linocoln were 101.2%, 82.2% and 71.6% respectively, compared with Tegretol(R). Percent drug content dissolved in vitro after I hour were 91.3%, 75.9% and 39.3% for Temporal(R), Taver(R) and Carbamazepine Lincoln, respectively. It was concluded that Temporal(R) was bioequivalent to Tegretol(R) while Taver(R) and Carbamazepin Lincoln were bioinequivalent to Tegretol(R). Administration of Taver(R) or Carbamazepine Lincoln might lead to poor control of epileptic seizures.

Tissue distribution and excretion of radioactively labelled compounds in the Wistar rat after administration of [N-methyl-14C]-erythromycin A.

Tissue distribution and excretion of radioactively labelled compounds was studied in the Wistar rat after i.v. administration of [N-methyl-14C]-erythromycin A. Whole-body autoradiography and liquid scintillation counting was used to investigate the tissue localization of radioactivity in pregnant and non-pregnant rats. Tissue levels were maximal within 20 min, except for lachrymal glands, thymus and brain. Large amounts of radioactively labelled compounds, partly originating from active secretion, were present in the small intestine and caecum. Marked concentration of radioactively labelled compounds was also observed in the liver, spleen, lachrymal and salivary glands, lymph nodes, mammary glands, skin, bone marrow, and, to a lesser extent, in the lung, kidney and skeletal muscle. During six hours of experimental follow-up, plasma levels remained lower than corresponding tissue levels. At 1 h the radioactivity in fetuses was about three times lower than that in maternal blood. Within 48 h, more than 90% of the administered radioactivity was excreted. The amounts of radioactivity recovered in urine, faeces and expired air were about 19%, 48% and 24% respectively. After 48 h, 8% of the administered radioactivity was found in the carcass.

Separation of erythromycin and related substances by high-performance liquid chromatography on poly(styrene-divinylbenzene) packing materials.

A comparative evaluation of three brands of poly(styrene-divinylbenzene) copolymers, Hamilton PRP-1 (10 micron), Rogel (8 micron) and TSK-Gel (10 micron), as column packing materials for high-performance liquid chromatographic separation of erythromycins is presented. Erythromycins A, B and C, anhydroerythromycin A, erythromycin A enol ether, N-demethylerythromycin A, anhydro N-demethylerythromycin A and N-demethylerythromycin A enol ether were chromatographed. The effects of column temperature, concentration of organic modifier in the mobile phase, concentration of phosphate buffer, the addition of quaternary ammonium salts and pH are described. The best separations were obtained on TSK-Gel with the mobile phase acetonitrile-methanol-0.2 M tetramethylammonium hydroxide pH 8.0-0.2 M phosphate buffer pH 8.0-water (30:15:25:5:25). PRP-1 and Rogel gave equally good separations but with higher retention volumes.

Optimization of the separation of erythromycin and related substances by high-performance liquid chromatography.

An improved high-performance liquid chromatographic method for analysis of erythromycin is described. The separation can be performed under mild conditions of pH (6.5) and temperature (35 degrees C) on C8 and C18 silica-based reversed-phase materials of different origins. The mobile phase, with a flow-rate of 1.5 ml/min, contained various amounts of acetonitrile (25-40%, v/v), 5% (v/v) 0.2 M ammonium phosphate buffer pH 6.5, 20% (v/v) 0.2 M tetramethylammonium phosphate and water. UV detection at 215 nm allows quantitation of erythromycins A, B and C, N-demethylerythromycin A, erythromycin A enol ether and anhydroerythromycin A. The column history plays a major role, older columns often giving better separations.

Thin-layer chromatographic study of the metabolites of erythromycins in the Wistar rat.

The metabolites of erythromycin A, anhydroerythromycin A, N-demethylerythromycin A and erythromycin B in the Wistar rat were studied by thin-layer chromatography. In some experiments germ-free rats, rats with a cannulated bile duct and a gastrectomized rat were used. The erythromycins examined were shown to undergo two principal changes, N-demethylation and acid-catalysed degradation. It was demonstrated that the stomach and the liver are not the sole sites of acid degradation and demethylation of erythromycins, respectively. Erythromycin A gives three principal metabolites, anhydroerythromycin A, anhydro-N-demethylerythromycin A and N-demethylerythromycin A, and erythromycin A enol ether and N-demethylerythromycin A enol ether are present to a minor extent. 5-O-Desosaminylerythronolide A was also identified, suggesting the presence of an erythromycin glycosidase.

Antibacterial activities of erythromycins A, B, C, and D and some of their derivatives.

The MICs of erythromycins A, B, C, and D and some of their derivatives were determined against 21 gram-positive and 15 gram-negative microorganisms. Antibacterial activity was confined to gram-positive and very few gram-negative bacteria. Erythromycin B was somewhat less active than erythromycin A, and erythromycin C and D showed about half that activity or even less. Most other derivatives had negligible activity. Determination of potency by diffusion and turbidimetric assays were in line with MICs. The examination of the results of these assays, however, revealed that there are differences between the data of different laboratories, depending on the microorganisms and conditions used.