Browsing by Author "Parkin, D. P."

Now showing 1 - 8 of 8
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    Cortical lens opacities in the young patient - an indication for a lipogram?
    (Health & Medical Publishing Group, 2001) Meyer, D.; Maritz, F. J.; Liebenberg, P. H.; Parkin, D. P.; Burgess, L. J.
    Aim. To determine the characteristics and prevalence of lenticular opacification in patients with underlying dyslipidaemia. Methods. Eighty patients of both genders and all ages (18 - 90 years) were enrolled in the trial if they met the inclusion criteria for dyslipidaemia. Patients were included if their fasting serum cholesterol and triglyceride concentrations were > 5.2 mmol/1 and > 2.3 mmol/1, respectively, when measured on three separate occasions over a 1-month period. Patients were excluded if they suffered from any condition known to cause or predispose them to elevated lipid levels or lenticular opacification. Lenticular changes were assessed by means of a slit-lamp through the fully dilated pupil and other physical signs were documented subsequent to thorough physical evaluation. Results. In addition to the classic clinic signs of dyslipidaemia, 31% of patients had cortical lens opacities. Cortical opacities were twice as prevalent as Achilles tendon thickening (16.3%) in our study, the second most prevalent sign of elevated lipid levels. In the subgroup of patients aged under 50 years, 55% had lenticular opacities, predominantly cortical (80%). Conclusions. Cortical lens opacification was the most prevalent sign of dyslipidaemia and it occurred at a relatively young age in our trial population in those patients who were affected. Cortical lenticular opacification should be regarded as an indication for blood lipid profile evaluation.
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    Early bactericidal activity of ethambutol, pyrazinamide and the fixed combination of isoniazid, rifampicin and pyrazinamide (Rifater) in patients with pulmonary tuberculosis
    (Health & Medical Publishing Group, 1996) Botha, F. J. H.; Sirgel, F. A.; Parkin, D. P.; Van de Wal, B. W.; Donald, P. R.; Mitchison, D. A.
    The early bactericidal activity (EBA) of ethambutol, pyrazinamide and the fixed combination of isoniazid, rifampicin and pyrazinamide (Rifater: Mer National) was evaluated in patients with pulmonary tuberculosis who were sputum-positive on microscopy for acid-fast bacilli. Twenty-eight patients (mean age 33 years and weight 51 kg on average; range 40-59 kg) were studied. The fall in viable counts of Mycobacterium tuberculosis in sputum collections during the 2 days following the start of treatment was estimated from counts of colony-forming units (CFUs) of M. tuberculosis per ml of sputum cultured on selective 7H10 agar medium. The EBA for ethambutol determined in 9 patients was 0.245 ± 0.046, log10 CFU/ml sputum/day, that for pyrazinamide was 0.003 ± 0.014 log10 CFU/ml sputum/day and that for Rifater 0.558 ± 0.054 log10 CFU/ml sputum/day. The results obtained are similar to those reported in a previous study of the first 2 days of treatment, but in smaller numbers of patients, and confirm the moderate EBA of ethambutol while pyrazinamide is again shown to have very little EBA. Rifater has a marked EBA which may be due mainly to the action of isoniazid. This methodology may be valuable in the rapid evaluation of the bactericidal activity of new antituberculosis agents and the comparison of different dose sizes of agents of the same class.
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    Endogenous immunoreactive digitalis-like substance in neonatal serum and placental extracts
    (Health & Medical Publishing Group, 1984) Beyers, A. D.; Spruyt, L. L.; Seifart, H. I.; Kriegler, A.; Parkin, D. P.; Van Jaarsveld, P. P.
    Therapeutic levels of digoxin in the serum of untreated neonates delivered to mothers who had not received the drug prenatally were detected by radio-immunoassay. Digoxin levels in neonates should be interpreted with care because of the unknown contribution by the endogenous digitalis-like substance (DLS) to the level of the drug. Three commercially available radio-immunoassay kits were compared with regard to their sensitivity and reproducibility in detecting the endogenous DLS. The kit from Clinical Assays (Cambridge, Mass., USA) was selected for further investigations. In a series of 35 paired samples of maternal and cord blood the average DLS values in terms of digoxin were 0.52 ± 0.07 and 0.81 ± 0.27 ng/ml respectively. This difference is statistically highly significant. In the case of infants with DLS values of 1-1.5 ng/ml in terms of digoxin, approximately 1 week was required to reach non-therapeutic digoxin levels, i.e. below 0.5 ng/ml. Gel chromatography showed that the DLS in neonatal serum was more closely associated with protein than is authentic digoxin. In placental extracts it followed the elution profile of the protein completely, but it shifted to fractions with a lower molecular weight than haemoglobin after trypsinization. The level of DLS in neonatal serum was also increased by more than half its original value by trypsinization. Proteolysis therefore seems to have a releasing effect on DLS. The molecular size of this substance is probably in the same range as that of polypeptides, since it was not dialysable from trypsinized and untreated samples through a membrane with a 22,000 dalton molecular weight cut-off point.
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    Oligomeric substances in ampicillin preparations : a comparison of Penbritin, Famicillin and Petercillin
    (Health & Medical Publishing Group, 1988) Van der Bijl, P.; Seifart, H. I.; Parkin, D. P.; Mattheyse, F. J.
    An investigation into the presence of potentially harmful oligomers in formulations of ampicillin for parenteral administration available in the RSA was undertaken by means of high-pressure liquid chromatography. Significant differences were found to exist between formulations.
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    'n Oorsig van die bepaling van die vroeë bakterisidiese aktiwiteit van verskeie antituberkilosemiddels
    (AOSIS, 2003) Donald, P. R.; Sirgel, F. A.; Venter, A.; Fourie, P. B.; Parkin, D. P.; Seifart, H. I.; Van de Wal, B. W.; Maritz, J. S.
    The early bactericidal activity (EBA) of an antituberculosis agent is the daily decline in log10 colony forming units of M tuberculosis per ml of sputum during the first two days of treatment with the agent. It reflects the capacity of an agent to kill the actively metabolising organisms in tuberculosis lung cavities. It offers a relatively cheap means to evaluate the antituberculosis activity of an agent in a small group of patients within a matter of months. This article summarizes the authors’ experience in seven published EBA studies and identifies sources of variation in the procedure. The patients who participated in these studies had a mean age of 33 years, a mean weight of 50 kg and there was extensive or massive involvement of the lungs in 55% of patients. The highest EBA values (0,50-0,66) were found in groups of patients receiving isoniazid and the lowest values (0,05 and 0,09 respectively), in patients receiving the aminoglycosides amikacin and paromomycin in a dose of 15 mg/kg body weight. The variation in EBA in 248 patients was 0,0312 and the variation ascribable to the process of sputum production and collection was 0,0233. This implies that the different aspects of sputum production and collection involved in obtaining a representative sputum sample are responsible for most of the variation in EBA results. The selection of patients for inclusion in EBA studies and their ability to co-operate in producing a representative sputum specimen are of critical importance in the successful completion of EBA studies.
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    The possible role of endogenous digitalis-like substance in the causation of pre-eclampsia
    (Health and Medical Publishing Group -- HMPG, 1984-06) Beyers, A. D.; Odendaal, H. J.; Spruyt, L. L.; Parkin, D. P.
    Digoxin levels have been reported in neonatal blood when neither the mother nor the baby had received digoxin. An endogenous digoxin-like substance (DLS) that may be causally related to hypertension has been described. Using a commercially available radio-immunoassay kit, we investigated the presence of an immunoreactive DLS in 21 pre-eclamptic mothers, 36 mothers with normal blood pressure (the control group) and their infants. We found mean DLS levels to be higher in cord blood from infants born to the pre-eclamptic mothers than in cord blood from those born to mothers in the control group. Levels were also higher in cord blood than in maternal blood in both the pre-eclamptic and the control groups. DLS seems to be associated with pre-eclampsia. Although further work is needed for verification, a hypothesis on the possible role of DLS in the causation of pre-eclampsia is presented.
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    Practical management of therapeutic diphenylhydantoin concentrations in children
    (Health & Medical Publishing Group, 1999) Smit, A.; Schoeman, J. F.; Seifart, H. I.; Parkin, D. P.
    Objective. Development of easy, practical methods for the management and optimisation of therapeutic diphenylhydantoin (DPH) concentrations in children. Design: Investigation of DPH concentration profiles and pharmacokinetic parameters in children with poorly controlled epilepsy. Subsequent determination of individual-specific DPH maintenance dosage and volume of distribution data suitable for use in routine therapeutic concentration management procedures. Setting. Department of Paediatrics and Child Health and Department of Pharmacology, University of Stellenbosch, Tygerberg Hospital. Subjects. Children of both sexes between the ages of 4 and 12 years with poorly controlled epilepsy receiving DPH as sole medication. Results. In all subjects evaluated epilepsy was unsatisfactorily controlled because of inadequate DPH dosage regimens. Individual-specific maintenance dosage and volume of distribution data could be calculated for all individuals participating in the trial. The calculated data were suitable for use in routine management procedures and in no instance was it necessary to recalculate parameters in a 12-month follow-up period subsequent to evaluation. Conclusions. Therapeutic DPH concentration profiles can be managed satisfactorily in children if individual-specific DPH pharmacokinetic parameters are derived and skilfully applied.
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    Therapeutic monitoring as an aid in rationalising aminoglycoside dosage techniques in the neonate
    (Health & Medical Publishing Group, 1987) Spruyt, L. L.; Kirsten, G. F.; Parkin, D. P.; Muller, G. J.; Kriegler, A.
    General pharmacokinetic parameters applicable to adults are not suitable in neonatal practice owing to wide interpatient variations in respect of fluid balance, renal clearance and metabolic rates. We attempted to determine whether acceptable blood levels of gentamicin or tobramycin are obtained with dosage regimens and dosage techniques which are generally recommended. Forty neonates receiving aminoglycosides were studied. After administration of the drug as a slow, constant intravenous infusion into the 'Y' connection of the infusion set, peak levels were found to be subtherapeutic. Trough levels were also very low. After administration of the same dose of gentamicin or tobramycin as a bolus into the butterfly connection of the infusion set, however, high therapeutic levels were obtained. We therefore recommend that gentamicin and tobramycin be administered as an intravenous bolus injection and that blood levels be monitored constantly in order to individualise therapy.