Biomedical subjects
P Turner
Publications and source records attributed to P Turner.
Dexfenfluramine and neurotoxicity.
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Ocular hypotensive effects of medifoxamine.
Medifoxamine is a novel monoamine re-uptake inhibiting antidepressive drug which preferentially inhibits dopamine reuptake. In human volunteer studies it has been found to reduce significantly intraocular pressure after single oral doses of 300-1000 mg, and to produce a small but statistically significant miosis. Its maximal ocular hypotensive action was less than that of oral timolol 20 mg.
Debrisoquine hydroxylation in Parkinson's disease.
Debrisoquine (DBQ) metabolism was studied in 80 Parkinson's disease (PD) patients, 26 of whom had young onset Parkinson's disease (YOPD), and in 143 controls. There was no significant difference between the proportion of poor metabolisers of DBQ among YOPD patients compared either to other parkinsonians, or to controls. Nor was there a significant correlation between the age of disease onset and DBQ metabolic ratio (MR). The results do not support the suggestion that impairment of DBQ metabolism (and hence cytochrome P450) is a primary defect in YOPD. However, in comparison with controls, MR values were modestly but significantly higher in PD patients, even in those not treated with drugs known to affect DBQ metabolism.
Effects of selective histamine receptor antagonists on skin responses to intradermal bradykinin in healthy volunteers.
The effects of chlorpheniramine and cimetidine on the cutaneous responses to intradermal injections of bradykinin were investigated in a randomized, double-blind, placebo-controlled, cross-over study. Chlorpheniramine significantly attenuated the increase in cutaneous blood flow and erythema induced by bradykinin but not the weal response. Cimetidine was without influence on these parameters and the effects of the combined therapy of chlorpheniramine and cimetidine were not significantly different from those due to chlorpheniramine alone. These results suggest that the cutaneous vasodilator effect of bradykinin is in part due to histamine release acting on histamine H1-receptors.
Absence of potentiation of the skin response to intradermal bradykinin by a long-acting angiotensin converting enzyme inhibitor, trandolapril, at conventional antihypertensive dosage in human volunteers: a double-blind, randomized, cross-over, placebo-controlled trial.
A double-blind, randomized, cross-over, placebo-controlled study was carried out to determine the extent and duration of potentiation of the action of bradykinin introduced intradermally by a long-acting novel angiotensin converting enzyme (ACE) inhibitor, trandolapril. The investigations were performed in a temperature and humidity-controlled laboratory. Intradermal injections of 1 microgram, 2.5 micrograms and 5 micrograms of bradykinin and normal saline (as control) were made into the forearm skin of eight healthy normotensive male volunteers aged 21-33 years (mean 28 years) at baseline, 2, 4, 8, 24, 48, 72 and 96 hours after either 2 mg trandolapril or placebo given orally. Skin blood flow outside the induced weal was monitored by laser Doppler flowmetry (mean of recordings at four sites adjacent to the weal within the flare area). Flare area and weal volume were also measured. Trandolapril reduced the mean arterial pressure. However, there was no evidence that this activity was associated with a potentiation of the cutaneous action of bradykinin. In conclusion, it would appear that potentiation of the action of bradykinin may not be an important contributing factor to the fall in total peripheral vascular resistance associated with ACE inhibition in humans in the control of hypertension.
Does bismuth chelate influence lornoxicam absorption?
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Indomethacin and protein binding of methotrexate.
Indomethacin, a non-steroidal anti-inflammatory drug is known to increase the efficacy and toxicity of methotrexate, the widely used anti-cancer drug in man. The mechanism for this interaction has not been clearly established. However, since these drugs bind with albumin, a possible displacement of methotrexate by indomethacin from albumin might explain this interaction. To investigate the possible interaction an in-vitro protein-binding displacement study was carried out in 17 normal volunteers and in two groups of eight cancer patients. One group of patients had active disease and the other was in complete clinical remission. Serum samples were obtained and protein levels estimated. The protein binding of methotrexate was measured alone and with indomethacin using equilibrium dialysis. Statistical analysis of results suggested that the binding of methotrexate is not influenced by indomethacin, confirming that methotrexate is not displaced by indomethacin.
Benefit:risk consideration in long-term therapy with dexfenfluramine.
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Protein binding of indomethacin, methotrexate and morphine in patients with cancer.
The in vitro protein binding of indomethacin, morphine and methotrexate has been studied in two groups of ten patients each suffering from different types of cancers and compared with twenty normal adult subjects. One group of patients had active disease and the other group was in complete clinical remission. Serum samples were obtained from each subject and the concentrations of albumin and alpha-1 acid glycoprotein (AGP) were measured. Protein binding of drugs was determined using equilibrium dialysis. Alpha-1 acid glycoprotein levels were increased in patients and this effect was more pronounced in active disease (1802 +/- 1025 mg/l) than in remission (931 +/- 273 mg/l). Albumin levels were reduced in active disease (47.67 +/- 15.91 milligrams), but not in remission (61.86 +/- 6.62 milligrams), as compared to control values (58.98 +/- 9.9 milligrams). The protein binding of methotrexate and indomethacin were both reduced in active disease (34.17 +/- 7.12% and 96.26 +/- 0.93% respectively) in comparison with normal subjects (39.33 +/- 4.68% and 96.89 +/- 0.47% respectively), but that of morphine was not changed. In patients there was a strong negative correlation between albumin and alpha-1 acid glycoprotein levels (r = -0.75, p < 0.01) but the correlation in controls was not significant. This study found only weak association between the binding of the drugs studied and the protein levels. It is concluded that reduction in methotrexate dose levels may reduce toxicity in patients with active cancer.
Hepatic beta-adrenoceptor adaptation during propranolol administration is impaired in aging rats.
Aging has been associated with changes in beta-adrenoceptor responses and adaptation to prolonged removal of catecholamine stimulation. We have examined the effect of chronic propranolol administration on rat hepatic membrane beta-adrenoceptor density, agonist affinity and response in young (6-7 months) and old (26-7 months) male Wistar rats. Propranolol administration via miniosmotic pumps for 7 days resulted in similar and sustained plasma propranolol levels (approximately 100 ng/ml) in old and young rats. Pretreatment beta-adrenoceptor responses to isoprenaline were significantly higher in old rats. Propranolol administration was associated with significant increases in beta-adrenoceptor response and density (Bmax) in young rats only. Cyclic adenosine 3',5'-monophosphate (cyclic AMP) responses to prostaglandin E1 (PGE1), guanosine triphosphate (GTP), 5'-guanyl-imidodiphosphate (Gpp(NH)p), forskolin and Mn2+ were not significantly different between young and old rats and were not affected by propranolol administration. Neither aging or propranolol administration was associated with a change in beta-adrenoceptor agonist affinity. These findings demonstrate elevated hepatic beta-adrenoceptor response and impaired hepatic beta-adrenoceptor adaptation to beta-adrenoceptor blockade in aging rats.
The severity of asthma in relation to beta agonist prescribing.
OBJECTS: to investigate the relationship between indices of acute and chronic asthma severity and beta agonist prescribing. METHOD: the severity of asthma was assessed in 120 patients with asthma attending an emergency room. Seventy-seven patients were on salbutamol MDI, 38 on fenoterol MDI and five on different beta agonists. RESULTS: patients prescribed fenoterol MDI had more symptoms of chronic severity than those on salbutamol MDI and were more likely to have had a previous hospital admission. There was no difference in objective measurements of severity on presentation to the emergency room between the groups. CONCLUSIONS: either regular fenoterol MDI use leads to more chronic severe asthma or patients with chronic severe asthma are more likely to have been prescribed fenoterol. Fenoterol use is not associated with delay in presentation with acute asthma.
Iridium implant treatment without external radiotherapy for operable breast cancer: a pilot study.
A pilot study has been conducted to examine a new approach to the treatment of operable breast carcinoma. 27 patients with tumours measuring up to 4 cm in diameter have been treated by tumourectomy, axillary clearance and high dose iridium-192 implant (55 Gy) without any external beam radiotherapy. This enabled the entire local primary treatment of the breast carcinoma to be given in five days. The technique was compatible with adjuvant chemotherapy for those with involved axillary nodes. Local complications have been few and locoregional control has to date been satisfactory. With a relatively short median follow-up of 27 months, cosmesis was objectively rated as good or excellent in over 80% of cases and subjectively rated good/excellent in 96%. High dose brachytherapy now requires testing in a prospective clinical trial to determine whether it is as effective as standard breast conservation techniques for management of early breast cancer.
Fourier transform-Raman spectroscopy for the qualitative and quantitative characterization of sulfasalazine-containing polymeric microspheres.
FT-Raman spectroscopy (FTRS) has been used to characterize microspheres produced from the pharmaceutical polymer Eudragit RS containing a range of concentrations of the drug sulfasalazine. While pure sulfasalazine produced an intense and complex Raman spectrum, the spectrum of drug-free Eudragit RS microspheres was considerably weaker in intensity and contained only a few prominent Raman scattering peaks. In spectra of the drug-polymer microspheres, peaks arising from the individual components could be identified. This enabled a quantitative analysis to be undertaken by calculating the ratio between the area of a sulfasalazine peak and the area of a Eudragit RS peak for each microsphere spectrum. A correlation was shown between the peak area ratio and the microsphere sulfasalazine content. FTRS was then applied to a series of microsphere samples which had been dissoluted into pH 7 buffer for 1, 3, 6, 9, 12, or 24 hr. For each spectrum, the drug-polymer peak area ratio was determined and this in turn enabled calculation of the residual drug content of the microsphere sample. FTRS-calculated data showed good agreement with microsphere drug content values determined spectrophotometrically.
Concentration of metronidazole in cervical mucus and serum after single and repeated oral doses.
The disposition of metronidazole in cervical mucus and serum after single and repeated oral doses (400 mg) was investigated in six healthy female subjects. Metronidazole reached higher concentrations in serum than cervical mucus after both single and repeated oral doses. Metronidazole concentrations in both cervical mucus and serum were high enough to be trichomonicidal and bactericidal. After oral administration, metronidazole concentrations in cervical mucus are due to diffusion rather than ion trapping.
Plasma metronidazole concentrations after single and repeated vaginal pessary administration.
Metronidazole concentrations in plasma were measured by h.p.l.c. in 12 healthy female volunteers after single and repeated vaginal administration of 500 mg metronidazole pessaries. The area under the plasma concentration-time curve (AUC(0,12 h) was 8.4 +/- 3.9 micrograms ml-1 h (mean +/- s.d.) on day 1 and 20.6 +/- 7.1 micrograms ml-1 h (mean +/- s.d.) on day 5. The peak plasma drug concentration on day 1 was 1.2 +/- 0.6 micrograms ml-1 (mean +/- s.d.) and on day 5 it was 2.0 +/- 0.7 micrograms ml-1 (mean +/- s.d.). The plasma concentration of metronidazole at steady state was above the minimum inhibitory concentration (MIC) for anaerobic Streptococci and Clostridium tetani. These results demonstrate much lower systemic exposure than after oral administration.
Concentration of ibuprofen in cervical mucus.
Concentrations of an acidic drug, ibuprofen, in cervical mucus and serum have been measured by HPLC after oral administration in six healthy volunteers. After an 800 mg single dose of ibuprofen, the concentration reached in cervical mucus was less than 4% of that in serum. It is postulated that because ibuprofen is an acidic drug which is not subject to 'ion-trapping' in the acidic environment of cervical mucus, it is not concentrated in this secretion.
Interaction of ketoprofen and frusemide in man.
The effects of ketoprofen on frusemide-induced diuresis, natriuresis and renin release were studied in 12 healthy male volunteers. Each received frusemide 40 mg once daily with either ketoprofen 100 mg twice daily or placebo for two periods of 5 days separated by a treatment-free period according to a randomized, double-blind, cross-over study design. Ketoprofen significantly reduced frusemide-induced diuresis on Day 1 but not on Day 5 of treatment. The natriuresis induced by frusemide on Day 1 or Day 5 of treatment did not differ significantly whether ketoprofen or placebo was administered, although the mean urinary sodium excretion values were consistently lower following ketoprofen. Ketoprofen did not affect the kaliuretic response to frusemide on Day 1 or Day 5 of treatment. The increase in plasma renin activity after frusemide was inhibited by ketoprofen on both Day 1 and Day 5. These results suggest that ketoprofen reduces the diuresis and renin release induced by frusemide, but that the reduction in diuretic response may become less important after their repeated coadministration.