Radioimmunoassay of unconjugated plasma ethynylestradiol in women given a single oral dose of ethynylestradiol or mestranol.

A method for the radioimmunoassay of ethynylestradiol in plasma is described. The sensitivity is 18 pg/ml, recovery 86.5%, and precision 10.9% (coefficient of variation). Normal women, five at each dose level, were given 50 or 80 mug ethynylestradiol or 50, 80, or 100 mug mestranol of uniform bioavailability. Peak plasma levels were consistently obtained in the 1-hour plasma sample with the former compound. With mestranol, the peak levels of ethynylestradiol were lower than with the same quantity of ethynylestradiol and the time-curve of plasma levels much more variable. With this procedure, it is now possible to study certain aspects of the pharmacokinetics of these clinically important compounds.     

Blood plasma levels of deoxynivalenol and its de-epoxy metabolite in broilers after a single oral dose of the toxin

To evaluate the transfer of deoxynivalenol (DON) and its de-epoxy metabolite (de-epoxy-DON) in the plasma of chicken, mashed oats naturally contaminated with 9.5 mg DON/kg were fed to four broilers (35 days age) at a dose of 20 g/bird. Blood samples were then collected from two birds at 1 h, 3 h, and 5 h post-feeding, while from the other two birds at 2 h, 4 h, and 6 h post-feeding. Analysis of DON and de-epoxy-DON was carried out by using liquid chromatography-tandem mass spectrometry after clean-up with immunoaffinity columns. At 1 h, 3 h, and 5 h post-feeding, the average values of plasma DON were 0.35 ng/ml, 0.20 ng/ml, and 0.15 ng/ml, respectively. The corresponding average values of de-epoxy-DON at these time points were 0.70 ng/ml, 0.80 ng/ml, and 0.25 ng/ml, respectively. The sum of DON and de-epoxy-DON appearing in the plasma at 1 h post-feeding in these birds was estimated to be 0.044% of the total DON fed. At 2 h, 4 h, and 6 h post-feeding, the average values of plasma DON were 0.85 ng/ml, 0.45 ng/ml, and 0.30 ng/ml. De-epoxy-DON could not be detected in the birds sampled at 2 h, 4 h, and 6 h post-feeding. The total amount of DON appearing in the plasma at 2 h post-feeding in these birds was estimated to be 0.036% of the DON fed. These data show that the absorption rate of DON is very low in broilers and that there is also a rapid transformation, and clearance from plasma. Furthermore, there appeared to be individual variability in the capacity of birds to de-epoxidise DON.     

Permanent sterility in the male rat after a single oral dose of pipecolinomethyl-hydroxyindane

A single oral dose (150 mg/kg) of DL-6-(N-alpha-pipecolinomethyl)-5-hydroxy-indane maleate dissoved in distilled water was administered to Sprague-Dawley male rats living under controlled conditions. After dosage the male rats cohabited with female rats which were replaced weekly. The incidence of pregnancy was determined for 20 weeks. The male rats were then killed and the testes examined histologically. Results showed subnormal fertility at the 3rd and 4th week, sterility at the 5th week. Sterility persisted until Week 20. Histological evidence showed absence of spermatogenic cells in treated rats with no signs of regeneration.     

Sensitive high-performance liquid chromatographic determination of indomethacin in human plasma: Pharmacokinetic studies after single oral dose

A sensitive high-performance liquid chromatographic assay for the specific determination of indomethacin at concentrations down to 20 ng/ml in human plasma is described.

This method has been applied to investigate the disappearance of indomethacin from plasma of ten subjects following the intake of two formulations (Indocid® and generic form). An initial half-life of 1.32 ± 0.44 h⁻¹ was found which is in good agreement with other findings, but the terminal phase was much longer (13.6 ± 6.9 h⁻¹) than previously reported. There is no difference between the two galenic forms (p <0.001).     

Chemical ionisation mass fragmentographic measurement of dothiepin plasma concentrations following a single oral dose in man

A method is described for the measurement of the antidepressant drug dothiepin in human plasma.The procedure involves the addition of deuterodothiepin as an internal standard, extraction and measurement by chemical ionisation mass fragmentography. The minimum measurable concentration of 0.5 ng/ml enabled the pharmacokinetics of dothiepin in man to be studied after a single oral dose of 75 mg of dothiepin hydrochloride.Unlike other tricyclic antidepressants the apparent half-life of elimination (approximately 24 h) showed very little intersubject variation. However, the apparent volume of distribution was much more variable and could account for the wide range of steady state concentrations which have been found in patients taking dothiepin.     

Rapid return of cyclo-oxygenase active platelets in dogs after a single oral dose of aspirin

A single dose of oral aspirin in human subjects inhibits the aggregation response of platelets to arachidonate and other agents for approximately one week after ingestion. In the present study we have evaluated the rate at which cyclo-oxygenase active platelets return to the circulation in humans and dogs and compared the response curves obtained to improvements in cyclo-oxygenase activity produced by the aspirin platelets. After a single dose of aspirin, dog platelet function was compromised for several days. Normal responses to arachidonate and other aggregating agents were restored six days after aspirin, and the pattern of recovery was the same for dogs and human subjects. However, cyclo-oxygenase active platelets returned to the circulation in dogs more rapidly than in humans and chemical competence was restored in both species well before correction of the defective response to aggregating agents. The delay of 1-3 days before return of significant numbers of cyclo-oxygenase active platelets most likely reflects acetylation of bone marrow megakaryocytes by the drug. More rapid return of chemically competent cells in dogs than humans probably relates to the more rapid turnover and shorter life span of canine platelets. The basis for the discrepancy in return of chemical integrity compared to functional activity after aspirin in vivo compared to simultaneous correction of chemistry and function when 10% normal platelets are added to aspirin platelets in vitro remains unresolved.     

Effects of oral L-tyrosine administration on CSF tyrosine and homovanillic acid levels in patients with Parkinson's disease

To determine whether 1-tyrosine administration can enhance dopamine synthesis in humans as it does in rats, we measured levels of tyrosine and the major dopamine metabolite, homovanillic acid, in lumbar spinal fluids of 23 patients with Parkinson's disease before and during ingestion of 100 mg/kg/day of tyrosine. Nine patients took 100 mg/kg/day of probenecid in six divided doses for 24 hours prior to each spinal tap; 14 patients did not receive probenecid. L-tyrosine administration significantly increased CSF tyrosine levels in both groups of patients (p less than .01) and significantly increased homovanillic acid levels in the group of patients pretreated with probenecid (p less than .02). These data indicate that l-tyrosine administration can increase dopamine turnover in patients with disorders in which physicians wish to enhance dopaminergic neurotransmission.     

A novel potent indazole carboxylic acid derivative blocks spermatogenesis and is contraceptive in rats after a single oral dose

Women have historically been the focus for development of new contraceptive methods. The National Institutes of Health, World Health Organization, and Institute of Medicine have stressed the need to develop nonhormonal, nonsteroidal male contraceptive agents. We report results from initial dose-ranging studies of a new indazole carboxylic acid analogue, gamendazole. An infertility rate of 100% was achieved in seven out of seven proven-fertile male rats 3 wk after a single oral dose of 6 mg/kg of gamendazole. Fertility returned by 9 wk in four of seven animals, with typical numbers of normal-appearing conceptuses. A fertility rate of 100% returned in four of six animals that became infertile at a single oral dose of 3 mg/kg of gamendazole. No differences in mating behavior were observed in either of the gamendazole-treated groups versus the control (vehicle-only) group. In the animals that showed reversible infertility, a transient increase in circulating FSH levels coincided with an initial decline in inhibin B levels after administration of gamendazole, but no other significant changes in circulating reproductive hormones were observed. Gamendazole inhibited production of inhibin B by primary Sertoli cells in vitro with a median inhibitory concentration of 6.8 thorn+/- 3.0 (SEM) (3/4)x 10(-10) M, suggesting that Sertoli cells are a primary target. A biotinylated gamendazole analogue revealed cytoplasmic and perinuclear binding of gamendazole in primary Sertoli cells. Gamendazole represents the most potent new oral antispermatogenic indazole carboxylic acid to date. Our results, however, demonstrate that additional dose-finding studies are required to improve reversibility and widen the therapeutic window before more detailed drug development of this potential nonhormonal male contraceptive agent can occur.     

Calcium absorption in corticoid treated subjects effects of a single oral dose of calcitriol

We compared the fractional absorption of calcium (FACa, 6 h, % TD) and the radiocalcium transit (% TD per min) in seven glucocorticoid-treated patients (10-25 mg prednisolone per day) and in seven normal subjects, in the basal state and 12 h after an oral dose of synthetic 1,25-(OH)2D (3 micrograms). In the basal state, the radiocalcium transit was significantly decreased (P less than 0.02) at 15 min in patients treated with prednisolone, but FACa at 6 h was not significantly decreased (51 +/- 5 vs. 60 +/- 5% TD). 12 h after an oral dose of 1,25-(OH)2D which resulted in supraphysiologic plasma levels, FACa increased significantly (P less than 0.02) in both groups but the peak absorption rate of Ca remained lower in the corticoid-treated patients than in controls (P less than 0.02). The results suggest that glucocorticoids decrease the 1,25-(OH)2D-dependent transport of calcium across the proximal small intestine.     

Development of bioreactor system for L-tyrosine synthesis using thermostable tyrosine phenol-lyase

An efficient enzyme system for the synthesis of L-tyrosine was developed using a fed-batch reactor with continuous feeding of phenol, pyruvate, and ammonia. A thermo- and chemostable tyrosine phenol-lyase from Symbiobacterium toebii was employed as the biocatalyst in this work. The enzyme was produced using a constitutive expression system in Escherichia coli BL21, and prepared as a soluble extract by rapid clarification, involving treatment with 40% methanol in the presence of excess ammonium chloride. The stability of the enzyme was maintained for at least 18 h under the synthesis conditions, including 75 mM phenol at pH 8.5 and 40 degrees C. The fed-batch system (working volume, 0.5 1) containing 1.0 kU of the enzyme preparation was continuously fed with two substrate preparations: one containing 2.2 M phenol and 2.4 M sodium pyruvate, and the other containing 0.4 mM pyridoxal-5-phosphate and 4 M ammonium chloride (pH 8.5). The system produced 130 g/l of L-tyrosine within 30 h, mostly as precipitated particles, upon continuous feeding of the substrates for 22 h. The maximum conversion yield of L-tyrosine was 94% on the basis of the supplied phenol.     

Correlation between ACE activity and mean blood pressure in Iranian normotensive subjects after oral administration of a single dose of enalapril

Relationship between serum ACE activity and mean blood pressure (MAP) after administration of a single oral dose of the ACE inhibitor enalapril 10 and 20 mg tablets was investigated in 19 Iranian normotensive male subjects. Enalapril at doses, which maximally inhibit ACE activity, reduced MAP dose dependently. The t(max) of ACE inhibition decreased significantly by increasing the enalapril doses, but t(max) of MAP reduction did not change by increasing the dose. The AUC (area under the curve) of ACE inhibition versus time was significantly larger in 20 mg enalapril group compare to 10mg enalapril group (p<0.001). A significant correlation was found between log of residual ACE activity and MAP (r=0.4927; p<0.001). It is concluded that in Iranian normal subjects, after administration of a single oral dose of enalapril, MAP related to residual ACE activity.     

Limited antioxidant effect after consumption of a single dose of tomato sauce by young males,despite a rise in plasma lycopene

This study investigated the effect of a single dose of tomato sauce on healthy male volunteers in a randomized crossover study. Healthy male subjects (n = 10) were enrolled. Placebo (rice and olive oil) or tomato (tomato sauce, rice and olive oil) meals were provided to the volunteers. Blood and urine samples were taken before consumption of meal (0 h) and 2, 4, 6, 24 and 48 h after meal. Consumption of tomato sauce increased plasma lycopene level by 5–22%, with a maximum level at 24 h (p<0.01) after the meal. Levels of plasma F₂-isoprostanes, hydroxyeicosatetraenoic acid products, allantoin and urinary 8-hydroxy-2′-deoxyguanosine did not change after either meal, but urinary F₂-isoprostanes (p<0.05) significantly decreased at 48 h compared to 0 h after the tomato sauce meal. This study showed that a single dose of tomato sauce meal had only a limited antioxidant effect in vivo.     

Efficacy of a small single dose of oral dexamethasone for outpatient croup: a double blind placebo controlled clinical trial.

OBJECTIVE--To assess the efficacy of a single dose of oral dexamethasone 0.15 mg/kg in children with mild croup not admitted to hospital. DESIGN--Double blind, randomised, placebo controlled clinical trial. SETTING--The emergency department of a tertiary paediatric hospital. SUBJECTS--100 children aged 4-122 months presenting with mild croup. INTERVENTION--A single oral dose of dexamethasone 0.15 mg/kg or placebo. MAIN OUTCOME MEASURE--Return to medical care with ongoing croup. RESULTS--Baseline characteristics of the two treatment groups were similar. Eight children (all from the placebo group) returned to medical care with ongoing croup, one being admitted. There was no reported difference in duration of croup symptoms, duration of viral symptoms, or rate of return to medical care for other reasons. CONCLUSION--Oral dexamethasone in a dose of 0.15 mg/kg is effective in reducing return to medical care with ongoing croup in children with mild croup.