Pharmacokinetic-pharmacodynamic study of subcutaneous injection of depot nandrolone decanoate using dried blood spots sampling coupled with ultrapressure liquid chromatography tandem mass spectrometry assays

CONTEXT

Testosterone (T) and nandrolone (N) esters require deep im injections by medical personnel but these often deposit injectate into sc fat so that more convenient sc self-administration may be feasible.

OBJECTIVE

To investigate the feasibility and pharmacology of sc injection of N decanoate in healthy men using dried blood spot (DBS) for frequent blood sampling without clinic visits.

SETTING AND DESIGN

Healthy male volunteers received 100 mg N decanoate by a single sc injection. Finger-prick capillary blood was spotted onto filter paper before injection daily at home for 21 d and stored at room temperature. Venous whole blood was also spotted onto filter paper before and weekly for 3 wk after injection. DBS were extracted for assay of N and T by liquid chromatography tandem mass spectrometry in a single batch with serum concentrations estimated with adjustment for capillary blood sample volume and hematocrit to define peak (N) or nadir (T) time and concentration from individual daily measurements.

RESULTS

Daily serum N peaked 2.50 ± 0.25 (SEM) ng/mL at a median (range) of 6 (4-13) days causing a reduction in serum T from 3.50 ± 0.57 ng/mL at baseline to a nadir of 0.38 ± 0.13 (SEM) ng/mL (89 ± 3% suppression) at a median (range) of 8 (5-16) days. Simultaneously sampled capillary, venous whole blood, and serum gave almost identical results for serum T and N. Finger-pricks and sc injections were well tolerated.

CONCLUSIONS

This study demonstrates that A) DBS sampling with liquid chromatography mass spectrometry steroid analysis achieves frequent time sampling in the community without requiring clinic visits, venesection, or frozen serum storage, and B) androgen esters in an oil vehicle can be delivered effectively by sc injection, thus avoiding the need for medically supervised deep-im injections.

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry method for the determination of dienogest in human plasma and its pharmacokinetic applications under fasting

A simple, rapid and sensitive analytical method using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) detection with positive ion electrospray ionization was developed for the determination of dienogest in human K2 EDTA plasma using levonorgestrel d6 as an internal standard (IS). Dienogest and IS were extracted from human plasma using simple liquid-liquid extraction. Chromatographic separation was achieved on a Zorbax XDB-Phenyl column (4.6 × 75 mm, 3.5 µm) under isocratic conditions using acetonitrile-5 mm ammonium acetate (70:30, v/v) at a flow rate of 0.60 mL/min. The protonated precursor to product ion transitions monitored for dienogest and IS were at m/z 312.30 → 135.30 and 319.00 → 251.30, respectively. The method was validated with a linearity range of 1.003-200.896 ng/mL having a total analysis time for each chromatograph of 3.0 min. The method has shown tremendous reproducibility with intra- and inter-day precision (coefficient of variation) <3.97 and 6.10%, respectively, and accuracy within ±4.0% of nominal values. The validated method was applied to a pharmacokinetic study in human plasma samples generated after administration of a single oral dose of 2.0 mg dienogest tablets to healthy female volunteers and was proved to be highly reliable for the analysis of clinical samples.

Ex vivo spontaneous generation of 19-norandrostenedione and nandrolone detected in equine plasma and urine

19-Norandrostenedione (NAED) and nandrolone are anabolic-androgenic steroids (AASs). Nandrolone was regarded solely as a synthetic AAS until the 1980s when trace concentrations of apparently endogenous nandrolone were detected in urine samples obtained from intact male horses (stallions). Since then, its endogenous origin has been reported in boars and bulls; endogenous NAED and nandrolone have been identified in plasma and urine samples collected from stallions. More recently, however, it was suggested that NAED and nandrolone detected in urine samples from stallions are primarily artifacts due to the analytical procedure. The present study was undertaken to determine whether NAED and nandrolone detected in plasma and urine samples collected from stallions are truly endogenous or artifacts from sample processing. To answer this question, fresh plasma and urine samples from ≥8 stallions were analyzed for the two AASs, soon after collection, by liquid chromatography hyphenated to tandem mass spectrometry (LC-MS/MS). NAED and nandrolone were not detected in fresh plasma samples but detected in the same samples post storage. Concentrations of both AASs increased with storage time, and the increases were greater at a higher storage temperature (37°C versus 4°C, and ambient temperature versus 4°C). Although NAED was detected in some fresh stallion urine samples, its concentration (<407 pg/mL) was far lower (<0.4%) than that in the same samples post storage (at ambient temperature for 15 days). Nandrolone was not detected in most of fresh urine samples but detected in the same samples post storage. Based on these results, it is concluded that all NAED and nandrolone detected in stored plasma samples of stallions and most of them in the stored urine samples are not from endogenous origins but spontaneously generated during sample storage, most likely from spontaneous decarboxylation of androstenedione-19-oic acid and testosterone-19-oic acid. To our knowledge, it is the first time that all NAED and nandrolone detected in plasma of stallions and most of them detected in the urine have been shown to be spontaneously generated in vitro during sample storage. This finding would have significant implications with regard to the regulation of the two steroids in horse racing.

In vivo MRI evaluation of anabolic steroid precursor growth effects in a guinea pig model

Anabolic steroids are widely used to increase skeletal muscle (SM) mass and improve physical performance. Some dietary supplements also include potent steroid precursors or active steroid analogs such as nandrolone. Our previous study reported the anabolic steroid effects on SM in a castrated guinea pig model with SM measured using a highly quantitative magnetic resonance imaging (MRI) protocol. The aim of the current study was to apply this animal model and in vivo MRI protocol to evaluate the growth effects of four widely used over-the-counter testosterone and nandrolone precursors: 4-androstene-3 17-dione (androstenedione), 4-androstene-3beta 17beta-diol (4-androsdiol), 19-nor-4-androstene-3beta-17beta-diol (bolandiol) and 19-nor-4-androstene-3 17-dione (19-norandrostenedione). The results showed that providing precursor to castrated male guinea pigs led to plasma steroid levels sufficient to maintain normal SM growth. The anabolic growth effects of these specific precursors on individual and total muscle volumes, sexual organs, and total adipose tissue over a 10-week treatment period, in comparison with those in the respective positive control testosterone and nandrolone groups, were documented quantitatively by MRI.

Gas chromatography-mass spectrometry method for the analysis of 19-nor-4-androstenediol and metabolites in human plasma: application to pharmacokinetic studies after oral administration of a prohormone supplement

19-Nor-4-androstenediol is a prohormone of nandrolone. Both substances are included in the WADA list of prohibited classes of substances. The aim of this study is to determine the plasma levels of 19-nor-4-androstenediol and its metabolites after oral administration of a nutritional supplement containing the drug. Two capsules of Norandrodiol Select 300 were orally administered to six healthy male volunteers. Plasma samples were collected up to 24h. Samples were extracted to obtain free and glucuronoconjugated metabolic fractions. Trimethylsilyl derivatives of both fractions were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). The method was validated to determine linearity, extraction recovery, limit of detection and quantification, intra- and inter-day precision and accuracy. After administration of 19-nor-4-androstenediol, the main metabolites detected were norandrosterone and noretiocholanolone, mainly in the glucuronide fraction. Nandrolone, norandrostenedione and 19-nor-4-androstenediol were also detected at lower concentrations.

Dienogest is a selective progesterone receptor agonist in transactivation analysis with potent oral endometrial activity due to its efficient pharmacokinetic profile

Dienogest was introduced as an oral progestin. Yet its strong oral potency on endometrial activity is not clearly explained. To circumvent this situation, steroid hormone receptor profiling using transactivation assay and endometrial activity test in rabbits were carried out with determination of plasma drug concentration. Agonistic/antagonistic activity on human progesterone receptor (PR), androgen receptor (AR), glucocorticoid receptor (GR), mineralocorticoid receptor (MR), estrogen receptor alpha (ERalpha), or estrogen receptor beta (ERbeta) were determined. Dienogest activate PR (EC50=3.4 or 10.5 nmol/l) with antagonistic activity on AR (EC50=420.6 or 775.0 nmol/l) but not agonistic nor antagonistic action on GR, MR (3000 nmol/l). Dienogest activate neither ERalpha nor ERbeta (3000 nmol/l). Progesterone activated PR with antagonistic activity on AR and on MR. Dydrogesterone showed a similar profile to progesterone. Norethisterone activated PR, AR, and ERalpha. Medroxyprogesterone acetate activated PR, AR, and GR. Danazol activated PR and AR. Collectively, dienogest has a good specificity to PR compared with the other drugs. By oral treatment, dienogest showed the strongest endometrial activity (ED50=0.0042 mg/kg) in McPhail test among other progestins (ED50 values for MPA, DYG, NES were 0.074, 1.9, >0.05 mg/kg, respectively). Dienogest showed higher plasma concentrations than those of the other progestins with higher doses. The estimated plasma concentration of dienogest at ED50 (3.66 nmol/l) was close to its EC50 value to activate PR. Thus, the stronger oral activity of dienogest could be explained simply by its in vitro potency on PR and its oral pharmacokinetic profile.

Nandrolone Potentiates Arrhythmogenic Effects of Cardiac Ischemia in the Rat

Anabolic steroid abuse has been associated with thrombosis and arteriosclerosis, both of which predispose to myocardial ischemia and infarction. However, there are reports of sudden cardiac death in the absence of thrombus and atheroma following anabolic steroid use. Although treatment with the commonly abused steroid, nandrolone, has been shown to decrease recovery of systolic function following ischemia in isolated rat hearts, it is unknown whether anabolic steroids can increase the incidence of fatal arrhythmia associated with cardiac ischemia. Anesthetized male Sprague-Dawley rats were administered vehicle or nandrolone (10-160 microg/kg/min iv) 10 min prior to 15-min occlusion of the left anterior descending coronary artery followed by 10-min reperfusion. Nandrolone, in this dose range, did not significantly change heart rate, blood pressure, or cardiac rhythm in the absence of ischemia. However, the fraction of rats surviving ischemia was significantly (p < 0.05) decreased by nandrolone at both 40 and 160 microg/kg/min, while survival time during ischemia was decreased significantly (p < 0.001) by nandrolone 160 microg/kg/min. An increase (p < 0.05) in the duration of ventricular fibrillation was noted at the highest compared to the lowest dose of nandrolone, corresponding to a significant increase in the fraction of rats experiencing ventricular fibrillation (p < 0.01). Nandrolone had no effect on the frequency or duration of ventricular fibrillation or survival time during reperfusion. Although the mechanisms underlying these effects are currently unclear, they indicate that exposure to anabolic steroids in combination with transient reductions in coronary blood flow may explain some reports of sudden cardiac death in anabolic steroid users.

Fullerene-C60-modified electrode as a sensitive voltammetric sensor for detection of nandrolone—An anabolic steroid used in doping

The electrochemical behaviour of nandrolone is investigated by cyclic, differential pulse and square-wave voltammetry in phosphate buffer system at fullerene-C60-modified electrode. The modified electrode shows an excellent electrocatalytic activity towards the oxidation of nandrolone resulting in a marked lowering in the peak potential and considerable improvement of the peak current as compared to the electrochemical activity at the bare glassy carbon electrode. The oxidation process is shown to be irreversible and diffusion-controlled. A linear range of 50 microM to 0.1 nM is obtained along with a detection limit and sensitivity of 0.42 nM and 0.358 nA nM(-1), respectively, in square-wave voltammetric technique. A diffusion coefficient of 4.13x10(-8) cm2 s(-1) was found for nandrolone using chronoamperometry. The effect of interferents, stability and reproducibility of the proposed method were also studied. The described method was successfully employed for the determination of nandrolone in human serum and urine samples. A cross-validation of observed results by GC-MS indicates that the results are in good agreement with each other.

7 -Methyl-19-Nortestosterone (MENT) vs Testosterone in Combination With Etonogestrel Implants for Spermatogenic Suppression in Healthy Men

Testosterone with a progestogen can suppress spermatogenesis for contraception. The synthetic androgen 7alpha-methyl-19-nortestosterone (MENT) may offer advantages because it is resistant to 5alpha-reduction and is therefore less active at the prostate. This study aimed to investigate MENT implants in combination with etonogestrel on spermatogenesis, gonadotropins, and androgen-dependent tissues in comparison with a testosterone/etonogestrel regimen. Healthy men (n = 29) were recruited and randomized to receive 2 etonogestrel implants with either 600-mg testosterone pellets repeated every 12 weeks or 2 MENT implants for up to 48 weeks. Testosterone concentrations in the testosterone group remained in the normal range. Subjects with 2 MENT implants showed peak MENT levels at 4 weeks with testosterone concentrations of 2 nmol/L. Sperm concentrations fell rapidly to less than 1 x 10(6)/mL at 12 weeks in 8 of 10 subjects in the MENT group and 13 of 16 subjects in the testosterone group with equally suppressed gonadotropins. Thereafter, suppression was not maintained in the MENT group, and 6 men noted loss of libido. Fourteen men completed 48 weeks of testosterone treatment, and all became azoospermic. Hemoglobin concentrations rose, and high density lipoprotein-cholesterol (HDL-C) fell in both groups. The MENT group showed a fall in prostate-specific antigen with no change in bone mass. MENT with a progestogen can achieve rapid suppression of spermatogenesis similar to testosterone, but this promising result was not sustained due to a decline in MENT release from the implants. This dose of testosterone, compared with previous studies using a lower dose with a higher dose of etonogestrel, had nonreproductive side effects without any increase in spermatogenic suppression. These data indicate the importance of the doses of progestogen and testosterone for optimum spermatogenic suppression while minimizing side effects.

Rise of testosterone, nortestosterone, and 17ß-estradiol concentrations in peripheral blood plasma of pigs after sublingual application in vivo

Application of endogenous anabolic steroids to meat producing animals is not allowed in the EU. In other countries application is practised due to a low oral activity based on an efficient first liver passage. This contrasts with pharmacological investigations where steroids were readily absorbed by the buccal and sublingual mucosa using absorption enhancers. An in vivo study was performed to clarify possible absorption after sublingual applications of one milligram portions of either testosterone (T), 17beta-estradiol (E), or nortestosterone (NT) in sesame oil to castrated male pigs (n=5) without specific delivery systems during anaesthesia. Blood samples were drawn using jugular vein catheters for 15 min before and 3h after application. Hormone concentrations were determined by Radioimmunoassay for T and E or Enzymeimmunoassay for NT. For all steroids a slight increase was measurable one minute after application. Maximal values for T, E, and NT were 2.5 ng/ml, 1.5 ng/ml and 4.2 ng/ml, respectively, and were observed after 10 min. The concentrations of the three steroids decreased slowly thereafter but were still significantly elevated 1-3h after application. Oral absorption of steroids without enhancers should be considered in risk analysis.

Quantitative determination of metabolic products of 19-norandrostenediol in human plasma using gas chromatography/mass spectrometry

Prohormones such as 19-norandrostenediol (estr-4-ene-3beta,17beta-diol) have been added to the list of prohibited substances of the World Anti-Doping Agency because they are metabolized to the common nandrolone metabolites norandrosterone and noretiocholanolone. So far, no studies on the metabolism and in vivo conversion of 19-norandrostenediol after oral or sublingual administration have been reported nor have had quantified data on resulting plasma nandrolone levels. In the present study, an open-label crossover trial with eight healthy male volunteers was conducted. After application of capsules or sublingual tablets of 19-norandrostenediol plasma concentrations of 19-norandrostenediol, nandrolone as well as major metabolites (19-norandrosterone and 19-noretiocholanolone) were determined using a validated assay based on gas chromatography/mass spectrometry. The administration of 100-mg capsules of 19-norandrostenediol yielded maximum plasma total concentrations (i.e., conjugated plus unconjugated compounds) of 1.1 ng/ml (+/-0.7) for 19-norandrostenediol, 4.0 ng/ml (+/-2.6) for nandrolone, 154.8 ng/ml (+/-130.8) for 19-norandrosterone, and 37.7 ng/ml (+/-6.9) for 19-noretiocholanolone. The use of 25-mg sublingual tablets resulted in 3.3 ng/ml (+/-1.0) for 19-norandrostenediol, 11.0 ng/ml (+/-6.4) for nandrolone, 106.3 ng/ml (+/-40.1) for 19-norandrosterone, and 28.5 ng/ml (+/-20.8) for 19-noretiocholanolone. Most interestingly, the pharmacologically active unconjugated nandrolone was determined after administration of sublingual tablets (up to 5.7 ng/ml) in contrast to capsule applications. These results demonstrate the importance of prohibiting prohormones such as 19-norandrostenediol, in particular, since plasma concentrations of nandrolone between 0.3 to 1.2 ng/ml have been reported to influence endocrinological parameters.

The effect of sub-chronic nandrolone decanoate treatment on dopaminergic and serotonergic neuronal systems in the brains of rats

Anabolic-androgenic steroids (AASs) are widely abused by adolescents, although persistent AAS use can cause several adverse physical and mental effects, including drug dependence. The first aim of the present study was to study the action of nandrolone decanoate on dopaminergic and serotonergic activities in the brains of rats. In order to evaluate the anabolic or toxic effects of the dosing regimens used, selected peripheral effects were monitored as well. Male Wistar rats were treated for 2 weeks. Injections containing nandrolone (5 and 20 mg/kg, i.m.) or vehicle were given once daily, 5 days a week. The levels of dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites were assayed from dissected brain regions 3 days after the last injection. Blood was collected for chemical assays before, after 1 week treatment and at decapitation. Both doses of nandrolone significantly increased the levels of 3,4-dihydroxyphenylacetic acid (DOPAC), a metabolite of DA in the cerebral cortex, and the higher dose of nandrolone increased the concentrations of 5-HT in the cerebral cortex compared with the vehicle. In addition, after nandrolone treatment, the levels of hemoglobin and erythrocytes increased, and reticulocyte levels decreased. The results suggest that nandrolone at supraphysiological doses, high enough to induce erythropoiesis, induces changes in the dopaminergic and serotonergic neuronal system in the brains of rats. These phenomena may account to some of the observed central stimulatory properties that have been reported following AAS abuse.

Effects of adjuvant androgen on anemia and nutritional parameters in chronic hemodialysis patients using low-dose recombinant human erythropoietin

BACKGROUND

Recombiant human erythropoietin (epoetin) has greatly contributed to improvement of the anemia of chronic renal failure patients on hemodialysis. However, the reduced erythropoietic effect to epoetin and its high cost have induced lots of supplementary treatments. Therefore, we performed a prospective study to evaluate the effects of adjuvant low-dose androgen therapy in patients using a lower-dose of epoetin than the commonly recommended dose on anemia and the nutritional parameters.

METHODS

17 patients of hemoglobin (Hgb) less than 9 g/dL even after being treated with 1,000 U epoetin subcutaneously (s.c.) 3 times per week on a stable status for more than 6 months, who were on hemodialysis at our institution were examined. They were injected with the same dose of epoetin s.c. and nandrolone decanoate 100 mg intramuscularly (i.m.) weekly for another 6 months. Blood test was performed every month before therapy for 6 months and after therapy for 6 months and the mean values were reviewed for comparison.

RESULTS

Hgb (7.75 +/- 0.9 vs 8.99 +/- 1.39 g/dL, p < 0.01) and hematocrit (Hct) (23.68 +/- 2.85 vs 26.66 +/- 3.91%, p < 0.01) were apparently changed before and after adjuvant therapy. Hgb and Hct, weekly dose of epoetin were not statistically different in 9 male patients before and after adjuvant therapy. The weekly dose of epoetin was not statistically different in 8 female patients, but Hgb and Hct (8.02 +/- 0.6 vs 9.72 +/- 1.31 g/dL, 24.54 +/- 1.7 vs 28.74 +/- 3.06%, p < 0.01) were statistically different before and after adjuvant therapy. In comparison between male and female groups, weekly doses of epoetin and nandrolone decanoate were significantly greater in the female group than the male group (epoetin: 50.66 +/- 6.23 vs 61.18 +/- 8.76 U/kg/week, nandrolone decanoate: 1.69 +/- 0.2 vs 2.04 +/- 0.29 mg/kg/week, p < 0.05).

CONCLUSION

Our data show that the adjuvant androgen therapy is effective for the anemia of hemodialysis patients who did not recover from anemia even after being continuously treated with low-dose epoetin.

Non-protein bound dienogest in serum and salivary dienogest in women taking the oral contraceptives Certostat and Valette

Dienogest (17 alpha-cyanomethyl-17-hydroxy-4,9-estradien-3-one) is the progestagen component of the oral contraceptives Certostat and Valette. In contrast to other 19-norsteroid progestagens like levonorgestrel, norethisterone, gestodene and 3-ketodesogestrel, dienogest does not bind to sexual hormone binding globulin (SHBG). The absent binding to SHBG results in a high portion of free, non-protein bound dienogest in serum. In female volunteers taking the oral contraceptives Certostat and Trisiston, the part of non-protein bound dienogest and levonorgestrel, respectively, in serum was determined by the method of centrifugal ultrafiltration. The portion of free dienogest was found to be 9.55 +/- 0.95% (m +/- SD, n = 13) of total serum dienogest. Free levonorgestrel constituted 0.97 +/- 0.14% (n = 12) of total serum levonorgestrel. In an investigation with 47 female volunteers taking Certostat, serum total dienogest was quantified by a specific radioimmunoassay and free dienogest in serum by centrifugal ultrafiltration. In the serum samples with dienogest concentrations in the range of 4.1-57.7 ng/ml, the part of free, non-protein bound dienogest was found to be 8.90 +/- 0.54% of serum total dienogest. There is a high correlation between serum total dienogest and free dienogest (r = 0.989). In another investigation with 20 female volunteers taking the contraceptive Valette, serum total dienogest and salivary dienogest were quantified by radioimmunoassay and free dienogest in serum by centrifugal ultrafiltration. In the serum samples with dienogest concentrations in the range of 7.5-50.6 ng/ml, the part of free, non-protein bound dienogest was 8.78 +/- 0.77% of serum total dienogest. Salivary dienogest constituted 7.99 +/- 0.94% of serum total dienogest showing a high correlation with serum free dienogest (r = 0.953) and serum total dienogest (r = 0.958). The high portion of non-protein bound compound in serum is a characteristic pharmacokinetic feature of dienogest.

Measurement of 19-nortestosterone and its esters in equine plasma by high-performance liquid chromatography with tandem mass spectrometry

A high-performance liquid chromatographic-tandem mass spectrometric (HPLC/MS/MS) method for the determination of 19-nortestosterone and its esters (cyclopentanepropionate, phenylpropionate, and decanoate) in equine plasma is achieved using an atmospheric pressure chemical ionization (APCI) interface in selected reaction monitoring (SRM) mode. The two internal standards used were 16,16, 17-(2)H(3)-19-nortestosterone for 19-nortestosterone and methenolone acetate for its esters. The steroids studied were extracted from plasma samples with a mixture of diethyl ether/n-hexane (9:1, v/v). The quantification limits for 19-nortestosterone, 19-nortestosterone cyclopentanepropionate, 19-nortestosterone phenylpropionate, and 19-nortestosterone decanoate were 0.16, 5.0, 0.1, and 2.0 ng/mL, respectively, when 2 mL of plasma were used. The recoveries of most of the steroids were 71.6-101.0% except for the decanoate, which could be recovered to about 39.8%. The responses were linear, with correlation coefficients varying from 0.9897 to 0.9999 in the concentration range of 0.1 to 50.0 ng/mL for the steroids studied. When applied to equine (mare) plasma samples, the present method allowed detection of 19-nortestosterone up to 23 days after an intra-muscular injection of 400 mg as the decanoate.

Residues of nortestosterone esters at injection sites. Part 1. Oral bioavailability

Injectable esters of 17 beta-19-nortestosterone (beta-NT) have been used illegally for growth promotion in European Union (EU) cattle production. There are no data on oral bioavailability of free beta-NT from beta-NT esters. Adult non-pregnant female Landrace pigs (n = 4) were fitted with jugular vein cannulae and were treated as follows with an appropriate 'flushing out' period between each treatment: an intravenous bolus of beta-NT at 0.1 mg kg-1 body weight (NTi.v.), 300 mg nortestosterone phenylpropionate (NTPP) in oil of arachis administered per os (NTPPoil) and 300 mg NTPP in aqueous suspension administered per os (NTPPaq). Blood samples were taken for up to 24 h and analysed for free beta-NT by enzyme immunoassay. Calculation of the area under the plasma time concentration curve (AUC), allowed absolute bioavailability estimations for both oral treatments. Mean bioavailability of beta-NT following NTPPaq was 0.35% (range 0.25-0.41%) compared to 2.25% (range 0.86-2.85%) for NTPPoil. Mean +/- standard error of mean time of maximum plasma concentration (Tmas) of free beta-NT occurred earlier (2.3 +/- 0.6 h) with NTPPoil compared to NTPPaq (10.3 +/- 1.03 h) and the maximum plasma concentration (Cmax) was also greater for NTPPoil compared to NTPPaq (36.1 +/- 6.49 vs. 3.2 +/- 0.31 micrograms l-1). It is concluded that the presence of arachis oil enhances the absorption of NTPP. Notwithstanding the possible effects that cooking and other food processing may have on such injection site residues, extrapolation of these results to man suggests that consumption of NTPP-containing injection sites may result in peak plasma concentrations of free beta-NT which are significantly greater than those observed following injection of NT esters.

Plasma, urinary and biliary residues in cattle following intramuscular injection of nortestosterone laurate

The synthetic androgen 19-nortestosterone (beta-NT) has been used illegally as a growth promoter in cattle production in the European Union. Elimination of beta-NT and its metabolites in plasma, urine and bile was studied in three cattle with cannulated gallbladders following intramuscular injection at a single site of 500 mg of the laurate ester (NTL) containing 300.5 mg beta-NT. Using enzyme immunoassay quantification, plasma Cmax of free beta-NT was 0.5 +/- 0.15 microgram/L (mean +/- SEM). Concentrations of free beta-NT in plasma were consistently greater than the assay limit of quantification (0.12 microgram/L) for 32.7 +/- 13.42 days. Mean residence time for the beta-NT in plasma was 68.5 +/- 20.75 days. Following sample preparation by immunoaffinity chromatography, high-resolution GC-MS was used to quantify beta-NT and alpha-NT in urine and bile. beta-NT was detected irregularly in urine from two of the three animals post injection. The principal metabolite present in the urine, alpha-NT, was detected for 160.3 +/- 22.67 days post injection. Cmax for alpha-NT in urine was 13.7 +/- 5.14 micrograms/L. Mean urinary AUC0-183 days for alpha-NT was 845.7 +/- 400.90 (microgram h)/L. In bile, alpha-NT was the only metabolite detected for 174.3 +/- 8.67 days post treatment. Cmax for alpha-NT in bile was 40.8 +/- 12.70 micrograms/L and mean biliary AUC0-183 days for alpha-NT was 1982.6 +/- 373.81 (microgram h)/L. Concentrations of alpha-NT in bile samples were greater than those in urine samples taken at the same time. The mean ratio of biliary:urinary AUC0-183 days was 3.0 +/- 0.72. It is concluded that bile is a superior fluid for detection of alpha-NT following injection of NTL, owing to the longer period during which residues may be detected after administration.

Androgen receptors and skeletal muscle composition in trotters treated with nandrolone laureate

To study the effects of nandrolone laureate (19-nortestosterone) on muscle hypertrophy and concentration of androgen receptors (AR), biopsy specimens were taken from the middle gluteal muscle of 6 Finnhorse trotters (geldings and mares) undergoing training before, immediately after, and 13 weeks after a 14-week treatment with nandrolone. Another 6 similarly trained horses served as controls. An additional 10 mares and 10 geldings were used to study annual variation in muscle concentration of AR. AR was immunohistochemically localized in the nuclei. AR concentration remained constant during the first 14 weeks of the study, but increased significantly during the 13-week follow-up period in both groups. This finding can be explained by the annual variation in AR. In the anabolic steroid (AS)-treated horses, but not in the controls (C), the cross-sectional area of the type I fibres increased significantly during the treatment period, and the percentage of type IIA fibres correlated positively with AR concentration at the end of nandrolone treatment. In the AS group, the concentration of DNA decreased during the 13-week follow-up period, and the percentage of H-chains in the isoenzymes of LDH increased. Protein concentration increased in both groups during the follow-up period. Glycogen content and the activity of citrate synthase in muscle during the study remained unchanged. It can thus be concluded that AS produce differing effects on type I and type II fibres, and the AR concentration in equine muscle may contribute to the change observed in the middle gluteal muscle.

Use of filter paper for sample collection and transport in steroid pharmacology

Field studies of androgen pharmacology are complicated by the necessity to collect, process, and store blood samples in a central facility. We have assessed the feasibility of using capillary blood spots collected by fingerprick and dried on filter paper for pharmacokinetics and pharmacodynamic measurements with nandrolone and testosterone RIAs modified for extracts from capillary blood spots. Assays on punched spots of 7.9-mm diameter (14.9 microL of dried blood) permitted accurate quantification of testosterone down to 0.4 nmol/L from a single spot and nandrolone down to 0.9 nmol/L from two spots. Stability of the steroids in dried blood spots to adverse environmental conditions, notably increased temperatures, was investigated both in the laboratory and in field studies of dried spots sent through the postal system. Storage or postal transport under moderate conditions appeared to have no deleterious effects on apparent androgen concentrations. However, under extreme conditions of storage at 50 degrees C for a week or more, or transport to a very hot tropical location, a rise in the final concentration of nandrolone, and, to a lesser extent, testosterone when corrected for tracer recovery, was noticed. These effects were largely due to apparent susceptibility of tritiated tracer, but not unlabeled androgen, to thermal degradation. In a pilot pharmacological study involving intramuscular injection of 100 mg of nandrolone decanoate in 1 mL of arachis oil, nandrolone concentrations in concurrently collected plasma as well as venous and capillary blood spots showed good agreement. Testosterone concentrations in contemporaneously collected plasma and venous blood spots also showed very good agreement. We propose that these methods may allow patients and experimental subjects to self-collect samples at remote or field locations for convenient mailing to a central laboratory for androgen assay. Applications of this methodology are now under way.

Pharmacokinetics and pharmacodynamics of 7alpha-methyl-19-nortestosterone after intramuscular administration in healthy men

7alpha-Methyl-19-nortestosterone (MENT) is a potent synthetic androgen that is resistant to 5alpha-reductases and therefore less prone to over-stimulate the prostate. It is a good candidate for implant administration in long-term androgen replacement therapy for hypogonadal men or as part of a male contraceptive system. To investigate the pharmacokinetics of MENT after i.m. administration, single i.m. injections of 2, 4 or 8 mg of micronized MENT were given in aqueous suspension to 18 healthy men in two clinics. Blood was sampled frequently for 8 h and 1, 2, 3, 4 and 9 days after the injections. Serum MENT concentrations were determined by radioimmunoassay. Peak MENT concentrations were dose-dependent and were reached about 1-2 h after the injections. Doubling the dose of MENT resulted in an increase of 60% in peak serum MENT concentrations. The mean +/- SE clearance rate was 1790 +/- 140 l/day. The antigonadotrophic activity of MENT was investigated by giving six consecutive daily i.m. injections of 1, 2 or 4 mg of MENT to 24 healthy men in two clinics. Blood was sampled before each injection and up to 24 days after the last injection. Serum testosterone and gonadotrophin concentrations (determined by radioimmunoassay and fluoroimmunoassay respectively) decreased in a dose-dependent and statistically significant manner. The highest dose caused a 74% fall in testosterone, a 70% fall in luteinizing hormone, and a 57% fall in follicle stimulating hormone concentrations. MENT injections did not cause any side-effects. The results show that MENT is a potent antigonadotrophic agent in men.

Experimental administration of 19-nortestosterone and dexamethasone in cattle: elimination of the two drugs in different biological matrices

19-Nortestosterone (19-NT) is one of the mostly recurrent anabolic agents on the black market of illicit drugs. Dexamethasone (DEXA) is licensed for therapy in veterinary practice but its misuse, although often suspected, has seldom been demonstrated. The excretion of 19-NT and DEXA is well documented when the compounds are administered independently but poor information is available in literature for instances when both drugs are administered as a mixture. To evaluate a radioimmunoassay (RIA) for anabolic residues in urine, blood and faeces, the effect of the simultaneous administration and the subsequent elimination of the two drugs, two animals were injected (4 times) with 19-NT and another two (4 times) with 19-NT-DEXA. After preparation and a sequential clean-up on C18 and alumina columns, the samples were analysed by means of a specific 19-NT radioimmunoassay kit and an anti-DEXA antibody. Detection limits for both drugs were 0.5 ppb in blood samples and 2.0 ppb in urine and faecal samples. After the final treatment, positive 19-NT results were recorded at 14 and 21 d in urine and faecal samples, respectively. In the same matrices, positive DEXA values were found at 11 and 28 d, respectively. In the same matrices, positive DEXA values were found at 11 and 28 d, respectively. Urinary excretion was the main metabolic path both for 19-NT and DEXA; only 30% of the residues were excreted via the faeces. The simultaneous injection of DEXA and 19-NT increased the urinary excretion of 19-NT; however, the excretion of 19-NT via faecal matter was similar for both groups.

Impact of suprapharmacological androgenic steroid administration on basal and insulin-stimulated glucose and amino acid metabolism

Effects of androgenic steroids at doses used by athletes were studied in a canine model system in which dosage, diet, and activity were controlled. Dogs were treated with 19-nortestosterone (200 mg/wk intramuscularly) or vehicle and were studied at 18 (n = 4 in steroid and vehicle) or 32 (n = 6 in steroid and n = 4 in vehicle) days. A laparotomy was performed under general anesthesia 17 days before experimentation, and catheters were placed in an artery, portal vein, and hepatic vein. Studies consisted of an equilibration (120 minutes) and a control (40 minutes) period and a three-step immunoreactive insulin euglycemic clamp (1, 2, and 15 mU/kg.min). Step 1 was 150 minutes, and steps 2 and 3 were 90 minutes. Data were collected during the last 30 minutes of each step. Glucose and leucine kinetics were assessed with 3H-glucose and 14C-leucine. Plasma glucose in steroid and vehicle groups was 104 +/- 5 (mean +/- SE) versus 108 +/- 3 mg/dL and 100 +/- 5 versus 107 +/- 4 mg/dL at 18 and 32 days. Glucose turnover was similar at 18 days in steroid and vehicle groups (3.9 +/- 0.3 v 3.6 +/- 0.3 mg/kg.min, respectively), but was elevated in the steroid group at 32 days (5.4 +/- 0.5 v 3.2 +/- 0.4 mg/kg.min). Glucose infusion rates were lower in the steroid group with 15 mU/kg.min immunoreactive insulin at 32 days (15.0 +/- 1.1 v 21.2 +/- 1.4 mU/kg.min). Immunoreactive insulin-independent glucose utilization (Rd) was unaffected at 18 days of steroid treatment, but was increased by almost fourfold at 32 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of anabolic steroid 19-nor-testosterone in bovine serum by GC-SIM-MS

Anabolic steroids extracted from bovine serum by means of organic solvents or solid-phase extraction techniques with C18 cartridges are not suitable for quantitative analysis by gas chromatography-mass spectrometry (GC-MS); therefore, they were extracted from serum by Extrelut columns (Merck; Germany), eluted with diethyl ether, and purified by a solid-phase extraction technique using amino (NH2) columns. The resulting clean extract was treated with heptafluorobutyric anhydride (HFBA); this formed a derivative suitable for GC-MS analysis. Using selected ion monitoring (SIM), quantities as small as 40 pg/mL can be detected.

Experience with 19-nortestosterone in the therapy of systemic lupus erythematosus: worsened disease after treatment with 19-nortestosterone in men and lack of improvement in women

Three men and 4 women with systemic lupus erythematosus (SLE) received 100 mg of 19-nortestosterone decanoate in weekly intramuscular injections over a period of 3 to 24 months. During therapy in the men plasma luteotrophic hormone and free testosterone levels decreased while estrogen levels increased. Anti-DNA antibodies also increased for unknown reasons. Serological changes in two men coincided with an overall increase in the clinical activity of SLE and the appearance of new onset Raynaud's phenomenon and pleuropericardial disease. In contrast, women treated with 19-nortestosterone showed clinical stability despite the persistence of high titer antibodies to DNA, and were able to continue therapy for as long as 16 months in one case. These data indicate that men and women with SLE respond differently to synthetic androgen therapy. Additionally, dissociation of clinical signs and symptoms from serological variables seems possible.

Evidence for the presence of endogenous 19-nortestosterone in the cow peripartum and in the neonatal calf

Urine samples were collected from five Brown Swiss cows during the 18 days prior to and 11 days after parturition and were analysed for 19-nortestosterone using an enzyme immunoassay. Nortestosterone concentrations ranged from 70 to 130 nmol/l in all samples taken before parturition. The levels declined within two days, and 11 days post partum no nortestosterone was detectable. In urine from newborn calves, maximal nortestosterone concentrations were determined during the first day of life (10.9-120 nmol/l), declining below 7.3 nmol/l until day 3 in most animals and remaining below the detection limit (less than 3.6 nmol/l) after day 8 in all animals. There was no obvious difference between cows carrying a male or a female calf nor between newborn male or female calves. Using the combined methods high performance liquid chromatography/enzyme immunoassay and high performance liquid chromatography/gas chromatography-mass spectrometry, the immunoreactivity in urine was identified to be 19-nortestosterone-17 alpha. Although there is unequivocal evidence for the endogenous production of nortestosterone in pregnant cows, its function for placenta physiology, pregnancy anabolism and parturition remains unclear. However, new threshold levels for residue control of nortestosterone need to be fixed in accordance with the endocrine status of the animals.

19-nortestosterone detection in canine plasma after intramuscular administration of 19-nortestosterone phenylpropionate

A proven radioimmunoassay method for monitoring 19-nortestosterone (nandrolone) was combined with high pressure chromatographic fractionation on a microparticulate silica gel using 1,2 dichloroethane/ethanol as the mobile phase. Plasma levels of 19-nortestosterone were monitored for seven days after intramuscular administration of nandrolone phenylpropionate (1.5 mg kg-1) to a beagle and a German shepherd dog. After 24 hours the plasma level in both bitches was 20 ng ml-1 and reverted to baseline after the fourth day after injection. Nandrolone was shown to be the only detectable exogenous steroid present in the post injection plasmas and could be distinguished from any potential cross reacting metabolites. The radioimmunoassay method can therefore be applied to the evaluation of nandrolone in the management of canine chronic renal disease in the bitch.

Studies on the biotransformation of the progestagen dienogest in the rabbit

Following administration of 14 alpha, 15 alpha-3H-Dienogest (STS 557, 17 alpha-cyanomethyl-17 beta-hydroxy-4, 9-estradien-3-one) to female rabbits, extracts from urine, bile and plasma were separated by means of HPLC. Urinary and biliary metabolites are characterized by patterns of high complexity. From the mass spectra and UV absorption data of the urinary Dienogest metabolites a variety of biotransformation reactions has been derived like: hydroxylation in different positions of the Dienogest molecule, among these the 11-position; reduction of the 3-oxo group to 3-hydroxy; introduction of 2 and 4 hydrogen atoms; aromatization of ring A; transformation of 17 alpha-CH2CN to CH2OH, and formation of compounds with a 5(10), 9(11)-diene structure. Some of these reactions occur simultaneously resulting in a very complicated metabolite spectrum. Possibly the multiple effects of Dienogest established in animals are partially caused by metabolites.

Pharmacokinetics of the progestin dienogest (STS 557) in rabbits

Disposition and excretion of the progestin Dienogest (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4,9-dien-3-one, STS 557) were investigated in female rabbits. Following single and repeated administration of the tritium-labelled compound the plasma concentration courses of total radioactivity (Dienogest + metabolites) and of the parent drug alone were estimated and also the urinary and fecal excretion of total radioactivity. From these data basic pharmacokinetic parameters were calculated. Additionally, the enterohepatic recirculation of biliary excreted metabolites was studied using bile of donors for oral administration to recipients. Following oral administration the high bioavailability of Dienogest which was already found in other animal species and in man could also be confirmed with rabbits. The parameters of Dienogest disposition do not differ significantly from those of the progestin levonorgestrel. Thus, the different effects of the both progestins in the McPhail-Clauberg assay in the rabbit cannot be attributed to differences in pharmacokinetics.

Combination of 19-nortestosterone-hexyloxyphenylpropionate (Anadur) and depot-medroxyprogesterone-acetate (Clinovir) for male contraception

Because monotherapy with 19-nortestosterone hexyloxyphenylpropionate (Anadur, Pharmacia Arzneimittel, Ratingen, Federal Republic of Germany) suggested improved results for male contraception compared with available testosterone esters, it was tested for induction of complete azoospermia when combined with depot-medroxyprogesterone acetate (DMPA, Clinovir, Upjohn GmbH, Heppenheim, Federal Republic of Germany). Twelve men were treated for 7 weeks with weekly intramuscular (IM) injections of 200 mg Anadur followed by 3-weekly IM injections of Anadur up to week 15. Clinovir (250 mg) IM was administered at the start of treatment and during weeks 6 and 12. Anadur and Clinovir suppressed serum gonadotropins. Although serum testosterone declined steeply, in general, libido and potency were not impaired. Sperm concentrations were reduced significantly after 3 weeks of treatment. Lowest sperm counts were seen during week 8 of follow-up, when only 2 volunteers showed measurable sperm counts of 2.1 and 3.0 X 10(6)/ml, with a declining tendency. After 43 weeks, sperm concentrations were still below pretreatment range in 2 men, but later returned to pretreatment values. Computerized sperm motion analysis revealed that motility parameters in the residual sperm were reduced. In vitro analysis excluded a direct effect of medroxyprogesterone acetate in seminal plasma on sperm motion. The data indicate that the combination of Anadur with Clinovir increases the rate of azoospermia in normal volunteers seen under Anadur monotherapy, although the goal of azoospermia in all participants was not quite achieved.

Rising plasma levels of 19-nortestosterone throughout pregnancy: determination by radioimmunoassay and validation by gas chromatography-mass spectrometry

A highly sensitive and specific radioimmunoassay was developed to measure 19-nortestosterone (NT), which allowed us to demonstrate this steroid in the plasma of pregnant women. Plasma NT was detectable throughout gestation, reaching values of 12 to 60 pg/ml in the 3rd trimester. These results were validated by gas chromatography-mass spectrometry. No NT was detectable in the plasma of 12 normal men and 12 nonpregnant women in the mid follicular phase of their cycle (detection limit 4 pg/ml). Our results are compatible with current concepts concerning the possible involvement of 19-norsteroids in an accessory biosynthetic pathway for estrogen in the placenta.

A specific radioimmunoassay for the detection of 19-nortestosterone residues in urine and plasma of cattle

19-Nortestosterone (Nandrolone) is illegally used as a growth promoter for meat producing animals. This work describes a radio-immunoassay (RIA) to detect, in cattle urine, Nandrolone and its metabolites. The antiserum was specific for 19-nortestosterone and its main metabolites, and to a lesser extent for Trenbolone (17 beta-hydroxyestra-4,9,11-trien-3-one). The sensitivity of this assay was 6 ug/l at 90 % B0/T binding. This assay can be used in forensic control of illegal treatment with 19-nortestosterone in meat production.

[Radioimmunologic determination of the progestagen dienogest in plasma and saliva]

Following oral administration of 2 mg of dienogest (17 alpha-cyanomethyl-17 beta-hydroxy-4,9-estradien-3-one) to female volunteers, the dienogest concentration courses in plasma and saliva were determined by means of a specific radioimmunoassay (RIA). Three different procedures of the plasma sample preparation prior to the RIA were compared. The dienogest RIA was directly applied to saliva. There is a high correlation between the dienogest concentrations in plasma and saliva. The dienogest plasma elimination half life of about 9 hrs is not significantly different from that derived from saliva. The salivary dienogest concentrations indicate a relatively high non-protein bound portion of this steroid drug in plasma. Following repeated oral administration of dienogest (tau = 24 hrs), there is no significant cumulation of plasma dienogest.

[Radioimmunoassay of the progestagen dienogest using various methods of sample preparation of plasma]

For the radioimmunological determination (RIA) of the progestagen dienogest (1, 17 alpha-Cyanomethyl-17 beta-hydroxy-estra-4,9-dien-3-one) in plasma three methods of sample preparation were tested and compared: Extraction of plasma samples with dichlormethane (I), binding of plasma dienogest to an antiserum added; removal of non-bound steroids by means of activated charcoal, extraction of dienogest using dichlormethane (II), using the RIA without extraction of plasma samples after partial precipitation of proteins by means of ammonium sulphate (III). The reliability of the dienogest-RIA is, characterized by a limit of detection of 3.2 pg (I, III) and 5 pg (II) per tube, respectively, by "within-assay"- and "between-assay" variation coefficients of 3 to 5% and 3 to 9%, respectively, in parallel determinations and by a high rate of recovery of dienogest (greater than 90%) added to plasma. The application of the parallelism test method to different plasma volumes confirms the accuracy of method I and II. When method III was applied to plasma samples with low concentrations of dienogest parallelism wasn't found in all cases.

Clinical trial of 19-nortestosterone-hexoxyphenylpropionate (Anadur) for male fertility regulation

To test the effectiveness of 19-nortestosterone (19NT) as an antifertility agent, 12 normal men (age, 24.0 +/- 2.2 years) received 19NT-hexoxyphenylpropionate (19NT-HPP), 200 mg/week intramuscularly for 7 weeks. After this initial phase, two groups were formed that received injections at different intervals. Except for the 19NT serum levels, there was no difference in treatment effects between both groups. 19NT-HPP administration in general suppressed gonadotropins below detection limits, accompanied by testosterone levels well in the castrate range. At the end of the treatment phase, azoospermia or severe oligozoospermia (total sperm count less than 5 X 10(6)) was present in ten volunteers. No loss of libido or potency was reported. Administration of 19NT-HPP did not affect liver enzymes, creatinine, uric acid, serum electrolytes, or serum lipids. The presented data demonstrate that 19NT-HPP as a single entity given every 3 weeks can suppress sperm output in a high proportion of men and simultaneously maintain virility.

Pharmacokinetics of 19-nortestosterone esters in normal men

A reliable method for the isolation of 19-nortestosterone (NT), testosterone (T) and dihydrotestosterone (DHT) by high-performance liquid chromatography (HPLC) and quantitation of the individual steroids by radioimmunoassays is described. The method was used to measure serum concentrations of NT, T and DHT in a pharmacokinetic study and in a clinical trial for male fertility control. Following intramuscular injection of either 50 mg 19-nortestosterone-3-(p-hexoxyphenyl)-propionate (NP) or 50 mg 19-nortestosterone-decanoate (ND) serum NT increased rapidly to maximal concentrations of 4.6 +/- 3.2 and 2.0 +/- 1.3 nmol/l (+/-SD), respectively, in the 6 volunteers. The half-life time was 8 days for ND and 21 days for NP. Based on these findings a clinical trial with NP was performed. NP was given to 5 healthy men in doses of 100 mg/week for the first 3 weeks followed by 200 mg/week for 10 further weeks. Serum NT levels increased gradually and maximal concentrations were reached in the 13th treatment week (20.2 +/- 3.4 nmol/l). Measurable amounts of NT were detectable for 19 weeks after the last injection. The study shows that NT accumulates under this treatment regime and wider spacing of the injection intervals may be possible in future trials.

Radioimmunoassay for serum levels of an anti-androgen TSAA-291 (Oxendolone) in rats

A simple radioimmunoassay method was established to determine serum levels of a steroidal anti-androgen, TSAA-291 (Oxendolone, 16 beta-ethyl-17 beta-hydroxy-4-estren-3-one) utilizing ether-extract of serum. Using an antiserum raised against TSAA-291-3-oxime-BSA conjugate in a rabbit, a standard curve was obtained in the assay range from 30 pg to 12 ng/tube. Intra- and inter-assay coefficients of variation were calculated to be 11 and 21%, respectively. Recovery rate of unlabeled TSAA-291 was 84%. Cross-reaction with endogenous steroids was less than 0.2%. TSAA-291 estimates were compared with those determined after further purification on a Celite column, or with those assayed with a gas-liquid chromatograph. The difference between these estimates was less than 16 and 25%, respectively, suggesting little contribution of the metabolites of TSAA-291 to the estimates by the radioimmunoassay. After successive treatments of male rats with TSAA-291 in an aqueous suspension in daily doses of 5, 15 and 50 mg/kg body weight for two weeks, serum TSAA-291 levels were determined by the radio immunoassay and calculated to be 22.7, 76.9 and 194.9 ng/ml, respectively.

Plasma concentrations and urinary excretion of nandrolone and/or its metabolites after intramuscular injection of nandrolone phenylpropionate to horses

A radioimmunological method was used as a screening procedure to determine the period of detection or "clearance time", for the horse, of therapeutic doses of the synthetic anabolic steroid nandrolone phenylpropionate. Seven horses, either at rest or being exercised, were given a course of weekly intramuscular injections of the steroid. On the separate occasion, some of the horses were given a single intramuscular injection of the same compound. The weekly injections maintained a high plasma concentration of nandrolone and/or metabolites. The mean (+/- sd) period of detection in plasma of these compounds was 23 (+/- 2) days (range 21 to 25) in resting horses and 20 (+/- 6) days (range 14 to 27) in exercised animals. The mean period of detection in urine was 25 (+/- 7) days (range 16 to 32) and 25 (+/- 12) days (range 9 to 38) for resting and exercised horses, respectively. After a single intramuscular injection to resting horses, the mean periods of detection were 12(+/- 2) days (range 9 to 15) and 13 (+/- 2) days (range 11 to 16) in plasma and urine, respectively. In all experiments there was considerable individual variation in the time taken for the plasma and urine concentrations to return to pre-dose values. This variation was particularly marked in the urine of exercised horses given a course of injections. With horses in training, this period may be over 5 weeks, a period approaching the minimum of 42 days advocated by the Royal College of Veterinary Surgeons that the therapeutic use of anabolic steroids should be discontinued before racing.

Studies related to the metabolism of anabolic steroids in the horse: the identification of some 16-oxygenated metabolites of 19-nortestosterone

1. The metabolism of 19-nor[4-14C]testosterone in a thoroughbred horse has been studied and neutral urinary metabolites obtained after enzyme hydrolysis have been investigated by g.l.c.-mass spectrometry. 2. 3-Hydroxyestran-17-one, 17 alpha- and 17 beta-nortestosterone, estrane-3,17-diol (two isomers), 3,16-dihydroxyestran-17-one (two isomers), 3,17-dihydroxyestran-16-one (two isomers) and estrane-3,16,17-triol were identified in the neutral urinary extracts.

Serum concentrations of mibolerone in Beagle bitches as influenced by time, dosage form, and geographic location

A radioimmunoassay was developed for the assay of mibolerone in the serum of adult bitches with a lower limit of detection of 0.5 ng of mibolerone/ml of serum. Serum concentrations in Beagle bitches given mibolerone were found to be dependent on concentration in and type of formulation. The type of formulation also influenced the time to reach peak serum concentrations of mibolerone. Serum concentrations were also different for the same animals treated at 2 geographic locations.