Pharmacokinetics of altrenogest in horses

Additional effects using progestins in mares on levels of thyroid hormones and steroids in neonates

The risk of pregnancy loss in mares leads to the use of exogenous hormones to help pregnancy maintenance. The objective was to evaluate the proportion of thyroid hormones and steroids in neonates, in the following postpartum period, born to mares fed with synthetic progesterone and to verify the existence of a correlation between the level of progesterone between mother and neonate. Twenty-seven mares and their foals were used. The animals were divided into 5 experimental groups: group 1 (control, without hormonal supplementation), group 2 (random samples fed to 120 days of pregnancy with long-term progesterone), group 3 (mares fed with short-term progesterone as of 280.º day of pregnancy), group 4 (mares fed with long-term progesterone as of 280.º day of pregnancy) and group 5 (mares fed with synthetic hormone [altrenogest] as of 280.º day of pregnancy). The animal's blood collection took place immediately after parturition for the hormonal measurement. The hormones measured in neonates were total T3, free T4, TSH, progesterone and cortisone. In mares, only levels of progesterone. The groups of neonates showed no difference on levels of total T3, free T4, TSH and progesterone. There was no difference on levels of progesterone in mares among the groups. Neonates from groups 4 and 5 had higher and lower cortisone levels, respectively. No neonate showed clinical change. There was also no correlation between levels of progesterone in mares and foals. Thus, hormonal supplementation with long-term progesterone as of 280 days of pregnancy leds to an increase in the neonate's cortisone levels, in the meantime, supplementation with altrenogest as of 280 days of pregnancy caused a decrease on cortisone levels in foals, despite clinical signs have not been observed on these animals.

Administration of Altrenogest to Maintain Pregnancy in Asian Elephants (Elephas maximus)

Simple Summary

The Asian Elephant (Elephas maximus) is an IUCN (International Union of the Conservation of Nature) Endangered species that has interacted with humans for centuries. Despite advances in captive elephant breeding knowledge, worldwide populations continue to decline. Progesterone is a key reproductive hormone for the maintenance of pregnancy in mammalian species. The monitoring of serum progesterone levels has become a key method of management for captive breeding of elephants. The synthetic progesterone, altrenogest, has been administered to multiple species of mammals both for management of estrus and maintenance of pregnancy. This paper details three Asian elephant pregnancies maintained by the administration of altrenogest after endogenous progesterone levels decreased below the point needed to maintain pregnancy. Pharmacokinetic parameters of altrenogest administered orally as a single dose to nonpregnant pilot study elephants are presented as preliminary data on the administration of this drug to Asian elephants as a pharmacological means of maintaining pregnancy to term.

Abstract

Progesterone and progesterone derivatives are key hormones in pregnancy maintenance in mammalian species. Cessation of pregnancy, including birth or miscarriage, is certain if levels of these hormones drop below a given species-specific requirement necessary to maintain pregnancy. The synthetic progestin, altrenogest, is FDA-approved in the United States for suppression of estrus or synchronization and is administered extra-label to multiple species to maintain pregnancies in cases of luteal deficiency or otherwise abnormally low progesterone levels. Three pregnant Asian elephants received altrenogest from 41 to 131 days during the final trimester of pregnancy, with parturition occurring from 15 to 31 days after altrenogest administration stopped. A single dose of 0.2 mg/kg altrenogest administered to two nonpregnant Asian elephants provided pilot pharmacokinetic data. Serum samples from two of the three clinical cases and the two pilot study elephants were analyzed using Ultra Performance Liquid chromatography coupled to a triple quadruple mass spectrometer (UPLC-MS). Small sample numbers limited analysis; however, the following were determined: AUC∞ of 635.4 ± 73.8 ng*h/mL, Cmax of 30.2 ± 14.4 ng/mL at a Tmax of 4 ± 2.8 h, terminal T1/2 of 47.5 ± 3.0 h, MRT of 36.0 + 3.4 h and Vd/F of 1243.8 + 275.0 L/kg. These data and the three described cases serve as an indication that altrenogest can be administered to Asian elephants as an exogenous progestin to support pregnancy in elephant pregnancies with low endogenous progestin levels.

Altrenogest treatment reduces the stress response of three-year-old warmblood mares during their initial equestrian training

Horse mares are frequently treated with the progestin altrenogest with the aim to suppress estrous behavior and its negative impact on equestrian performance. Progestogens, however, also have sedative effects in males, and females of different species. The aim of our study was therefore to investigate altrenogest-induced changes in the stress response of female horses during initial equestrian training. Three-yr-old Warmblood mares were randomly assigned to treatment with altrenogest (ALT; 0.044 mg/kg once daily; n = 6) or sunflower oil (CON; n = 5) for 12 wk during training. At predefined steps of the training program (free movement, lunging without and with side reins, lunging with saddle, mounting of a rider, free riding, riding by an unfamiliar rider) salivary cortisol concentration, and heart rate were determined from 60 min before to 120 min after training. The same procedures were performed during repeated gynecologic examinations and 2 novel object tests. Bodyweight and body condition scores (BCS) were assessed at 4-wk intervals. During all training units, salivary cortisol concentration and heart rate increased (P < 0.001), but the increase was smaller in group ALT mares (time x treatment P < 0.001). Gynecologic examinations and novel object tests induced a much smaller increase in cortisol and heart rate (P < 0.001) than equestrian training with no difference between groups ALT and CON. Initially, bodyweight, and BCS decreased during training. The subsequent increase was larger in group ALT vs CON (time x treatment P < 0.05). In conclusion, altrenogest reduced the stress response of 3-yr-old mares to equestrian training. The use of altrenogest during equestrian competitions should therefore be reconsidered.

Comprehensive LC-HRMS metabolomics analyses for the estimation of environmental inputs of altrenogest in pig breeding

Altrenogest (ALT), a synthetic progestogen, is used in pig farming for estrus synchronization in gilts. Residues of ALT and its metabolites may reach the aquatic environment via the spread of liquid manure and may present a risk for fish and other higher aquatic organisms due to its endocrine disrupting potential. A pilot study was conducted in which spot urine samples from ALT-treated and non-medicated gilts were collected. We applied LC-HRMS analysis to perform targeted analysis of ALT and known metabolites as well as non-targeted metabolomics analyses to find previously unknown metabolites. The targeted investigation showed that glucuronide conjugates of ALT and its photo-isomerization product are main urinary metabolites of ALT in gilts. Furthermore, an unknown isomerization product of ALT was observed at trace level, whereas ALT and ALT sulfate were not found. The chemometric analysis of non-targeted data revealed a clear difference between ALT-treated gilts and control animals. Furthermore, a hydroxylated ALT glucuronide was identified as highly significant in the ALT-treated group. Additional biomarker annotation and pathway mapping revealed changes in the metabolism of ALT-treated animals which can be explained by ALT's hormonal action. This study illustrates the exceptional potential of LC-HRMS and metabolomics for the detection of potentially new environmental contaminants with high biological activity. Further advantages of the method described are the sampling during routine breeding conditions, a relatively small number of animals required and no particular stress for the animals.

Unravelling androgens in sport: Altrenogest shows strong activation of the androgen receptor in a mammalian cell bioassay

Altrenogest is a commonly used progestogen for the suppression of oestrus and associated distracting behaviours that interfere with training and performance of female racehorses. The steroid is derived from 19-nor testosterone and is structurally similar to the anabolic androgenic steroid, trenbolone. In this study, the relative androgen potency of altrenogest was determined by a kidney (HEK293) cell androgen bioassay. The HEK293 bioassay shows that in its pure form, altrenogest has a high relative potency compared with testosterone but is not as strong as β-trenbolone. Our results also show that altrenogest is able to activate the androgen receptor at the concentrations relevant to the administration regime of racehorses and retains its activity ex vivo. Thus, we show unequivocally that altrenogest, a progestogen used widely in female racehorses, acts as a strong androgen in a mammalian cell bioassay.

Comparative pharmacokinetic study of two kinds of altrenogest oral solutions for sows

This study was to compare the pharmacokinetic characteristics of domestic altrenogest oral solution (DAOS) or imported altrenogest oral solution (IAOS) in healthy sows. A single administration (1 mg/kg body weight) of DAOS or IAOS was performed in sixteen healthy sows according to a two-period crossover design. Plasma concentrations of altrenogest (AT) were measured by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS) and the concentration-time data of AT was analyzed by WINNONLIN 5.2. It was suggested that the main pharmacokinetic parameters of DAOS and IAOS were as follows: C_max was 227.59 ± 83.35 ng/mL and 152.83 ± 80.34 ng/mL, T_max was 1.16 ± 0.52 h and 1.58 ± 0.85 h, t_1/2 was 3.63 ± 0.72 h and 3.45 ± 0.63 h, MRT was 5.02 ± 0.79 h and 5.21 ± 0.87 h, AUC_0-t was 1050.23 ± 409.80 h·ng/mL and 778.22 ± 397.84 h·ng/mL, and AUC_0-∞ was 1060 h·ng/mL and 786 h·ng/mL, respectively. The relative bioavailability of DAOS was 134.9%. Above results indicated that oral DAOS was better absorbed than IAOS, C_max of DAOS was higher than that of IAOS (p < 0.05). However, there was no significant difference in the main pharmacokinetic parameters between oral DAOS and IAOS (p > 0.05). Our data confirmed that the absorption, fast elimination and bioavailability of DAOS in sows were better than those of IAOS.

Pharmacokinetics of altrenogest in gilts

Altrenogest, a synthetic progestogen, is characterized by its estrus synchronization in mares, ewes, sows, and gilts. To investigate the pharmacokinetic profile and evaluate its accumulation in gilts, 18 oral doses of 20 mg altrenogest/gilt/day were given to eight healthy gilts at an interval of 24 hr. Plasma samples were collected, and altrenogest was determined by ultra-high-performance liquid chromatography with mass spectrometry. WinNonlin 6.4 software was used to calculate the pharmacokinetic parameters through noncompartmental model analysis. After the first administration (D 1), the pharmacokinetic parameters, including T_max , C_max , and the elimination half-life (T_1/2λz ), were similar to those observed after the final administration (D 18). However, the mean residence time at D 1 was significantly lower than D 18. As a whole, the mean steady-state plasma concentration (C_ss ), degree fluctuation (DF), accumulation factor (R_ac ), and area under the plasma concentration-time curve in steady state (AUC_ss ) were 22.69 ± 6.15 ng/ml, 270.64 ± 42.51%, 1.53 ± 0.23, and 544.63 ± 147.49 ng hr/ml, respectively. These results showed that after 18 consecutive days of oral administration of altrenogest, plasma concentrations of altrenogest had a certain degree of fluctuation, without significant accumulations.

Alteration of the mare's immune system by the synthetic progestin, altrenogest

PROBLEM

Progestins are immunomodulatory in a variety of species. In the horse, the most commonly administered synthetic progestin is altrenogest (ALT), but its effect on the immune system of the non-pregnant mare is unknown.

METHODS

Peripheral blood mononuclear cells (PBMCs) from diestrous mares were incubated with varying concentrations of progesterone (P4) or ALT to assess intracellular production of IFNγ and the expression of select cytokines. Additionally, ten mares received either ALT or VEH daily utilizing a switchback design beginning on the day of ovulation and continuing for 7 days. Circulating PBMCs and endometrial biopsies were obtained to assess the production and expression of the same cytokines.

RESULTS

In vitro, both P4 and ALT caused a dose-dependent decrease in intracellular IFNγ in PBMCs. P4 caused a dose-dependent decrease in the expression of IFNγ, IL-10 and IL-4, while ALT caused an increase in the expression of IL-6 and IL-1β in PBMCs. In vivo, ALT suppressed the intracellular levels of IFNγ in PBMCs on d6. While control mares experienced a decrease in IL-1β expression from d0 to d6, ALT-treated mares did not. In the endometrium, ALT increased the expression of IL-1RN and IFNγ in comparison with VEH-treated mares.

CONCLUSION

P4 and ALT appear to alter the immune system of the non-pregnant mare both systemically in addition to locally within the endometrium. Further research is necessary to determine the pathways through which this synthetic progestin functions on the immune system of the horse, and the consequences it may have.

Pharmacokinetics of Intrarectal Altrenogest in Horses

Hospitalized pregnant mares being held nil per os (PO) because of medical or surgical events present a dilemma for pregnancy maintenance therapy, which commonly includes oral altrenogest. Rectal administration of medications is a recognized route for achieving systemic concentrations, but there are no data on the pharmacokinetics of rectal altrenogest administration in horses. The purpose of this study was to determine the pharmacokinetics of altrenogest following PO or per rectum (PR) administration in mares. Using a randomized two-way crossover study design, six horses received altrenogest (0.088 mg/kg; PO or PR q 24 hours for 5 days), with a 7-day washout period, and the concentrations of altrenogest were determined by an ultrahigh performance liquid chromatography with tandem mass spectrometry. Plasma concentrations persisted above presumed therapeutic concentrations for a mean of 36 hours (range 24-72 hours) and 5.5 hours (range 3-8 hours) for PO and PR administration, respectively. The calculated half-life (T ½) of PO administration (7.01 ± 3.13 hours) was correspondingly increased when compared to PR administration (2.82 ± 1.07 hours). Relative bioavailability of altrenogest following PR administration was only 5.47%. Altrenogest is rapidly absorbed following PR administration in the horse and reaches therapeutic concentrations, making this a viable method of treatment in NPO mares. The decreased bioavailability and shorter detection time suggest 0.088 mg/kg PR q 4-8 hours would be necessary to maintain therapeutic concentrations over a 24-hour period.

Concentrations of altrenogest in plasma of mares and foals and in allantoic and amniotic fluid at parturition

Treatment with the progestin altrenogest is widely used in pregnant mares. The fact that foals born from healthy mares treated with altrenogest until term suffered from neonatal problems raises the question of direct effects of altrenogest on vital functions in the neonate. We have therefore investigated altrenogest concentrations in maternal and neonatal blood plasma and in fetal fluids. Pregnant mares were treated with altrenogest orally once daily (0,088 mg/kg bodyweight, n = 7) or left untreated (n = 8) from 280 d of gestation until foaling. Altrenogest concentration was determined in plasma of the mares, their foals and in amniotic and allantoic fluid. The concentration of altrenogest in plasma from treated mares (2.6 +/- 1.0 ng/mL) was significantly lower than in plasma from their foals immediately after birth (5.6 +/- 1.9 ng/mL; p < 0.05), but was significantly higher than in their fetal fluids (amniotic fluid: 0.4 +/- 0.1 ng/mL; p < 0.05; allantoic fluid: 3.0 +/- 1.5 ng/mL). Altrenogest was undetectable in maternal and fetal plasma and fetal fluids of control pregnancies at all times. Altrenogest concentration in plasma of foals from treated mares was strongly correlated to the altrenogest concentration in plasma of their dams (r = 0.938, p < 0.001) and in amniotic (r = 0.886, p < 0.001) and allantoic fluid (r = 0.562, p < 0.05). A significant decrease in altrenogest concentration between the time periods 0-15 min, 30-120 min, and 180-360 min after parturition was seen in the plasma from foals born to altrenogest-treated mares. In conclusion, our data demonstrate that altrenogest reaches the equine fetus at high concentrations.

Comprehensive plasma-screening for known and unknown substances in doping controls

Occasionally, doping analysis has been recognized as a competitive challenge between cheating sportsmen and the analytical capabilities of testing laboratories. Both have made immense progress during the last decades, but obviously the athletes have the questionable benefit of frequently being able to switch to new, unknown and untested compounds to enhance their performance. Thus, as analytical counteraction and for effective drug testing, a complementary approach to classical targeted methods is required in order to implement a comprehensive screening procedure for known and unknown xenobiotics. The present study provides a new analytical strategy to circumvent the targeted character of classical doping controls without losing the required sensitivity and specificity. Using 50 microL of plasma only, the method potentially identifies illicit drugs in low ng/mL concentrations. Plasma provides the biological fluid with the circulating, unmodified xenobiotics; thus the identification of unknown compounds is facilitated. After a simple protein precipitation, liquid chromatographic separation and subsequent detection by means of high resolution/high accuracy orbitrap mass spectrometry, the procedure enables the determination of numerous compounds from different classes prohibited by the World Anti-Doping Agency (WADA). A new hyphenated mass spectrometry technology was employed without precursor ion selection for higher collision energy dissociation (HCD) fragmentation experiments. Thus the mass spectra contained all the desired information to identify unknown substances retrospectively. The method was validated for 32 selected model compounds for qualitative purposes considering the parameters specificity, selectivity, limit of detection (<0.1-10 ng/mL), precision (9-28%), robustness, linearity, ion suppression and recovery (80-112%). In addition to the identification of unknown compounds, the plasma samples were simultaneously screened for known prohibited targets.