Therapeutic efficacy of aglepristone and mifepristone for pyometra in dogs

Introduction

Canine pyometra, a prevalent reproductive disorder in intact female dogs, occurs primarily during diestrus, characterized by pus accumulation in the uterine lumen and systemic illness (Dow, 1959; Hagman, 2022) [4,11] . Driven by progesterone dominance and bacterial infections, predominantly Escherichia coli, pyometra affects approximately 20% of female dogs before age 10 years (Jitpean, 2012) [18] . Untreated, it risks severe complications like sepsis and organ failure (Hagman, 2022) [11] . Nulliparous and middle-aged dogs are particularly susceptible (Renukaradhya, 2011) [33] . Ovariohysterectomy (OHE) is the standard treatment, effectively eliminating infection but causing sterility (Fieni et al., 2014) [6] . Medical alternatives, such as antiprogestins (aglepristone, mifepristone), block progesterone receptors, promote cervical relaxation, and facilitate uterine evacuation, preserving fertility (Verstegen et al., 2008; Fieni, 2006) [43,5] . This study assesses pyometra incidence and compares the efficacy of injectable aglepristone, oral mifepristone, and their combinations with misoprostol, focusing on clinical, haematological, biochemical, and ultrasonographic outcomes.

Materials and Methods

The study was conducted at the Department of Veterinary Gynecology and Obstetrics, Veterinary College, Hebbal, Bengaluru, from September 2023 to August 2024. Twenty-four female dogs diagnosed with pyometra via clinical signs (e.g., vaginal discharge, anorexia, polyuria) and ultrasonography were randomly assigned to four treatment groups (n = 6 per group): Group I: Aglepristone (10 mg/kg s.c. on days 0, 1, and 7). Group II: Aglepristone (10 mg/kg s.c. on days 0, 1, and 7) plus misoprostol (5 µg/kg orally b.i.d. on days 2 to 6). Group III: Mifepristone (5 mg/kg orally b.i.d. on days 0, 1, and 7). Group IV: Mifepristone (5 mg/kg orally b.i.d. on days 0, 1, and 7) plus misoprostol (5 µg/kg orally b.i.d. on days 2 to 6).

Results

The present research was carried on to compare the therapeutic efficacy of injectable antiprogestin, oral antiprogestin alone and in combination with misoprostol for treatment of pyometra in dogs.

Discussion

No significant differences were observed in mean rectal temperature or heart rate across groups. This observation was same as results obtained by researchers like Unnikrishnan (2018) [41] and (Nayana 2021) [30] who reported marginal hyperthermia on the day of presentation. Sen et al. (2001) [35] found that the temperature was subnormal in patients having generalised toxaemia due to pyometra and normal or slightly higher in patients with open-cervix pyometra whereas, it was elevated in closedcervix pyometra instances. The mean respiratory rate recorded in the current investigation in different treatment protocols before, and after completion of treatment were within normal physiological range (18 to 34/min). However, statistically there was a significant difference in group Ⅳ between day 0 and day 14 Animals in three groups had a normal mean respiratory rate in the study whereas, animals in group Ⅳ had a lesser mean respiratory rate on the day of presentation which improved significantly on day 14 after the completion of treatment. Tiwari et al. (2004) [39] also reported shallow respiration in dogs affected with pyometra. Improvement in respiratory rate might be attributed to reduction in septicaemia and toxaemia after completion of treatment. On the contrary, Renukaradhya (2011) [33] and Unnikrishnan (2018) [41] found no difference in mean respiratory rates as in other three groups of our study. Pretreatment leucocytosis in pyometra affected female dogs in all the four groups in our study. Canine pyometra was characterized by an inflammatory leucogram with a regenerative left shift and a marked increase in the total white blood cell count (Murugavel et [29,26,14,34] . This could be the result of a harsh bone marrow reaction brought on by elevated immune system stress and widespread uterine suppurative inflammation in an effort to fight the infection (Sevelius et al., 1990; Kustritz, 2005) [36,20] . Similar observations of high degree of peripheral leucocytosis along with degenerative left shift with toxic neutrophils were reported (Shukla, 2012) [37] . But after the treatment protocol is initiated, there was a profound reduction in TLC among all the groups after the treatment protocol was introduced, the figures in group Ⅱ and group Ⅳ nearing the normal range on day 14. These observations showed that the severity of the infection decreased as reported by Khan (2006) [23] and Prasad et al. (2017) [31] The mean haemoglobin concentration in the treatment groups before the initiation of treatment were with in normal range .There was evidence of low erythrocyte count in the animals of all groups. This observation is in accordance with the observations made by Hagman et al. (2009) [10] and Jitpean et al. (2014) [19] . According to Verstegen et al. (2008) [43] , the toxic suppression of bone marrow may be the cause of normocytic normochromic anaemia, which is characterized by a packed cell volume of 30 to 35 percent in pyometra. Canine pyometra was also associated with nonregenerative, normocytic and normochromic anaemia. This anaemia subsequently progressed to microcytic, hypochromic anaemia, the severity of which was greater in closed-cervix pyometra cases (Greene, 2006) [9] . Pyometra is a disease of chronic nature in which anaemia is caused by a variety of disorders including chronic inflammation, in which lactoferrin and other acute phase reactants mediate an iron sequestration within the myeloid cells in the bone marrow, withdrawing iron from the normal erythropoiesis. However, it is observed that the haemoglobin and erythrocyte count returned to normal physiological range after the completion of treatment in all groups. Thrombocytopenia occurs in pyometra cases as a result of increased consumption, decreased thrombocyte production in the bone marrow, toxic effects on the bone marrow (Fransson, 2003; Hagman, 2004) [7,12] or increased platelet aggregating factor production mediated by endotoxin (Tsuchiya et al., 1999) [40] . In current study too, initially on the day of presentation there was a lower thrombocyte concentration (within normal physiological range of 200 to 650 (×10 3 /mm 3 )). However, after the initiation of treatment and completion of treatment regime the mean thrombocyte concentration returned to normal range as the endotoxin production decreased. Neutrophilia was noticed among female dogs of all the treatment groups on day 0, suggestive of inflammation. Neutrophilia in pyometra affected female dogs on the day of presentation was reported by Chinnu (2016, 82.67±1.94%) [2] , Unnikrishnan (2018, 83.38±0.46%) [41] and Samantha et al. (2018, 84.6±5.33%) [34] . The marked neutrophilic leucocytosis with shift to left was ascribed to an aggressive bone marrow response to combat the severe bacterial infection in pyometra (Mojzisova et al., 2000) [28] . Neutrophilia reduced over the course of the treatment in the present study, reduction in neutrophil count after the initiation of treatment indicated a reduction in severity of infection, inflammation and bacterial load. There were no significant changes in mean lymphocyte and mean monocyte count in current study as all the values within all the groups among all the days were within normal physiological range. Many authors reported an increase in serum creatinine concentration in pyometra affected dogs (Kuplulu et al., 2009; Hembram et al., 2011; Jena et al., 2014) [24,15,17] , even in the present study initially there was a higher mean serum creatinine concentration. But once the treatment protocol was initiated the mean serum concentration across the groups had decreased and it was in normal physiological range. The normal physiological range of SGPT/ ALT in healthy dogs was 12 to 118 IU/ dL. Even in the current study when the dogs were presented for examination and after the treatment protocol were completed the mean serum SGPT levels were within normal physiological range. However, there was a significant increase in SGPT level in group Ⅱ from 27.67±0.698 IU/dL to 50.92±6.908 IU/dL from day 0 to day 14. This shows the effectiveness of treatment in improving the liver function as in pyometra alanine aminotransferase (ALT) levels were lowered due to hepatic membrane injury or suppression of liver enzyme synthesis, after the treatment in the study the function of liver improved due to improvement in liver enzyme production. The mean serum total protein levels of group I, Ⅱ, Ⅲ and Ⅳ were found to be slightly elevated compared to normal physiological value (5.4 to 7.5g/dL). Similar elevated values were reported by Kaymaz et al. (1999, 7.16±0.92 g/dL) [22] and Maharathi et al. (2020, 8.33±0.30 g/dL) [27] . According to Singh et al. (2006) [38] , female dogs with pyometra may have hyperproteinaemia as a result of an acute phase reaction, which is often linked to inflammation. Mean serum albumin concentration was well within normal physiological range of 2.3 to 3.5 g/dL. All the observations in the study were under normal physiological range. However, in group Ⅳ there was a marginal increase on day 14 in mean serum albumin level. In contrary to this, hypoalbuminemia was recorded by Hagman (2012) [13] which was ascribed to albumin loss through the kidneys and increased gamma globulin synthesis (Borresen and Skrede, 1980) [1] . Reidun et al. (2007) [32] hypothesized that renal albumin loss was the cause of hyper-globulinemia and concurrent hypo-albuminemia. Pre-treatment mean serum globulin (g/dL) of female dogs in group Ⅰ, Ⅱ, Ⅲ and Ⅳ were 5.350±0.4951, 5.050±0.1232, 4.850±0.2156 and 4.650±0.3253, respectively. However, after the initiation of various treatment protocols, mean serum globulin levels decreased. As observed by Johnston et al. (2001) [20] dogs with pyometra were shown to have hypoalbuminemia and hyper-gammaglobulinemia. However, it is observed in the current study that after the initiation of treatment the mean globulin levels decreased. There was a significant decrease in group Ⅱ from day 0 to day 14, showing the effectiveness of treatment protocol in reducing the inflammation of uterus and decreasing gamma globulin Mean uterine lumen diameter (mm) in the present study before treatment in group Ⅰ, Ⅱ, Ⅲ and Ⅳ were 22.54±3.013, 23.21±3.556, 18.92±2.374 and 21.52±2.167, respectively. Increased uterine diameter and wall thickness were associated with anechoic regions in the uterine lumen (Veiga et al., 2017) [42] . Normal dogs had a uterine horn diameter of 6.0±0.4 mm, while dogs with pyometra had a diameter of 28.8±2.2 mm. However, there was a significant decrease in mean uterine horn diameter of animals in group Ⅱ and group Ⅳ after the treatment reading 8.21±0.710 mm and 12.08±2.054 mm, respectively. This shows that inclusion of misoprostol in these two groups helped in uterine contraction and evacuation of pus from uterus, thereby decreasing the mean diameter of uterine lumen Pre-treatment mean uterine wall thickness (mm) of animals in group Ⅰ, Ⅱ, Ⅲ and Ⅳ were 6.265±0.4258, 5.243±1.4510, 6.077±2.0870 and 5.468±0.2434, respectively. These values indicate thickened uterine wall compared to normal healthy uterine wall thickness of 0.17±0.01 mm (Veiga et al., 2017) [42] . Similar observations of thickened uterine wall in pyometra affected female dogs were observed by Vidya (2019) [44] and Unnikrishnan (2018) [41] , who observed 6.0±0.44 mm and 5.79±0.15 mm, respectively. It was noticed that there was a decrease in mean uterine wall thickness after the end of treatment on day 14 in all groups, as there was usage of antiprogestins in all groups which altered the progesterone dominance on uterine wall thereby decreasing its thickness. Even the usage of anti progestins could manage the inflammatory abnormalities of endometrium in pyometra affected female dogs (Gobello et al., 2003) [8] . Group II (aglepristone plus misoprostol) showed superior efficacy, likely due to the injectable route's faster absorption and aglepristone's high progesterone receptor affinity (Hoffmann, 2000) [16] . Misoprostol's enhancement of uterine contractions and cervical relaxation facilitated pus evacuation (Danielsson, 1999) [3] . Group IV's lower efficacy may reflect mifepristone's mixed agonist/antagonist properties and oral administration challenges in vomiting dogs (Jurka, 2010) [21] . Significant reductions in globulin levels and uterine lumen diameter in Group II align with prior studies (Chinnu, 2016; Vidya, 2019) [2,44] , indicating effective inflammation reduction and uterine evacuation. The small sample size (n = 24) limits generalizability. The lack of significant changes in some haematological parameters may reflect chronic disease adaptations. Larger, longitudinal studies are needed to optimize dosing protocols and confirm findings.

Conclusion

Injectable aglepristone combined with misoprostol offers a highly effective medical treatment for canine pyometra, significantly reducing uterine lumen diameter, globulin levels, and recovery time while preserving fertility. This approach minimizes surgical risks and economic burdens, making it a viable alternative to OHE. Further studies with larger populations are recommended.

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