Efficacy, safety and interval from end of treatment to estrus in cats treated with an ultra-low dose megestrol acetate protocol for suppression of reproductive activity

Pereira, Maria (author), Grassi, Anna (author), Zakošek, Maja (author), Contato, Giulia (author), Dal Ponte, Giada (author), Ghezzo, Anna (author), De Cramer, Kurt G. M. (author), Romagnoli, Stefano E. (author)

Cat breeders need safe, predictable and fully reversible temporary control of reproduction in queens. Megestrol acetate (MA), a short-acting progestogen was investigated in this study designed to determine whether low-dose treatment is both effective and safe in cats for periods up to 6 months. Twenty-eight queens were treated orally with 11.5 μg/kg/day of MA for one to six months. A physical examination, vaginal cytology, and reproductive ultrasound were performed before, during and after treatment, whilst urinalysis and hematological/biochemical tests, including progesterone assay, were performed before and after treatment. MA suppressed reproductive function effectively in 27/28 queens. Transient mammary and uterine hyperplasia were detected in four (14 %) and three (11 %) queens, respectively, treated for more than four months, without associated clinical signs. Pyometra was observed in only one queen following her first estrus cycle post-treatment. Significant but reversible weight gain was observed in 85 % of the animals. The resumption of cyclicity occurred on average 6 weeks after the end of treatment but was influenced by the duration of treatment and seasonality. An ultra-low dose MA treatment was effective in suppressing estrus in queens treated up to 6 months. Close monitoring should be paid to queens treated for longer than 4 months as the incidence of side effects, albeit minor and manageable, increases thereafter. Mammary gland assessment and progesterone assay are indispensable before treatment. Fertility is preserved, making MA a valuable option for temporary control of reproductive activity in queens, who otherwise cycle continuously leading to both unwanted behavior and pregnancies.

• Language: English
• Keywords: cats, reproduction control, progestogens, megestrol acetate, contraception
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: VF - Veterinary Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 9 str.
• Numbering: Vol. 246, art. 117530
• PID: 20.500.12556/RUL-170892
• UDC: 618.2/.7:636.09
• ISSN on article: 1879-3231
• DOI: 10.1016/j.theriogenology.2025.117530
• COBISS.SI-ID: 243038467
• Publication date in RUL: 21.07.2025

Record is a part of a journal

• Title: Theriogenology
• Shortened title: Theriogenology
• Publisher: Elsevier Inc.
• ISSN: 1879-3231
• COBISS.SI-ID: 71159043

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: mačke, nadzor reprodukcije, progestageni, megestrol acetat, kontracepcija