Medroxyprogesterone Acetate (MPA) is a synthetic progestin commonly used in veterinary medicine, including equine practice. It is often administered to manage reproductive behavior and estrus-related issues in mares. MPA acts by mimicking the effects of the natural hormone progesterone, thereby influencing the reproductive cycle and behavior of horses. Its use extends to controlling estrus in performance horses to improve focus and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetics, effects, and applications of Medroxyprogesterone Acetate in equine management.
Zeng Z, Jiang X, Li X, Wells A, Luo Y, Neapolitan R.By the 1990s it became popular for women to use hormone therapy (HT) to ease menopause symptoms. Bioidentical estrogen and progesterone are supplements whose molecular structures are identical to what is made in the human body, while synthetic supplements are ones whose structures are not. After the Women's Health Initiative found that the combined use of the synthetics conjugated equine estrogen (CEE) and medroxyprogesterone acetate (MPA) increased breast cancer risk, prescriptions for synthetic HT declined considerably. Since then there has been an increased interest in bioidentical HT; toda...
Vardy MD, Gardner TR, Cosman F, Scotti RJ, Mikhail MS, Preiss-Bloom AO, Williams JK, Cline JM, Lindsay R.The purpose of this study was to determine effects of ovariectomy (OVX) and conjugated equine estrogens plus medroxyprogesterone acetate (CEE/MPA), or ethinyl estradiol plus norethindrone acetate (EE/NA) on biomechanics of uterosacral (USL) and round (RL) ligaments in postmenopausal (PMP) monkeys. Methods: This was a randomized, triple blind, placebo-controlled study. OVX monkeys received 12 months no treatment (Pbo) (n = 19), CEE/MPA (n = 19), or EE/NA (n = 21). USL and RL step strains and stress-relaxation data were curve-fitted, giving strain-dependent tensile modulus (TM) from 0% to 30%. R...
Simon JA, Liu JH, Speroff L, Shumel BS, Symons JP.The purpose of this study was to compare the effects on vaginal bleeding patterns of continuous combined hormone replacement therapy with norethindrone acetate and ethinyl estradiol versus conjugated equine estrogens and medroxyprogesterone acetate. Methods: Three hundred fifty-seven postmenopausal women were selected randomly (in a blinded manner) to 12 months of treatment with 1 mg norethindrone acetate/5 microg ethinyl estradiol, placebo, or open-label 0.625 mg conjugated equine estrogens/2.5 mg medroxyprogesterone acetate (conjugated equine estrogens/medroxyprogesterone acetate [CEE/MPA]; ...
Lehnert M, de Giuli R, Kunke K, Emerson S, Dalton WS, Salmon SE.The purpose of this study was to evaluate to what extent the ability of various chemosensitisers (CS) to reverse P-glycoprotein-associated multidrug resistance (MDR) is reduced when tested in physiological serum protein concentrations. Utilising drug sensitivity and accumulation assays, the CS were tested in medium containing 10% fetal bovine serum and in 100% horse or human serum. Two RPMI 8226 human myeloma sublines were used which express different levels of P-glycoprotein. The CS were tested at various concentrations, including clinically achievable blood levels. When using the CS at high ...
Williams JK, Honoré EK, Washburn SA, Clarkson TB.We attempted to determine whether continuous and cyclic medroxyprogesterone acetate modulates the effects of estrogen on dilation of atherosclerotic coronary arteries in surgically postmenopausal female monkeys. Background: Estrogen replacement in postmenopausal women preserves normal dilator responses of atherosclerotic coronary arteries. The effects of progestins on coronary artery reactivity have not been determined. Methods: Repeated quantitative coronary angiography was used to study the effects after 1 month of 1) no hormone replacement (control) or oral administration of 2) continuous c...
Williams JK, Honoré EK, Washburn SA, Clarkson TB.We attempted to determine whether continuous and cyclic medroxyprogesterone acetate modulates the effects of estrogen on dilation of atherosclerotic coronary arteries in surgically postmenopausal female monkeys. Background: Estrogen replacement in postmenopausal women preserves normal dilator responses of atherosclerotic coronary arteries. The effects of progestins on coronary artery reactivity have not been determined. Methods: Repeated quantitative coronary angiography was used to study the effects after 1 month of 1) no hormone replacement (control) or oral administration of 2) continuous c...
Vardy MD, Gardner TR, Cosman F, Scotti RJ, Mikhail MS, Preiss-Bloom AO, Williams JK, Cline JM, Lindsay R.The purpose of this study was to determine effects of ovariectomy (OVX) and conjugated equine estrogens plus medroxyprogesterone acetate (CEE/MPA), or ethinyl estradiol plus norethindrone acetate (EE/NA) on biomechanics of uterosacral (USL) and round (RL) ligaments in postmenopausal (PMP) monkeys. Methods: This was a randomized, triple blind, placebo-controlled study. OVX monkeys received 12 months no treatment (Pbo) (n = 19), CEE/MPA (n = 19), or EE/NA (n = 21). USL and RL step strains and stress-relaxation data were curve-fitted, giving strain-dependent tensile modulus (TM) from 0% to 30%. R...
Lehnert M, de Giuli R, Kunke K, Emerson S, Dalton WS, Salmon SE.The purpose of this study was to evaluate to what extent the ability of various chemosensitisers (CS) to reverse P-glycoprotein-associated multidrug resistance (MDR) is reduced when tested in physiological serum protein concentrations. Utilising drug sensitivity and accumulation assays, the CS were tested in medium containing 10% fetal bovine serum and in 100% horse or human serum. Two RPMI 8226 human myeloma sublines were used which express different levels of P-glycoprotein. The CS were tested at various concentrations, including clinically achievable blood levels. When using the CS at high ...
Simon JA, Liu JH, Speroff L, Shumel BS, Symons JP.The purpose of this study was to compare the effects on vaginal bleeding patterns of continuous combined hormone replacement therapy with norethindrone acetate and ethinyl estradiol versus conjugated equine estrogens and medroxyprogesterone acetate. Methods: Three hundred fifty-seven postmenopausal women were selected randomly (in a blinded manner) to 12 months of treatment with 1 mg norethindrone acetate/5 microg ethinyl estradiol, placebo, or open-label 0.625 mg conjugated equine estrogens/2.5 mg medroxyprogesterone acetate (conjugated equine estrogens/medroxyprogesterone acetate [CEE/MPA]; ...
Zeng Z, Jiang X, Li X, Wells A, Luo Y, Neapolitan R.By the 1990s it became popular for women to use hormone therapy (HT) to ease menopause symptoms. Bioidentical estrogen and progesterone are supplements whose molecular structures are identical to what is made in the human body, while synthetic supplements are ones whose structures are not. After the Women's Health Initiative found that the combined use of the synthetics conjugated equine estrogen (CEE) and medroxyprogesterone acetate (MPA) increased breast cancer risk, prescriptions for synthetic HT declined considerably. Since then there has been an increased interest in bioidentical HT; toda...
