MEDROXYPROGESTERONE ACETATE
Chemistry - A synthetic progestin, medroxyprogesterone acetate (MPA) occurs as an odorless, white to off-white, crystalline powder. It is insoluble in water and sparingly soluble in alcohol. Ithas a melting range of 200°-210°C. Medroxyprogesterone acetate may also be known as MPA,
MAP, acetoxymethylprogesterone or methylacetoxyprogesterone.
MPA tablets should be stored in well-closed containers at room temperature.
ACTH and cortisol release. MPA is anti-estrogenic and will also decrease plasma testosteronelevels in male humans and dogs.
MPA has antineoplastic activity against endometrial carcinoma and renal carcinoma (efficacy indoubt) in human patients. The mechanism for this activity is not known.
Uses, Indications - In cats, MPA has been used when either castration is ineffective or undesirableto treat sexually dimorphic behavior problems such as roaming, inter-male aggressive behaviors, spraying, mounting, etc. MPA has also been used as a tranquilizing agent to treat syndromes suchas feline psychogenic dermatitis and alopecia, but treatment with "true" tranquilizing agents maybe preferable.
In humans, parenteral MPA has been used as a long-acting contraceptive in females, to decreasesexually deviant behavior in males and as an antineoplastic agent for some carcinomas (see
Pharmacology section above). Oral MPA is used in human females to treat secondary amenorrheaand to treat abnormal uterine bleeding secondary to hormone imbalances.
MPA has contraceptive activity for at least 3 months.
Contraindications/Precautions - Progestagen therapy can cause serious adverse effects (seebelow). Safer alternative treatments should be considered when possible, otherwise, weigh thepotential risks versus benefits before instituting therapy. Many clinicians believe that progestagensare grossly overused.
Because this drug can suppress adrenal function, exogenous steroids may need to be administeredif the patient is stressed (e.g., surgery, trauma).
Overdosage - No reports or information was located on inadvertent overdosage with this agent.
Refer to the Adverse effects section above.
Drug/Laboratory Interactions - In humans, progestins in combination with estrogens (e.g., oralcontraceptives) have been demonstrated to increase thyroxine-binding globulin (TBG) with resultant increases in total circulating thyroid hormone. Decreased T3 resin uptake also occurs, butfree T4 levels are unaltered. Liver function tests may also be altered.
The manufacturer recommends notifying the pathologist of patient medroxyprogesterone exposure when submitting relevant specimens.
MAP, acetoxymethylprogesterone or methylacetoxyprogesterone.
Storage, Stability, Compatibility
Medroxyprogesterone acetate suspensions for injectionshould be stored at room temperature (15-30°C); avoid freezing and temperatures above 40°C.MPA tablets should be stored in well-closed containers at room temperature.
Pharmacology - MEDROXYPROGESTERONE ACETATE
Progestins are primarily produced endogenously by the corpus luteum. Theytransform proliferative endometrium to secretory endometrium, enhance myometrium hypertrophyand inhibit spontaneous uterine contraction. Progestins have a dose-dependent inhibitory effect onthe secretion of pituitary gonadotropins and can have an anti-insulin effect. Medroxyprogesteronehas exhibited a pronounced adrenocorticoid effect in animals (species not listed) and can suppressACTH and cortisol release. MPA is anti-estrogenic and will also decrease plasma testosteronelevels in male humans and dogs.
MPA has antineoplastic activity against endometrial carcinoma and renal carcinoma (efficacy indoubt) in human patients. The mechanism for this activity is not known.
Uses, Indications - In cats, MPA has been used when either castration is ineffective or undesirableto treat sexually dimorphic behavior problems such as roaming, inter-male aggressive behaviors, spraying, mounting, etc. MPA has also been used as a tranquilizing agent to treat syndromes suchas feline psychogenic dermatitis and alopecia, but treatment with "true" tranquilizing agents maybe preferable.
In humans, parenteral MPA has been used as a long-acting contraceptive in females, to decreasesexually deviant behavior in males and as an antineoplastic agent for some carcinomas (see
Pharmacology section above). Oral MPA is used in human females to treat secondary amenorrheaand to treat abnormal uterine bleeding secondary to hormone imbalances.
Pharmacokinetics - MEDROXYPROGESTERONE ACETATE
No specific pharmacokinetic parameters in veterinary species were located forthis drug. It has been reported (Beaver 1989) that injectable MPA has an approximate duration ofaction of 30 days when used to treat behavior disorders in cats. When administered IM to women,MPA has contraceptive activity for at least 3 months.
Contraindications/Precautions - Progestagen therapy can cause serious adverse effects (seebelow). Safer alternative treatments should be considered when possible, otherwise, weigh thepotential risks versus benefits before instituting therapy. Many clinicians believe that progestagensare grossly overused.
Because this drug can suppress adrenal function, exogenous steroids may need to be administeredif the patient is stressed (e.g., surgery, trauma).
Adverse Effects, Warnings
If MPA is administered subcutaneously, permanent local alopecia, atrophy and depigmentation may occur. If injecting SQ, it is recommended to use the inguinal areato avoid these manifestations. Adverse reactions that are possible in dogs and cats include increasedappetite and/or thirst, depression, lethargy, personality changes, adrenocortical depression, mammary changes (including enlargement, milk production, and neoplasms), diabetes mellitus, pyometra and temporary inhibition of spermatogenesis. In dogs, acromegaly and increased growthhormone levels have been seen when used in patients with diabetes mellitus.Overdosage - No reports or information was located on inadvertent overdosage with this agent.
Refer to the Adverse effects section above.
Drug Interactions
None reported. A potential interaction exists with Rifampin, which maydecrease progestin activity if administered concomitantly. This is presumably due to microsomalenzyme induction with resultant increase in progestin metabolism. The clinical significance of thispotential interaction is unknown.Drug/Laboratory Interactions - In humans, progestins in combination with estrogens (e.g., oralcontraceptives) have been demonstrated to increase thyroxine-binding globulin (TBG) with resultant increases in total circulating thyroid hormone. Decreased T3 resin uptake also occurs, butfree T4 levels are unaltered. Liver function tests may also be altered.
The manufacturer recommends notifying the pathologist of patient medroxyprogesterone exposure when submitting relevant specimens.