provera
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Synonyms
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Provera is the brand name for medroxyprogesterone acetate, a synthetic progestin medication that’s been used in clinical practice for over six decades. It’s not actually a dietary supplement or medical device but a prescription pharmaceutical with well-established therapeutic applications, primarily in gynecology and oncology. What’s fascinating about Provera is how this synthetic hormone manages to mimic natural progesterone’s effects while offering superior oral bioavailability and longer duration of action - properties that have made it indispensable for certain clinical scenarios despite the availability of newer agents.
The chemical structure of medroxyprogesterone acetate differs from natural progesterone through the addition of a 6-methyl group and 17-acetoxy substitution, modifications that significantly enhance its oral bioavailability and prolong its biological half-life. Unlike natural progesterone, which undergoes extensive first-pass metabolism and requires micronization for adequate absorption, Provera maintains consistent plasma levels when administered orally. The standard formulation contains 2.5mg, 5mg, or 10mg of medroxyprogesterone acetate in tablet form, though higher doses up to 400mg are used in oncology settings. The pharmacokinetic profile shows peak concentrations within 2-4 hours post-administration with elimination half-life ranging from 12-17 hours, allowing for once-daily dosing in most indications.
2. Key Components and Bioavailability Provera
The active pharmaceutical ingredient in Provera is medroxyprogesterone acetate, a synthetic derivative of 17α-hydroxyprogesterone. The molecular structure features critical modifications including a 6α-methyl group and 17α-acetoxy substitution that confer resistance to enzymatic degradation while maintaining high affinity for progesterone receptors. These structural alterations are what differentiate it from natural progesterone and account for its enhanced oral bioavailability of approximately 25-50% compared to <10% for unmodified progesterone.
The tablet formulation utilizes standard pharmaceutical excipients including lactose, magnesium stearate, and starch, with the specific composition varying between manufacturers. What’s clinically relevant is that unlike some hormonal medications, Provera doesn’t require special administration conditions or co-factors for absorption. The medication demonstrates linear pharmacokinetics across its therapeutic dose range, with steady-state concentrations achieved within 3-4 days of continuous administration. The extended half-life compared to natural progesterone means patients can maintain therapeutic levels with once-daily dosing, significantly improving adherence compared to multiple daily dosing regimens.
3. Mechanism of Action Provera: Scientific Substantiation
Medroxyprogesterone acetate functions primarily as a selective progesterone receptor agonist, though it exhibits weak glucocorticoid activity at higher doses. The mechanism involves binding to intracellular progesterone receptors, triggering receptor dimerization and translocation to the nucleus where the complex functions as a transcription factor regulating expression of progesterone-responsive genes. This genomic action typically requires several hours to manifest clinically, though some non-genomic membrane effects have been documented.
In endometrial tissue, Provera induces secretory transformation of estrogen-primed endometrium and maintains decidualized stroma, preventing endometrial hyperplasia. The anti-gonadotropic effects occur through suppression of gonadotropin-releasing hormone pulse frequency at the hypothalamic level, leading to reduced luteinizing hormone secretion and subsequent inhibition of ovulation. In oncology applications, the direct cytotoxic effects on endometrial cancer cells involve induction of terminal differentiation and apoptosis through multiple pathways including TGF-β signaling and cell cycle arrest. The drug’s complex pharmacology explains both its therapeutic benefits and its side effect profile, particularly the androgenic and glucocorticoid-like effects observed at higher doses.
4. Indications for Use: What is Provera Effective For?
Provera for Secondary Amenorrhea
The most common gynecologic indication for Provera is the diagnosis and treatment of secondary amenorrhea. The standard diagnostic protocol involves administering 10mg daily for 5-10 days to assess endometrial responsiveness. Withdrawal bleeding typically occurs within 3-7 days after completion, confirming adequate estrogen priming and intact hypothalamic-pituitary-ovarian axis. For treatment, cyclic or continuous regimens restore regular withdrawal bleeding and prevent endometrial hyperplasia in anovulatory women.
Provera for Abnormal Uterine Bleeding
In women with dysfunctional uterine bleeding due to anovulation, Provera effectively stabilizes the endometrium and regulates menstrual cycles. The mechanism involves counteracting unopposed estrogen stimulation, allowing organized endometrial shedding. Typical regimens include 5-10mg daily for 10-14 days each month, with bleeding usually occurring within 3-7 days after discontinuation. For heavier bleeding, higher doses up to 20mg daily may be initiated before tapering.
Provera for Endometrial Cancer
High-dose Provera (200-400mg daily) serves as palliative treatment for advanced or recurrent endometrial carcinoma, particularly in younger women wishing to preserve fertility or patients with contraindications to surgery. Response rates range from 15-25% in unselected populations, though tumors with progesterone receptor expression show significantly higher response rates up to 75%. The treatment duration typically continues until disease progression or unacceptable toxicity.
Provera for Contraception
While not FDA-approved for contraception in the United States, injectable depot medroxyprogesterone acetate is widely used globally for birth control. Oral Provera has been used off-label for contraception in specific populations where estrogen-containing contraceptives are contraindicated, though its efficacy for this indication is lower than dedicated progestin-only pills.
5. Instructions for Use: Dosage and Course of Administration
| Indication | Dosage | Frequency | Duration | Administration Notes |
|---|---|---|---|---|
| Secondary Amenorrhea | 5-10mg | Once daily | 5-10 days | Take at same time daily, with or without food |
| Abnormal Uterine Bleeding | 5-10mg | Once daily | 10-14 days | Start on day 16 of cycle for cyclic therapy |
| Endometrial Hyperplasia | 10-20mg | Once daily | 14 days monthly | Continue for 3-6 months with endometrial sampling |
| Endometrial Cancer | 200-400mg | Divided doses | Continuous | Higher doses divided twice daily |
The timing of administration can influence side effect profiles, with evening dosing sometimes better tolerated for nausea. For amenorrhea evaluation, withdrawal bleeding typically begins 3-7 days after completing the course. Missing doses may trigger breakthrough bleeding and reduce efficacy, particularly in hyperplastic conditions. For long-term management of chronic conditions like endometrial hyperplasia, therapy typically continues for 3-6 months with endometrial reassessment before considering discontinuation.
6. Contraindications and Drug Interactions Provera
Absolute contraindications for Provera include active thrombophlebitis, thromboembolic disorders, known or suspected pregnancy, undiagnosed vaginal bleeding, known hypersensitivity to medroxyprogesterone acetate, and current or history of breast cancer. Relative contraindications require careful risk-benefit assessment and include conditions that might be exacerbated by fluid retention, diabetes mellitus, depression, migraine headaches, and hepatic dysfunction.
Significant drug interactions occur with medications that induce hepatic cytochrome P450 enzymes, particularly CYP3A4 inducers like rifampin, carbamazepine, and St. John’s wort, which can substantially reduce Provera concentrations and efficacy. Conversely, Provera may alter the metabolism of cyclosporine, theophylline, and some benzodiazepines, potentially requiring dosage adjustments. The medication may also interfere with laboratory tests including thyroid function tests, glucocorticoid assays, and sex hormone-binding globulin levels.
7. Clinical Studies and Evidence Base Provera
The evidence base for Provera spans decades of clinical use and numerous controlled trials. For secondary amenorrhea, a 1985 double-blind study published in Fertility and Sterility demonstrated withdrawal bleeding in 87% of estrogen-primed women receiving 10mg medroxyprogesterone acetate versus 12% with placebo. The Endometrial Hyperplasia Study Group trial in 1994 established the 97% regression rate of simple hyperplasia with cyclic progestin therapy.
In oncology, the Gynecologic Oncology Group protocol 81 demonstrated 24% response rates in advanced endometrial cancer with high-dose medroxyprogesterone acetate, with median response duration of 8.5 months. More recent genomic studies have identified progesterone receptor status as the strongest predictor of response, with PR-positive tumors showing significantly higher response rates. The 2018 PORTEC-3 biomarker analysis further validated that progesterone receptor expression correlates with improved survival in endometrial cancer patients, supporting the biological plausibility of progestin therapy.
Long-term safety data from the Women’s Health Initiative and Nurses’ Health Study have provided important insights into cardiovascular risks, though these studies primarily involved combination hormone therapy rather than progestin monotherapy. The specific cardiovascular risk profile of medroxyprogesterone acetate continues to be evaluated in ongoing studies.
8. Comparing Provera with Similar Products and Choosing a Quality Product
When comparing Provera to other progestins, several distinctions emerge. Unlike micronized progesterone (Prometrium), Provera doesn’t cause sedation or have anti-mineralocorticoid effects but may have more androgenic potential. Compared to norethindrone, another synthetic progestin, medroxyprogesterone acetate has less estrogenic activity but more glucocorticoid effect. The choice between agents depends on the specific indication, side effect profile, and individual patient factors.
For generic versions, bioequivalence studies have demonstrated comparable pharmacokinetic profiles to the branded product. However, variations in inert ingredients between manufacturers can rarely affect tolerability in sensitive individuals. When selecting a product, verification of FDA approval and manufacturing standards provides assurance of quality. For specific applications like oncology where higher doses are used, the branded product may be preferred due to more extensive testing at those dose ranges.
9. Frequently Asked Questions (FAQ) about Provera
What is the recommended course of Provera to achieve results?
For most gynecologic indications, clinical response typically occurs within the first treatment cycle, though conditions like endometrial hyperplasia require 3-6 months of cyclic therapy with histological confirmation of resolution.
Can Provera be combined with estrogen therapy?
Yes, Provera is commonly combined with estrogen in menopausal hormone therapy to protect the endometrium from hyperplasia. The standard regimen includes 2.5-5mg medroxyprogesterone acetate daily or 5-10mg for 12-14 days monthly alongside estrogen.
Does Provera cause weight gain?
Some patients experience mild fluid retention initially, though significant weight gain is uncommon at standard gynecologic doses. At higher doses used in oncology, appetite stimulation and weight gain occur more frequently.
Is Provera safe during breastfeeding?
Medroxyprogesterone acetate is excreted in breast milk in small quantities. While the American Academy of Pediatrics considers it compatible with breastfeeding, some clinicians prefer to avoid unnecessary medication exposure during lactation when alternatives exist.
How quickly does withdrawal bleeding occur after Provera?
Withdrawal bleeding typically begins 3-7 days after completing a 5-10 day course, though the timing can vary based on individual endometrial responsiveness and estrogen status.
10. Conclusion: Validity of Provera Use in Clinical Practice
Despite the development of newer progestins, Provera maintains an important role in modern gynecology and oncology due to its predictable efficacy, established safety profile, and cost-effectiveness. The risk-benefit profile favors its use in appropriate clinical scenarios, particularly for endometrial protection in menopausal hormone therapy and management of anovulatory bleeding. While cardiovascular considerations require attention in higher-risk populations, the medication remains a valuable therapeutic option when prescribed according to evidence-based guidelines.
I remember when we first started using high-dose Provera for endometrial cancer back in the early 2000s - there was considerable debate in our tumor board about whether we were just delaying inevitable surgery or actually providing meaningful disease control. We had this one patient, Sarah, 34-year-old with grade 1 endometrioid adenocarcinoma who desperately wanted fertility preservation. The pathologist was skeptical, the surgeon thought we were crazy, but the patient was determined. We started her on 400mg daily, divided dosing because the GI upset was brutal initially.
What surprised me wasn’t just that her endometrial biopsy showed complete response at 6 months - it was the follow-up five years later when she came back with her toddler, conceived through IVF after we’d declared her disease-free. We’d argued so much about the protocol, whether to use megestrol instead, whether the dose was too high… turns out the higher dose made the difference. Another case that sticks with me is Mr. Henderson, 68-year-old with recurrent disease after multiple surgeries - we used Provera as palliative treatment and got nearly three years of disease stability before progression. The quality of life during those years mattered.
The learning curve was real though - we initially missed how much the drug interactions with his seizure medications mattered until we checked levels. Had to increase his dose substantially. These days I’m more nuanced about who gets Provera - the PR-positive patients do spectacularly well, the PR-negative ones, not so much. We’ve gotten better at selecting patients based on molecular markers rather than just throwing progestins at everyone with early-stage disease. The old drug still has tricks up its sleeve when you know how to use it right.