Susten is commonly used to manage symptoms and conditions related to hormonal variation, offering supportive relief across key domains of women’s health. Its use is considered relevant for managing symptoms of menopause and for inducing a period in women who have amenorrhea.

The medication is applied in addressing symptom clusters that may become intense or disruptive, relevant for managing symptoms that interfere with daily comfort. These include conditions where symptoms may intensify temporarily, and situations where symptoms create noticeable physiological strain.

Symptomatic Support

The general benefit is that the treatment provides support that helps ease the overall symptom burden during periods of heightened discomfort. This includes supporting the management of absent or irregular periods, symptoms related to menopause (like hot flashes), and providing assistance during fertility protocols.

“The primary benefit is that it helps maintain a sense of stability when symptoms are more noticeable.”

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Quick Fact: Symptomatic Support

Susten is commonly used to help with symptoms related to heightened physiological activity, contributing to improved comfort during periods of heightened symptoms.

Regulatory References

1. NIH MedlinePlus overview

Who Can and Cannot Use Susten? Official Regulatory Information

The eligibility for Susten (Micronized Progesterone) is strictly defined by regulatory documents, focusing on established use and mandatory exclusions.

Populations for Whom Use is Contraindicated

Susten must not be used by individuals presenting with specific conditions, as these are absolute contraindications stated in regulatory labels:

• Active or history of arterial or venous thromboembolic disorders (e.g., blood clots, stroke).
• Known or suspected hormone-dependent malignant tumors (e.g., breast or genital tract cancer).
• Severe hepatic impairment or active liver disease.
• Undiagnosed abnormal genital bleeding or confirmed missed abortion.
• Known hypersensitivity to progesterone or any excipients.

Age and Physiological Restrictions

Population	Regulatory Status
Adult Women	Established use for specific indications (e.g., ART support).
Pediatric	Use is not established or not indicated.
Geriatric	Use is not established (insufficient clinical data).
Lactation	Not recommended or contraindicated while breastfeeding.

Use requires caution and close monitoring in patients with a history of depression, as well as conditions potentially aggravated by fluid retention, such as epilepsy, asthma, hypertension, or renal impairment, as defined in the official prescribing information.

Interactions with other medicines and products

The interaction profile of micronized progesterone is primarily defined by its effects on metabolic pathways and specific administration constraints documented in official regulatory labeling.

Drug-Drug Interactions (Metabolic and Transporter): Co-administration with medicines known as strong CYP3A4 inducers (such as Rifampicin or anti-seizure medications) may increase the clearance of progesterone, leading to decreased systemic exposure. Conversely, co-administration with strong CYP3A4 inhibitors (such as Ketoconazole or certain HIV treatments) may decrease the elimination of progesterone, resulting in increased plasma concentrations. Progesterone is also documented to inhibit the P-glycoprotein (P-gp) efflux transporter, an interaction that may increase the systemic exposure of co-administered P-gp substrate medicines.

Pharmacodynamic Interactions and Efficacy: The medicine’s efficacy may be compromised when co-administered with Ulipristal acetate, a selective progesterone receptor modulator. Official labeling also notes that progesterone may modify the effects of certain medications, including anticoagulants and anti-diabetic medicines, where modification of the co-administered drug’s dosage may be required. The herbal supplement St. John’s wort is listed as a documented inducer that may reduce the medicine's exposure.

Product and Timing Constraints: For the oral capsule, co-ingestion with high-fat food is documented to increase the bioavailability of the medicine. Due to the potential for altered absorption, co-administration of the vaginal formulation with other local vaginal products (such as lubricants or antifungals) is not recommended as an official restriction.

How Susten Works

Susten, a micronized formulation of progesterone, functions as an agonist by selectively binding to and activating the intracellular progesterone receptor (PR). This binding facilitates the receptor's translocation into the cell nucleus. Once internalized, the PR complex acts as a transcription factor, modulating the rate of gene expression by binding to specific DNA sequences known as Progesterone Response Elements (PREs). This action initiates or suppresses the transcription of target genes to regulate cellular protein synthesis.

At the system level, the resulting increase in circulating progesterone influences the hypothalamic-pituitary-gonadal (HPG) axis through negative feedback, which modulates the release of gonadotropins such as Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). In reproductive tissues, this mechanism drives specific cellular changes, including the induction of secretory differentiation and anti-proliferative effects within the endometrium. This tissue-level consequence shifts the endometrium from a proliferative to a secretory phase, initiating stromal edema and vascularization.

How Susten is Used: Official Administration Guidelines

The usage of Susten (micronized progesterone) is strictly governed by regulatory instructions detailing the specific route, dosage, frequency, and duration of administration. This medicine is formally approved for delivery through three primary routes: Oral soft gelatin capsules, Vaginal inserts or capsules, and Intramuscular (IM) injection of an oil solution, with the selected route depending on the therapeutic regimen.

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Official Dosing and Frequency Patterns

The required dose and schedule vary significantly based on the context of use:

• Cyclic Dosing: For contexts like preventing endometrial hyperplasia in HRT or treating secondary amenorrhea, the regimen is often cyclic, involving a specific dose (e.g., 200 mg or 400 mg) taken once daily for a fixed duration, typically 10 to 12 consecutive days per cycle.
• Divided Daily Dosing: In scenarios such as luteal phase support during Assisted Reproductive Technology (ART), dosing is often divided, requiring the capsule or insert to be administered two to three times daily for a specified period.

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Administration Conditions and Constraints

Official labels define precise instructions regarding the timing of administration. The oral form is typically directed to be taken at bedtime (qHS) and, for certain indications, with food to manage absorption and mitigate the possibility of sedation. Capsules must be swallowed whole. If a dose is missed, official instructions generally mandate skipping the missed dose and resuming the schedule at the next designated time; doubling doses is prohibited. Furthermore, use is formally contraindicated in patients with severe hepatic impairment.

Research Evidence / Overview of Studies for Susten (Micronized Progesterone)

This overview summarizes the official research evidence, including key trials and reviews, that regulators rely on to describe the studied uses of Susten (micronized progesterone). This information details the types of studies conducted and what their findings describe, without offering any clinical advice or recommendations.

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Evidence for Use in Assisted Reproductive Technology (ART)

Research was studied for its use exploring the luteal phase in assisted reproductive technology (ART), such as In Vitro Fertilization (IVF), and is based on a large number of Randomized Controlled Trials (RCTs) and comprehensive meta-analyses. This type of research was studied for women undergoing stimulated cycles to explore how the addition of the hormone was observed in these protocols.

Studies monitored high-level outcomes related to the establishment of pregnancy. Researchers examined outcomes such as the Live Birth Rate (LBR) and the Clinical Pregnancy Rate (CPR). Findings describe patterns observed when progesterone was administered compared to a control or placebo, relevant in evidence describing how hormonal support is evaluated in these protocols. Research also explores various forms of progesterone (including oral, vaginal, and injectable) to explore whether different delivery methods were associated with similar reported outcomes regarding Clinical Pregnancy Rate (CPR) and Live Birth Rate (LBR).

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Evidence for Managing Menopausal Symptoms

Research was studied for its use exploring how symptoms change over time, particularly vasomotor symptoms (VMS) like hot flashes and night sweats, and has primarily been conducted through short-term, placebo-controlled Randomized Controlled Trials (RCTs). The research examined outcomes related to physical discomfort, such as the frequency and intensity of hot flashes using patient-reported outcomes describing perceived discomfort. Studies report how symptoms evolved in the groups receiving progesterone compared to those receiving a placebo.

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What is Still Uncertain About the Research for Susten

Evidence highlights what is known, and what is still uncertain, across the entire research landscape for micronized progesterone. For VMS, the core efficacy trials typically monitor effects only for short-term intervals (e.g., three months), meaning long-term effects are not well characterized based on the primary evidence base. Data for certain groups remain insufficient, as many RCTs include generally healthy populations, and findings for women with certain comorbidities or for pediatric/older adult groups are still emerging.

Key Studies & References Progesterone Drug Overview (NIH MedlinePlus)

Common questions about Susten (FAQ)

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Q: What is Susten used for and what are its main indications?

According to official product information, Susten (which contains the active substance progesterone) is used in women with infertility due to luteal phase deficiency. It is also indicated for the prevention of threatened or recurrent miscarriage and in assisted reproductive technology (ART) programs, particularly in cases of embryo transfer. Official documents state its purpose is to supplement the body's natural progesterone levels.

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Q: What is progesterone and why is it important?

Progesterone is a naturally occurring female hormone that plays a crucial role in regulating the menstrual cycle and supporting the early stages of pregnancy. Regulatory documents indicate that when the body's progesterone levels are insufficient (a condition called luteal phase deficiency), supplementation with this type of medicine may be considered as part of a treatment plan to prepare the uterine lining.

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Q: Does Susten affect the menstrual cycle or ovulation?

Susten, as a progesterone supplement, can affect the timing of the menstrual cycle. According to regulatory sources, if the treatment is stopped, a withdrawal bleed (similar to a period) often occurs within a few days. Label information indicates its primary role is to support the uterine lining, rather than directly causing ovulation.

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Q: Is Susten safe to use during pregnancy?

Regulatory documents indicate that Susten is specifically used and may be considered appropriate to support early pregnancy in certain situations, such as threatened or recurrent miscarriage and as part of assisted reproduction techniques. Official product information states it is generally used under medical supervision for these specific indications and is not intended for use in all pregnancies.

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Q: What is the available form or route of administration for Susten?

The official product information for Susten indicates that it is available as a soft gelatin capsule that can be used via the vaginal or oral route, depending on the specific medical indication and doctor's instruction. The route of administration is specified in the regulatory sources to optimize the absorption of the progesterone.

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Q: Can Susten be used for hormone replacement therapy (HRT)?

Regulatory documents state that Susten is not primarily indicated for standard Hormone Replacement Therapy (HRT) to treat general menopausal symptoms. Its specific indications revolve around luteal support and the prevention of certain types of miscarriage in women. While progesterone is a component of some HRT, this specific product is targeted for fertility-related uses.

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Q: What should I do if I miss a dose of Susten?

Official product information emphasizes that if a dose of Susten is missed, it is advised to contact a healthcare provider immediately for specific instructions. Regulatory documents advise against making dosage adjustments, such as doubling the dose, without consulting a healthcare provider, as consistent dosing is important for the treatment plan.

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Q: How should I store Susten capsules?

According to official regulatory sources, Susten capsules should be stored in their original packaging, below 30 C, and protected from moisture and light. As with all medications, it is essential that the medicine is kept out of the reach and sight of children.

How to Store and Dispose of Susten

The storage and disposal of Susten (progesterone) must comply strictly with conditions defined in official regulatory labeling to ensure product stability and safety.

Storage Requirements

Susten must be kept at controlled room temperature, specifically between 20 C and 25 C (68 F and 77 F). The product must not be frozen and must be kept away from excessive heat and moisture. It is required to store the capsules in their original container and keep the container tightly closed and protected from light. A mandatory regulatory instruction is to keep the medicine out of the sight and reach of children.

Disposal Instructions

Do not dispose of unused or expired Susten via wastewater or household waste. Patients should consult a pharmacist or local waste disposal service for guidance on how to properly discard the medicine, following procedures that help protect the environment.