Geston

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Geston

Method of action: Progestogen

Treatment option: Miscarriage

Medically reviewed

Marina Burgos

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Geston

Property Description
Active Ingredient Allylestrenol
Form Tablet (Oral formulation)
Pharmacological Class Synthetic Progestogen
Common Purpose Supports uterine stability/pregnancy maintenance
Origin Synthetic (Steroidal derivative)

What is Geston and its Pharmacological Class?

Geston is a prescription-only hormonal drug whose active component is Allylestrenol, which officially classifies it as a Synthetic Progestogen and a Steroid Hormone Receptor Agonist. This medication is chemically modified from natural hormones, allowing it to function effectively as a substitute or supplement for the body's natural progesterone. Its role as a stabilizing agent in reproductive health is clinically recognized among hormonal therapies. Progestins, such as Allylestrenol, promote secretory changes in the endometrium, establishing conditions necessary for maintaining gestation. This medication is designed to support the physiological stability required during pregnancy, a typical use scenario for this class of drug.


Allylestrenol: The Composition, Form, and Origin

The preparation of Geston focuses exclusively on its active ingredient, Allylestrenol, defining it as a single-ingredient product designed for targeted hormonal support. Unlike naturally occurring progesterone, Allylestrenol is entirely synthetic, created in a laboratory as a Delta^4-estrane derivative to ensure stability for oral administration. This particular formulation is known for its reliable absorption profile when administered by mouth. The medicine is typically supplied as an oral formulation in the form of a tablet, which allows for consistent and systemic distribution. This structural stability is crucial because it ensures the compound remains active as it is absorbed and distributed throughout the body, targeting women of childbearing age.


What is the General Purpose of This Synthetic Progestin?

The general purpose of this synthetic progestin is to promote and sustain a state of hormonal balance within the uterus. Geston achieves this through its high progestational activity, which supports the necessary maintenance of endometrial integrity and promotes uterine calmness. By activating progesterone receptors, the drug works to reduce excessive muscle tightening or spontaneous contractions within the uterus. Its conceptual benefit is to reinforce the body's hormonal conditions required for supporting reproductive health.

Regulatory References

  1. NIH: Progestins
  2. MedlinePlus: Birth Control Pills

What side effects are possible with Geston?

Possible side effects and safety information

The safety profile for Geston (Allylestrenol), a synthetic progestogen, is based on official governmental regulatory documents which categorize potential effects by frequency and system. This structure ensures accurate communication of the medicine's documented risks and constraints.

Category Details (As documented in regulatory sources)
Common Adverse Reactions Nausea, vomiting, and headache are frequently documented in the Gastrointestinal and Nervous System Disorders categories.
Other Documented Reactions Further documented effects, for which a precise frequency is often Not Known, include fatigue, dizziness, bloating, breast tenderness, and skin reactions.
Serious Systemic Risks The official label documents the potential for serious Thromboembolic Events (e.g., deep vein thrombosis, pulmonary embolism) and Cholestatic Jaundice as high-level risks associated with steroid hormones.
Safety-Related Restrictions The medicine is contraindicated in cases of known hypersensitivity to any component, in individuals with confirmed or suspected hormone-dependent tumours, and in the presence of undiagnosed vaginal bleeding.
Population Considerations Extreme caution or contraindication is specified for patients with severe hepatic impairment due to the potential for liver enzyme changes and dysfunction.

Some adverse effects, such as gastrointestinal and neurological complaints, are noted to be more frequently observed at the beginning of treatment. The safety profile can also be impacted by co-administration with strong CYP enzyme inducers, which are cited as potentially altering Allylestrenol's metabolism.

The overall safety profile is structured by categorizing effects by system and frequency, clearly defining common non-serious complaints and the mandatory limitations on use related to pre-existing severe conditions.

Overdose and Emergency Response

Overdose and When to Seek Help

Official regulatory documents addressing acute overdose with Geston (Allylestrenol) provide specific instructions regarding required actions, rather than a comprehensive list of clinical symptoms. The documented overdose profile is based on the ingestion of multiple tablets at once.


Overdose Scope

Element Official Regulatory Statement
Documented overdose presentations None explicitly stated. Specific clinical signs or symptoms are not formally documented.
Dose-related or exposure-related factors Ingestion of "several tablet at once" is the exposure scenario addressed by the regulatory guidance.
Emergency-response statements Consult your doctor is the explicitly mandated action required following ingestion of multiple tablets.

Overdose Classifications (High-Level)

Element Official Regulatory Statement
Severity classification Low documented severity. Regulatory-aligned text indicates there is generally "no need for great concern."
Overdose-context constraints No specific antidote is known or documented in the regulatory overdose sections.

Resulting Overdose Structure

Official overdose statements:

  • The official prescribing information states that taking several tablets at once is generally of low documented concern.
  • The officially mandated action following ingestion of an acute overdose is to consult your doctor.
  • No specific antidote or detailed clinical manifestations are explicitly documented in the regulatory overdose text.

Connection to the overall overdose profile: Regulatory documents define the Allylestrenol overdose profile by stating that severe or life-threatening symptoms are not officially expected upon acute ingestion. The official guidance emphasizes that the essential emergency action is to immediately consult a doctor, which ensures the patient receives professional evaluation. This action is required because no specific antidote is documented in the label, making symptomatic and supportive management the necessary approach.

Therapeutic Uses of Geston

What Geston Treats: Main Uses and Benefits

Geston (Allylestrenol) is commonly used to help with conditions that may affect the stability and continuation of pregnancy. This progestogen is considered relevant for managing certain high-risk conditions associated with pregnancy loss.

Geston is used for managing conditions characterized by periods of heightened symptoms, specifically threatened miscarriage and a history of recurrent pregnancy loss. The medicine helps address symptom clusters like unexpected vaginal bleeding and lower abdominal pain associated with uterine instability. This supportive therapy supports patients during difficult episodes associated with a threat to pregnancy, assisting with maintaining a sense of stability when symptoms are more noticeable.

The medication is relevant for easing symptoms related to heightened physiological activity, specifically excessive uterine irritability. This contributes to improved comfort and is relevant for easing symptoms of increased muscular activity. This action is applied in clinical settings where temporary symptomatic assistance is needed, when supportive symptom management is appropriate. The medication is relevant in contexts involving heightened systemic burden, including the need for hormonal support in reproductive medicine.

Quick Fact: Support for Symptoms of Uterine Irritability

Eligibility and Restrictions for Use

The eligibility for using Geston (Allylestrenol) is strictly defined by regulatory authorities and is based on a patient's medical history, clinical status, and age.

Contraindicated Populations

Geston is absolutely contraindicated for use in several specific populations. This includes patients with a known history of Thrombophlebitis, Cerebral Apoplexy, or any Hormone-Dependent Carcinoma, such as breast or uterine cancer. Use is also prohibited in cases of Severe Hepatic Impairment, Undiagnosed Vaginal Bleeding, or a current Incomplete Abortion. The drug is not to be used as a diagnostic test for pregnancy.


Age and Life Stage Restrictions

Use is not recommended for individuals younger than 16 years old. Regarding reproductive status, the medication is permitted during pregnancy for its intended purpose but must be discontinued immediately after delivery as use is prohibited during lactation.


Conditional Use

Regulatory documents establish that Geston requires formal caution when administered to patients with specific pre-existing conditions, including Heart Disease, Renal Dysfunction, Seizures or Epilepsy, Migraine Headaches, and certain Breathing Diseases.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Geston (progesterone) is metabolized in the liver, primarily by the CYP3A4 enzyme system. The concurrent use of other medicines, herbal products, or substances that affect this enzyme can change the concentration of Geston in the body, potentially leading to a loss of therapeutic effect or an increase in side effects.

Key Interaction Categories

Interacting Product Category Potential Effect on Geston Clinical Note
Strong Enzyme Inducers (e.g., rifampicin, phenytoin, carbamazepine, phenobarbital) Reduced Geston plasma concentration Avoid co-administration due to risk of therapeutic failure (e.g., loss of contraceptive efficacy).
CYP3A4 Inhibitors (e.g., ritonavir, ketoconazole, clarithromycin, grapefruit juice) Increased Geston plasma concentration Use with caution; may increase the risk of side effects.
Herbal Products (e.g., St John’s wort) Reduced Geston plasma concentration Documented association with reduced contraceptive effect.

Other Relevant Interactions

Medicines or conditions that affect the gastrointestinal tract, such as severe vomiting or diarrhoea that results in incomplete absorption, may also reduce the amount of Geston entering the bloodstream. Additionally, Geston may interact with other hormone receptor modulators, such as ulipristal acetate, and should not be used immediately following its administration. Always inform a healthcare professional of all medicines and supplements being taken.

Mechanism of Action

How Geston Works

Geston is a synthetic progestogen that exerts its pharmacological effects by engaging distinct mechanistic domains to modulate reproductive physiology.


Nuclear Receptor-Mediated Signaling

Geston functions as an agonist of the nuclear progesterone receptor (nPR), a ligand-activated transcription factor primarily located in target tissues like the endometrium. Binding to nPR initiates or suppresses specific gene transcription, leading to endometrial secretory transformation and influencing the synthesis of proteins that regulate local tissue environment.


Neuroendocrine Pathway Modulation

The compound modifies the hypothalamic-pituitary-gonadal (HPG) axis via negative feedback exerted on the pituitary gland. This regulatory action suppresses the pulsatile release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which results in the suppression of follicular rupture.


Local Environment Adjustment

Additionally, Geston modulates molecular steps within the reproductive tract. It alters the properties of cervical mucus, causing it to become thicker and less penetrable, which results in decreased sperm motility. Concurrently, it reduces mitotic activity in the endometrium, promoting a state of reduced cellular proliferation.

Dosage and Administration Information

How Geston (Allylestrenol) Is Used

Geston is a prescription-only hormonal drug administered exclusively through the oral route as a mathbf5 mg tablet. Its administration is defined by specific dosage and duration protocols.

Standard Dosage and Frequency

Established dosing regimens are non-interchangeable and dependent on the clinical context. For threatened abortion, the typical daily regimen is mathbf15 mg, often administered as mathbf5 mg three times a day (TID). In cases of habitual recurrent pregnancy loss, the dose commonly ranges from mathbf5 mg to mathbf10 mg daily. More acute threatened conditions may follow protocols authorizing dosages up to mathbf40 mg daily.

The frequency pattern involves either once-daily use for maintenance or a divided-dose schedule for acute management. The medicine should be taken at approximately the same time each day to maintain consistent systemic levels, and it may be consumed with or without food.

Duration and Procedural Rules

Duration of use is not fixed but is tied to specific clinical endpoints. Administration is intended to continue until at least one month after the critical risk period has passed. Following the resolution of acute symptoms, the dosage often requires gradual dose reduction (tapering) before the medication is discontinued.

Key administration rules state that patients should not take a double dose to compensate for a missed one. Additionally, Geston is not recommended for use in children under the age of 16 years.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Geston


Evidence for Use in Recurrent Pregnancy Loss

Geston (Allylestrenol) was studied for women with a history of recurrent pregnancy loss (RPL), which is defined as two or more previous pregnancy losses. Research for this use primarily includes Randomized Controlled Trials (RCTs) and meta-analyses that review the findings from multiple trials. These studies research examined outcomes related to successful delivery, specifically the live birth rate, the rate of ongoing pregnancy past the first trimester, and the incidence of pregnancy loss before 24 weeks.

The findings describe patterns observed in the studies where Allylestrenol was associated with certain pregnancy outcomes when observed in the studies. However, the evidence is limited and varies in quality. There is also limited information for long-term outcomes beyond the initial pregnancy, and the data for certain groups remain insufficient. Research does not determine whether an individual will respond similarly to the group patterns observed.


Evidence for Use in Threatened Miscarriage

For women experiencing threatened miscarriage—a condition characterized by unexpected vaginal bleeding or lower abdominal pain in early pregnancy—Allylestrenol was evaluated in comparative clinical trials and observational studies. This research examined outcomes such as successful delivery rate, the miscarriage rate, and changes in clinical symptoms like bleeding and pain. This approach is relevant in trials assessing short-term or episodic symptom patterns.

The findings indicate patterns related to key clinical and delivery outcomes observed during these acute episodes. Evidence is still developing for this specific use across all women with threatened miscarriage symptoms. Some of the consistency was observed to vary, and the available evidence often involves comparisons to other progestogens rather than rigorous comparison to a placebo or non-treatment group in a large-scale, recent RCT. The results apply only to the populations studied.

ightarrow Evidence in Contexts Requiring Luteal Phase Support

Geston was also studied for its relevance in related research contexts, such as hormonal support during the luteal phase of assisted reproductive techniques (ART) like IVF. This evidence primarily consists of retrospective observational studies. Research examined outcomes related to clinical pregnancy rate and live birth rate in women undergoing these procedures. The follow-up durations were limited in these studies, typically extending only until the end of the first trimester.

Key Studies & References Progestins: MedlinePlus Drug Information (General Class Description)

Frequently Asked Questions (FAQ)

Common questions about Geston (FAQ)


Q: What are the approved uses of Geston by regulatory bodies like the FDA or EMA?

Regulatory documents from various international agencies describe Geston's primary purpose as supporting pregnancy. This includes preventing threatened miscarriage and recurrent miscarriage, and managing preterm labor in some contexts. The medicine is described as a progestogen used to support conditions requiring uterine stability.


Q: What kind of research or clinical evidence supports the use of Geston?

Clinical research, including Randomized Controlled Trials (RCTs) and meta-analyses, has been conducted to observe the drug's use in women with recurrent pregnancy loss and threatened miscarriage. These studies examine outcomes such as live birth rate and preterm birth rate. The findings are referenced in official prescribing guidelines.


Q: Are there different strengths or formulations of Geston available?

Official product information describes Geston as available in an oral tablet form, typically in a 5 mg strength. It is officially not available in injectable or extended-release formulations. The medicine is prepared as an oral tablet.


Q: Is Geston generally considered a long-term or short-term medication?

The duration of Geston use is determined by the healthcare provider and is tied to specific clinical endpoints and pregnancy risk factors. For its intended uses, official documents describe a defined therapeutic duration, often continuing through the first trimester or until after the critical risk period has passed.


Q: Is Geston used to treat chronic conditions or only acute episodes?

Official documentation indicates that Geston is used for both acute episodes and recurrent conditions. Acute uses involve conditions like threatened abortion, while recurrent uses are described for conditions like habitual abortion caused by luteal phase defects.


Q: How does Geston compare to other medications in the same class of drugs?

Geston (Allylestrenol) is described as a pure progestogen in official literature. It is characterized as being devoid of androgenic, estrogenic, and glucocorticoid activity. This is a pharmacological distinction noted when compared to some other synthetic progestins.


Q: Does Geston interact with alcohol?

Official safety advice suggests caution regarding the use of Geston with alcohol. Regulatory information indicates that there is not enough scientific data available to define the precise interaction, so it is generally advised to approach alcohol use with caution.


Q: Is it known if Geston interacts with common dietary supplements like vitamins or herbal products?

Official documents explicitly note that certain herbal products, such as St. John's wort, are known to interact with the liver enzymes that metabolize Geston, which can potentially lower its levels. Specific interactions with general vitamins or common dietary minerals are not explicitly detailed in the official label.


Q: Is Geston associated with any potential long-term side effects?

Clinical research for Geston's primary use in pregnancy maintenance has typically focused on outcomes up to or shortly after delivery. Because of this, the available research has limited information on effects or outcomes following very long-term use of the medication.


Q: What information is available about Geston's use in older adults?

As Geston is a hormone drug indicated for reproductive health, official documents do not typically specify information regarding its use, safety, or dosage adjustments for individuals in older age groups (e.g., above 65 years).


Q: Does Geston affect the ability to drive or operate machinery?

Official safety information states that Geston may cause dizziness or drowsiness as documented side effects. For this reason, official guidance suggests caution regarding activities such as driving or operating machinery.


Q: What is the risk of dependency or withdrawal symptoms described for Geston?

Regulatory instructions advise that Geston often requires a gradual dose reduction (tapering) process before the medication is entirely discontinued. This procedural rule is specified in official instructions for safe discontinuation.


Q: Are there any restrictions on activities or lifestyle changes while taking Geston?

Official restrictions on activities primarily include the need for caution when driving or operating machinery due to potential dizziness or drowsiness. Safety advice also suggests caution regarding alcohol consumption during treatment.


Q: Is Geston used for a purpose that involves hormone regulation?

Yes, Geston is officially classified as a Synthetic Progestogen, meaning it is chemically related to the body's natural progesterone hormone. Its purpose is described as promoting conditions of hormonal support within the uterus.


Q: Why is the same medicine sometimes known by two different names (generic vs. brand)?

Medicines are generally identified by two types of names: the brand name (like Geston) is the specific commercial name given by the manufacturer. The generic name (Allylestrenol) refers to the official active ingredient and typically remains consistent regardless of the manufacturer.


Q: Is Geston known to cause allergic reactions, and what are the signs to look for?

Official labeling notes that Geston is contraindicated if a patient has a known hypersensitivity to any of its components. Safety information lists descriptions of allergic reactions to be aware of, such as skin rash, swelling, or breathing difficulty.


Q: Why do some people report feeling worse before feeling better on Geston?

Regulatory documents address the timing of certain non-serious side effects. They specifically note that complaints related to the gastrointestinal and neurological systems (like nausea or headache) are more frequently observed at the beginning of treatment with Geston.


Q: Is Geston an anti-inflammatory medicine?

No, Geston's active component, Allylestrenol, is officially classified as a Synthetic Progestogen and a Steroid Hormone Receptor Agonist. It is not classified as an anti-inflammatory medicine, but rather as a hormonal therapy.


Q: What are the key safety statements listed in the Patient Information Leaflet for Geston?

The key safety statements define mandatory limitations on the drug's use. These statements indicate that the medicine is contraindicated in cases of known hypersensitivity, confirmed or suspected hormone-dependent tumours, and in the presence of undiagnosed vaginal bleeding.

How should Geston be stored and disposed of?

How to Store and Dispose of Geston (Allylestrenol Tablets)

Storage Conditions

Geston tablets must be stored according to regulatory requirements to preserve the drug's quality and stability.

Condition Requirement
Temperature Store below 30°C (86°F).
Protection Keep in a dry place and protect from moisture and light.
Container Must remain in the original package until the time of use.

Child Safety and Disposal

All medicine must be kept out of the sight and reach of children to prevent accidental ingestion.

Unused or expired Geston tablets must not be disposed of in household trash or poured down a sink or toilet. Disposal should be managed through an official pharmacy take-back scheme or local waste collection program that handles unused medicines, as dictated by environmental and public health regulations.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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