Megestat

Quick links to important sections

Megestat

Method of action: Endocrine Therapy

Treatment option: Anorexia, Cachexia, Cancer, Breast Cancer

Medically reviewed

Laura Arias

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 Megestat

Defining Megestat: Classification and Origin

Property Description
Active ingredient Megestrol acetate
Form Tablet and oral suspension
Pharmacological class Progestin, Hormonal Antineoplastic
General purpose Hormonal modulation and appetite influence
Origin Synthetic derivative
Status Prescription-only (Rx)

The medication whose active component is Megestrol acetate is a potent synthetic progestogen derivative that is available strictly by prescription (Rx). This substance belongs to the progestin pharmacological class, chemically derived from the naturally occurring steroid hormone progesterone. It is clinically recognized for its ability to modulate specific hormonal pathways. The medicine acts by mimicking the body’s progesterone.

Unlike the natural hormone, the synthetic derivation optimizes its affinity for specific hormone receptors, which is a key factor in its therapeutic profile. The benefit of this targeted activity is its ability to modulate powerful hormonal pathways in the body and influence systemic processes related to cell proliferation, making it useful in contexts such as palliative care support.

Forms, Composition, and General Function

Megestrol acetate is supplied as a monocomponent medicine intended for oral administration. It is commonly manufactured in two primary dosage forms: a solid tablet and a liquid oral suspension, offering flexibility in patient administration. As a progestin, its fundamental function centers on activating progesterone receptors, which provides its primary hormonal mechanism. A crucial feature that differentiates it from some other progestins is its clinically studied interaction with glucocorticoid receptors. This medication has the capacity to stimulate the body's desire for food.

This dual characteristic allows the medicine to serve the general purpose of providing hormonal treatment and, separately, influencing the body's metabolic state to promote appetite, a distinguishing factor.

Regulatory References

  1. NCI Drug Dictionary: Megestrol acetate

What side effects are possible with Megestat?

Possible Side Effects and Safety Information

This section summarizes the adverse reactions and safety restrictions for Megestat (megestrol acetate) based strictly on official government regulatory documentation.

Serious and Clinically Significant Safety Risks

Regulatory agencies highlight the potential for thromboembolic disease, including deep vein thrombosis and pulmonary embolism, which may be fatal. Chronic use of this medicine is associated with risks of adrenal insufficiency and overt Cushing's syndrome due to its potential for glucocorticoid effects. Patients receiving or being withdrawn from chronic therapy require surveillance for symptoms suggestive of hypoadrenalism.

Frequency-Classified Adverse Reactions

In clinical trials, the following were documented as the most common adverse events, occurring in over 5% of patients:

  • Nausea
  • Diarrhea
  • Weight gain
  • Impotence
  • Rash
  • Hypertension
  • Asthenia (lack of energy/weakness)

Safety Restrictions and Contraindications

The medicine is contraindicated during known or suspected pregnancy due to the potential for fetal harm. Nursing mothers are advised to discontinue nursing due to potential adverse effects on the newborn. Caution is advised when prescribing to patients with a history of thromboembolic disease. The use of this drug can also lead to the new onset or exacerbation of diabetes mellitus.

Overdose and Emergency Response

Overdose and When to Seek Help

The official regulatory documents define the overdose profile for Megestrol acetate, noting a high tolerance level in clinical studies. No acute toxicological effects were reported when doses as high as 1600 mg/day were administered over six months or more. However, specific clinical signs have been documented in postmarketing reports.

Documented Manifestations Regulator-Mandated Actions
Gastrointestinal: Nausea, diarrhea, abdominal pain. Seek immediate medical attention if severe symptoms such as chest pain or shortness of breath occur.
Systemic: Shortness of breath, cough, unsteady gait, listlessness, chest pain. Treatment must be symptomatic and supportive.

There is no specific antidote known for Megestrol acetate overdose documented in official labeling. The regulatory profile indicates that due to the low solubility of the drug, procedures like haemodialysis are postulated to be ineffective and are not recommended as a treatment measure. Management in all cases requires professional clinical evaluation.

Therapeutic Uses of Megestat

What Megestat Treats: Main Uses and Benefits

Megestrol acetate is commonly used across two primary therapeutic domains. This includes situations involving symptomatic discomfort related to wasting syndrome and palliative hormonal treatment for advanced, hormonally-sensitive cancers.


Supporting Appetite and Managing Severe Weight Loss

This therapeutic domain addresses the symptom clusters of anorexia and cachexia (wasting syndrome), which are conditions involving significant weight loss often seen in patients with advanced cancer or acquired immunodeficiency syndrome (AIDS). The primary benefit is to help address severe appetite loss, which may assist in supporting nutritional intake and general comfort during symptomatic periods. This supports general well-being during symptomatic phases.


Palliative Hormonal Therapy for Advanced Cancers

Megestat is applied in addressing specific advanced, recurrent, or metastatic carcinoma of the breast and endometrium when the disease is relevant to hormonal modulation. This use may be part of symptomatic management, which contributes to easing the overall symptom load and supports the patient during difficult episodes by easing distress in challenging symptomatic phases.


Quick Fact: Relief for Wasting Symptoms
Primary Symptom Targeted Severe, pathology-driven loss of appetite (anorexia).
Palliative Benefit Supports the patient by assisting with nutritional stability and comfort.

Eligibility and Restrictions for Use

Megestrol acetate eligibility is determined by strict criteria outlined in regulatory documents, defining who is absolutely prohibited from use and who requires conditional caution. Adults are the established population for the labeled uses.

Populations for whom use is Contraindicated

Category Regulatory Status
Pregnancy Contraindicated (Known or suspected)
Hypersensitivity Contraindicated (History of allergy to megestrol acetate or components)

Age-Related and Condition-Based Eligibility

Population Group Eligibility Status
Pediatric Use Safety and effectiveness have not been established; not recommended for use in children.
Lactation/Breastfeeding Not recommended; nursing should be discontinued if treatment is required.
Thromboembolic Disease Use with caution (History of blood clots).
Diabetes Mellitus Use with caution (Risk of worsening or new onset of diabetes).
Impaired Renal Function Use with caution (Drug is substantially excreted by the kidney).

Eligibility is also restricted to patients whose treatable causes of weight loss (e.g., systemic infections, endocrine disease) have been sought and addressed prior to starting therapy.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official government regulatory information establishes specific constraints regarding the co-administration of Megestat (megestrol acetate) with certain other medicines. The documented interactions primarily involve drugs whose effects or safety profiles may be significantly altered.

Clinically Significant Interactions

The following table summarizes documented drug interactions that require specific monitoring or management according to official labeling:

Interacting Medicine Class Specific Interacting Medicine Official Constraint/Management Guideline
Antivirals (Protease Inhibitors) Indinavir Coadministration results in a significant decrease in Indinavir exposure. Consider a higher dose of Indinavir when used together.
Anticoagulants (Coumarin Derivatives) Warfarin Associated with an increase in International Normalized Ratio (INR). Frequent monitoring of INR should be considered for patients taking both drugs.

Interaction Profile Structure

The overall regulatory profile is defined by pharmacokinetic and pharmacodynamic constraints. The interaction with Indinavir is categorized as a pharmacokinetic effect that requires dose adjustment consideration for the co-administered drug. The interaction with Warfarin is categorized as requiring close monitoring (e.g., of INR) to manage a potential pharmacodynamic change. These specific requirements ensure appropriate risk mitigation when these medicines are prescribed concurrently.

Mechanism of Action

How Megestat Works

Megestrol acetate, a synthetic progestin, exerts its effects primarily by binding to and activating the intracellular progesterone receptor (PR), which functions as a ligand-activated transcription factor. This binding initiates a conformational change in the PR, allowing the activated receptor complex to translocate to the cell nucleus. Once nuclear, the complex interacts with specific DNA sequences, known as progesterone response elements (PREs), to regulate target gene transcription.

This transcriptional modulation directly influences activity within the hypothalamic-pituitary-adrenal (HPA) axis. A critical downstream cascade involves the inhibition of gene transcription for pro-inflammatory cytokines, specifically Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-6 (IL-6). The suppression of these inflammatory mediators alters neurohormonal feedback loops in the hypothalamus, which influences the balance between orexigenic and anorexigenic signaling pathways.

At a cellular level, megestrol acetate influences substrate utilization by modifying glucose and lipid metabolism pathways, and its progestational action modulates the activity of osteoblast and osteoclast cells, thereby affecting catabolic processes within skeletal tissue.

Dosage and Administration Information

How Megestrol Acetate is Used

Megestrol acetate is an oral medication administered either as a tablet or a liquid oral suspension. The frequency and exact dose range are dictated by the specific clinical context.

Administration and Dosing Principles

The medicine is used in specific daily amounts that vary based on the intended regimen. For advanced breast carcinoma, the standard adult regimen is a total of 160 mg per day, typically taken as 40 mg four times daily (QID) in divided doses. For advanced endometrial carcinoma, the dose range may span from 40 mg to 320 mg per day, also taken in divided doses.

When used as an oral suspension for appetite support, the common dose is 800 mg once daily (QD), using the standard 40 mg/mL concentration. Importantly, the high-concentration 125 mg/mL suspension is not interchangeable on a milligram-for-milligram basis with the 40 mg/mL concentration. Due to differences in absorption, the high-concentration product is taken after a meal.

Procedural Requirements and Duration

Prior to administration, the oral suspension container must be shaken well to ensure proper dosage. In terms of duration, continuous treatment for at least two months is considered the standard period before evaluating the procedural effectiveness of the medicine for cancer indications. For older adults, dosing may be initiated at the low end of the range, reflecting the need for caution in this population.

Recent Clinical Evidence

Research evidence / Overview of Studies for Megestat

The information below describes the research structure and the types of findings reported in clinical studies on megestrol acetate, using neutral language and highlighting what remains uncertain in the evidence landscape.


Evidence for Managing Appetite Loss and Wasting Syndrome

Research in this area primarily consists of short-term, randomized, double-blind trials where patients were compared to a group receiving a placebo (an inactive substance). Research explored whether megestrol acetate was associated with outcomes related to appetite and weight measurements in settings linked to diagnoses like Advanced Cancer and Acquired Immunodeficiency Syndrome (AIDS).

Findings from these trials describe patterns observed in the studies where patients receiving megestrol acetate reported different scores on appetite scales compared to the placebo groups over the study period. Additionally, research highlights measured changes during the study period, reporting patterns in body weight measurements in the observed populations. Studies monitoring body composition reported that the measured weight was primarily associated with changes in fat mass. Findings related to quality of life measures were described as limited or inconsistent.


Evidence for Palliative Hormonal Therapy

Studies explored this use mainly through Phase II and Phase III clinical trials, which monitored patient outcomes related to cancer symptoms and tumor markers. Research examined women, primarily postmenopausal, with hormone receptor-positive tumors for advanced, recurrent, or metastatic Carcinoma of the Breast and Carcinoma of the Endometrium.

Trials reported that research monitored and captured specific outcomes, such as objective response rates and clinical benefit rates, in a portion of the populations studied. Studies describe its use as a later-line therapy where disease stabilization was noted. Research provides insight into short-term changes and contributes to the broader evidence landscape for palliative care options.


Study Focus on Long-Term Outcomes and Follow-up

The majority of pivotal clinical trials concerning the use of megestrol acetate to influence appetite had limited follow-up duration, often lasting 8 to 12 weeks. This means that the evidence base provides limited information for long-term outcomes related to sustained appetite or weight maintenance beyond the primary observation intervals.

In the cancer settings, trials for hormonal therapy often involve longer follow-up to monitor specific outcomes, such as the time elapsed before disease progression, over months or years. However, even these studies focus on describing how symptoms evolved in the observed populations and long-term effects are not fully established regarding sustained functional status or survival.

Frequently Asked Questions (FAQ)

Common questions about Megestat (FAQ)

Q: Is it normal to feel mood changes or sleep disturbances when using Megestat?

A: Official product information, based on reported events in studies, indicates that some patients have experienced sleep disturbances, specifically insomnia (trouble sleeping). Additionally, psychiatric-related events like depression and abnormal thinking are listed among the reported adverse effects. Concerns about mood or sleep should be discussed with a healthcare provider.


Q: What happens if a dose of Megestat is missed?

A: Patient information derived from regulatory guidelines advises that if a dose is missed, the general patient information advises taking it as soon as it is remembered. However, if it is almost time for the next scheduled dose, the advice is to skip the missed dose and continue with the regular schedule. It is advised that a double dose not be taken to make up for the missed dose.


Q: What are the signs of a serious side effect from Megestat that need immediate attention?

A: Regulatory documents highlight the potential for serious conditions, such as the new onset or worsening of diabetes and problems with the adrenal glands. Official patient materials describe signs such as extreme dizziness, severe or persistent changes in bowel habits, or sudden changes in vision as requiring guidance from a healthcare professional immediately.


Q: Can Megestat cause fluid retention or swelling?

A: Yes, edema, which is the term for fluid retention or swelling, has been reported as an adverse reaction in clinical trials. This finding is included in the official product information.


Q: Can Megestat make you feel dizzy or affect your ability to drive?

A: Dizziness is a reported adverse reaction associated with this medication. Due to the reported occurrence of dizziness, official guidance advises caution regarding activities that require alertness, such as driving or operating machinery.


Q: What should I tell my dentist or surgeon before a procedure if I'm taking Megestat?

A: Regulatory documents indicate that informing surgical staff or your dentist of Megestat use is necessary. Chronic use of the medicine can affect the adrenal glands' ability to respond to stress. Patients undergoing major physiological stress, such as surgery or serious illness, may require monitoring and specific care.


Q: Does Megestat cause hair loss or changes in hair growth?

A: Official product information notes that alopecia, which is the medical term for hair loss, has been reported as an adverse event in people taking this medication.


Q: Are there any specific foods or drinks that should be avoided when taking this medication?

A: The official administration instructions specifically advise taking the high-concentration oral suspension (the 125 mg/mL formulation) after a meal due to absorption characteristics. No general food or drink avoidance is typically listed for the other forms.


Q: Is the liquid suspension form of Megestat equivalent to the tablet form?

A: Official documentation states that the high-concentration oral suspension (125 mg/mL) is not interchangeable on a milligram-for-milligram basis with the standard concentration suspension (40 mg/mL) or other forms. Equivalence between the liquid and tablet forms is not generally assumed, and specific concentrations of the suspension are known to be non-interchangeable.


Q: Will Megestat still work if I take it before eating, or does timing matter?

A: Timing is specified for one formulation. The administration instructions for the high-concentration oral suspension (125 mg/mL) specifically advise that it should be taken after a meal. This timing instruction ensures proper absorption of the medicine.


Q: Can people with kidney or liver problems take Megestat?

A: Regulatory information advises caution when prescribing Megestat to patients with impaired renal function (kidney problems). This is because the kidneys are the main way the drug is removed from the body. There is not sufficient information in core official documents to provide a definitive statement on liver problems.


Q: Does the use of Megestat require special monitoring or blood tests?

A: Yes, monitoring is required in specific situations. For example, close surveillance is necessary to check for signs of adrenal insufficiency in patients on chronic therapy. If the drug is taken alongside the anticoagulant Warfarin, official documents state that INR blood tests must be frequently monitored.


Q: Can patients who are lactose intolerant or have allergies take Megestat?

A: The tablet form of the medicine lists anhydrous lactose as an inactive ingredient. Furthermore, the medicine is contraindicated (should not be used) for anyone with a known history of hypersensitivity or allergy to megestrol acetate or any of the product's components.


Q: Is it okay to stop taking Megestat suddenly?

A: Official documentation implies that stopping treatment suddenly is a regulated process. Patients being withdrawn from chronic therapy require close medical surveillance. The surveillance is required to monitor for symptoms related to hypoadrenalism (adrenal gland problems).


Q: Does Megestat help improve energy levels, or just appetite?

A: The medicine is primarily studied for its effect on appetite and weight. Asthenia (lack of energy or weakness) is listed as a common adverse event. Furthermore, research findings on general quality of life measures, which would include energy, have been described as limited or inconsistent.

How should Megestat be stored and disposed of?

How to Store and Dispose of Megestrol Acetate (Megestat)

Megestrol acetate, including the oral suspension and tablets, must be stored at Controlled Room Temperature, typically 20 C to 25 C (68 F to 77 F). The medication must be protected from freezing, excessive heat (over 40 C), light, and moisture. Store the medication in its original container, and keep the oral suspension bottle tightly closed.

Child Safety and Disposal

All forms of megestrol acetate must be kept out of the reach of children. Unused or expired medicine should be disposed of according to local and national regulations, preferably through a drug take-back program. If a take-back option is unavailable, the medication must be prepared for household trash disposal by mixing it with an undesirable substance, such as dirt or used coffee grounds, before sealing and discarding.

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

Available in countries:

Equivalent of Megestat found in:

A-Z Index: