Megestol

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Megestol

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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 Megestol

Property Description
Active Ingredient Megestrol Acetate (INN)
Form Tablet, Oral Suspension
Pharmacological Class Progestogen (Progestin)
General Purpose Hormone modulation and appetite stimulation
Origin Synthetic derivative of progesterone

Megestrol Acetate: Defining the Medicine and Its Origin

Megestol is a prescription medication containing the active chemical substance Megestrol Acetate, which is fundamentally used for its hormonal effects and ability to stimulate appetite. The substance is classified as a synthetic steroid ester derived from the naturally occurring human hormone progesterone.

The drug's origin as a modified derivative of a natural hormone is significant, as this alteration makes it potent and effective when taken by mouth (orally administered). The availability of Megestol in both tablets and a liquid oral suspension offers flexibility in administration. Within the hormonal agents group, it is recognized for its role as an anti-androgen and progestin agent. This classification confirms the medicine works by influencing the body's natural hormone systems.


What Type of Agent is Megestol? Classification and Composition

Megestrol Acetate is classified primarily as a progestogen (or progestin), a pharmacological class of agents that bind to and activate progesterone receptors. As a single-ingredient product, it is composed of the active Megestrol Acetate combined with either solid excipients in the tablets or an aqueous suspension vehicle in the liquid form.

The main pharmacological action of Megestrol Acetate is its strong progestational activity. This action explains why the medicine is clinically recognized for its ability to affect conditions where managing the hormonal environment is necessary. Due to its structural design, this agent provides a reliable means of hormonal influence when absorbed through the digestive system.

What side effects are possible with Megestol?

Possible Side Effects and Safety Information

Official regulatory documents classify the adverse reactions associated with Megestrol Acetate based on the body systems affected and their frequency of occurrence. The safety profile is heavily influenced by the drug's hormonal properties, particularly its effects on metabolic and vascular systems.

Frequency-Classified Adverse Reactions

The most frequent adverse reactions are classified as Very Common (affecting 1 in 10 individuals or more) in regulatory labeling. These effects typically include weight increased, adrenal insufficiency, Cushing’s syndrome, hypertension, constipation, and disturbances in glucose tolerance and hyperglycemia.

Reactions classified as Common (affecting 1 to 10 in 100 individuals) involve areas like the gastrointestinal tract (e.g., nausea, vomiting, diarrhea), nervous system (e.g., confusion, lethargy), and reproductive system (e.g., erectile dysfunction, menrorrhagia).

Serious Safety Concerns and Restrictions

Regulatory authorities document the potential for serious adverse reactions, particularly thromboembolic phenomena, including the risk of Deep Vein Thrombosis (DVT) and Pulmonary Embolism. Adrenal insufficiency and Cushing’s syndrome are also highlighted risks, often associated with chronic use and observed during treatment or upon withdrawal.

Safety Restrictions define specific limitations on use. The medication is generally contraindicated in known or suspected pregnancy due to the risk of fetal harm. Caution is also advised for use in specific groups, such as older adults who may have decreased renal function, and individuals with a history of thromboembolic disease or pre-existing diabetes mellitus.

Overdose and Emergency Response

Overdose and When to Seek Help

Official regulatory information describes overdose with megestrol acetate as primarily resulting in a limited range of reported symptoms. These symptoms are documented based on post-marketing experience and not from specific toxicity studies. The symptoms reported in overdose situations include gastrointestinal effects such as diarrhea, nausea, and abdominal pain, along with general systemic signs like shortness of breath, cough, chest pain, and unsteady gait (listlessness).

Clinical Management and Emergency Action

It is officially stated that no specific antidote is available for megestrol acetate overdose. Therefore, clinical management of a suspected overdose must focus entirely on providing appropriate supportive measures for the patient.

Studies involving dosages as high as 1200 mg/day of the oral suspension have been noted to result in no serious unexpected side effects. However, due to the potential severity of symptoms affecting consciousness or vital functions, any suspected overdose requires immediate attention.

When to Call for Emergency Help

Immediate emergency medical help (e.g., calling emergency services) should be sought if an individual who has taken too much megestrol acetate collapses, has a seizure, experiences severe trouble breathing, or cannot be awakened.

Therapeutic Uses of Megestol

What Megestrol Treats: Main Uses and Benefits

Megestrol is generally used to provide supportive therapeutic benefit in two distinct clinical areas: managing significant body wasting and addressing symptoms related to hormone-sensitive cancers. Its use is relevant for easing certain distressing symptoms and contributing to improved day-to-day comfort. This medication is recognized as relevant in clinical settings marked by heightened systemic burden, specifically where nutritional and hormonal support are appropriate.

Combatting Severe Wasting Syndrome and Anorexia

This medication is applied in situations involving profound and involuntary weight loss (cachexia) and severe, persistent loss of appetite (anorexia) often associated with chronic diseases like advanced cancer or AIDS/HIV. It is used for managing these debilitating symptom patterns, as it generally assists with increasing food intake and may support body mass gain.

Palliative Hormone Modulation for Advanced Malignancies

Megestrol is also applied in addressing symptoms related to the therapeutic domain of advanced, hormone-sensitive malignancies, specifically certain types of advanced breast cancer and endometrial cancer that are recurrent or inoperable. It may be part of symptomatic management in these conditions, contributing to improved comfort and supportive relief in a palliative context.

The medication is applied in addressing symptoms related to conditions such as severe appetite loss, involuntary weight loss, advanced breast cancer, and recurrent endometrial cancer.

Quick Fact: Symptomatic Support for Severe Appetite Loss Megestrol is considered relevant for easing symptoms related to severe nutritional impairment and is used to help patients cope more steadily with chronic, debilitating conditions.

Regulatory References

  1. NIH MedlinePlus overview

Eligibility and Restrictions for Use

Who Can and Cannot Use Megestol?

Eligibility for Megestrol Acetate is strictly defined by regulatory authorities and is generally limited to adult patients with advanced carcinoma of the breast or endometrium, or those experiencing anorexia and significant weight loss associated with AIDS. Use is contraindicated in several specific populations.

Contraindications and Prohibited Use

Official labeling strictly prohibits use in patients with a history of hypersensitivity to the drug or any of its components. Megestrol Acetate is also contraindicated in women with known or suspected pregnancy, and it must not be used as a diagnostic test for pregnancy. Nursing mothers are advised to discontinue breastfeeding if treatment is required.

Populations Requiring Caution or Restriction

Use is not established and not recommended in pediatric patients. Caution is required when prescribing to older adults due to the increased frequency of decreased organ function, particularly in the liver and kidneys. Patients with impaired renal or hepatic function, a history of thromboembolic disease (blood clots), or pre-existing diabetes mellitus must also be managed with caution. Furthermore, use for weight loss is restricted until other treatable causes of the weight loss have been addressed.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory documentation details specific pharmacokinetic and pharmacodynamic interactions for Megestrol Acetate. The combination of Megestrol Acetate with certain medicines can lead to altered drug exposure or changes in physiological status.


Documented Interaction Patterns

Substance / Class Interaction Type Official Interaction Outcome
Indinavir (HIV Protease Inhibitor) Pharmacokinetic (PK) Co-administration results in a significant decrease in Indinavir exposure (decreased plasma levels).
Warfarin (Anticoagulant) Pharmacodynamic (PD) May cause an increase in International Normalized Ratio (INR), reflecting altered coagulation status.
Insulin / Oral Antidiabetic Agents Pharmacodynamic (PD) Associated with the exacerbation of pre-existing diabetes mellitus and an increase in insulin requirements.

Clearance and Restrictions

Formal studies have confirmed no significant alteration in the exposure of either Zidovudine or Rifabutin when co-administered. Due to the medicine’s substantial clearance by the kidney, official labeling notes that the risk of toxic reactions may be greater in patients with impaired renal function or in the elderly. The medicine is formally contraindicated in cases of hypersensitivity to the active substance or its components. Regulatory authorities state that the effect of food on the bioavailability of the Megestrol Acetate oral suspension has not been evaluated.

Mechanism of Action

Megestrol is a synthetic progestin that functions primarily as an agonist of the progesterone receptor (PR), a nuclear hormone receptor. The drug binds to the PR, causing the resultant ligand-receptor complex to translocate into the nucleus. Within the nucleus, the complex interacts with specific Hormone Response Elements (HREs) on the DNA, which modulates the transcription of target genes, altering the synthesis of various cellular proteins.

At the systemic level, megestrol's PR agonism exerts an antigonadotropic effect by suppressing the hypothalamic-pituitary-gonadal (HPG) axis. This occurs via a negative feedback mechanism on the pituitary gland, inhibiting the release of luteinizing hormone (LH). The resulting decrease in LH consequently suppresses ovarian estrogen synthesis and release.

Separately, megestrol also possesses glucocorticoid agonist activity, binding to and activating the glucocorticoid receptor (GR). This interaction is implicated in the modulation of the central neuroendocrine regulation of energy balance and metabolic pathways, including the antagonism of certain catabolic cytokines and the alteration of neuropeptide levels in the hypothalamus.

Dosage and Administration Information

How to Use Megestrol Acetate: Official Administration Guidelines

Megestrol Acetate is administered solely through the oral route, available in both tablet and liquid oral suspension forms. The specific dosage and frequency patterns depend on the condition being addressed.

Official Dosing and Frequency Patterns

Condition Standard Daily Dose Range Frequency Pattern
Advanced Breast Cancer 160 mg 40 mg four times daily (QID)
Advanced Endometrial Cancer 160 mg to 320 mg Divided doses (e.g., four times daily)
Cachexia/Anorexia (AIDS-Related) 625 mg to 800 mg Once daily

Administration Requirements and Duration

Megestrol Acetate tablets may be taken without regard to meals. When the liquid oral suspension is used, the container must be shaken well before the required dose is measured using a calibrated device.

It is established that a minimum of two months of continuous administration is considered an adequate duration to determine the full therapeutic effect in hormone-sensitive conditions. Dose selection for older adults is approached with caution, often starting at the lower end of the established dosing range. Furthermore, for females of reproductive potential, a negative pregnancy test is confirmed prior to initiating treatment.

Recent Clinical Evidence

Research Evidence: Overview of Studies for Megestrol Acetate

Megestrol Acetate has been studied in clinical research to examine its evaluation in two distinct clinical contexts: for the study of severe appetite loss and weight wasting, and as a hormonal agent for specific advanced cancers. The primary evidence base for both uses relies on Randomized Controlled Trials (RCTs) and scientific reviews that combine data from these trials.


Evidence for Use in Severe Appetite Loss and Weight Wasting

The most significant research body for Megestrol Acetate was studied for its use in severe, involuntary weight loss and persistent loss of appetite (anorexia-cachexia syndrome), conditions often associated with advanced chronic diseases, such as certain cancers and AIDS/HIV infection.

Research exploring how symptoms change over time has relied heavily on short-term RCTs that typically observed patient responses over intervals of 8 to 12 weeks. These studies monitored outcomes related to systemic or functional imbalance, specifically measuring changes in total body weight, patient-reported metrics of appetite change, and measurements of caloric intake. Studies reported that individuals in the research groups were associated with patterns of change in appetite and changes in weight.

It is not yet clear whether other outcomes are consistent. Evidence remains limited and heterogeneous regarding whether the medicine was associated with consistent changes in overall Quality of Life as assessed by functional scales. Furthermore, since follow-up durations were limited, the long-term effects of the medicine on weight and appetite remain not fully established.


Evidence for Use in Hormone-Sensitive Cancers

Megestrol Acetate was evaluated in clinical research for its role in conditions marked by functional limitations related to advanced, hormone-sensitive malignancies, specifically advanced breast cancer and for managing symptoms related to certain types of endometrial cancer that are recurrent or inoperable.

Studies explored the medicine through Phase II and Phase III RCTs to understand patterns of change. The research examined outcomes such as the objective change in tumor size, time until disease progression, and overall survival duration. Findings describe patterns observed in the studies, where trials reported that certain patient groups experienced observed changes in tumor size. For example, research describes patterns in patients with endometrial cancer where objective change in tumor size was observed in a fraction of the population, often linked to lower-grade tumors.

What remains uncertain is the full context of these findings. Comparative evidence is lacking against some newer hormonal treatments. Long-term studies, tracking outcomes for up to 8 years, provided context about dose comparisons, indicating that dose escalation did not translate to a measurable advantage in change rate.

Frequently Asked Questions (FAQ)

Common questions about Megestol (FAQ)


Q: How quickly does Megestol start to have an effect?

A: Official documents report that the medicine's concentration in the blood typically peaks between one and three hours after a dose. However, for conditions related to hormone modulation, regulatory guidelines specify that a minimum of two months of continuous administration is necessary to determine the full therapeutic effect.

Q: What are the important differences between Megestol and progesterone?

A: Megestrol Acetate is a synthetic (man-made) substance derived from the natural hormone progesterone. According to official product information, this modified structure possesses greater reported progestational activity compared to progesterone.

Q: Is Megestol known to cause mood changes or depression?

A: Official adverse reaction reports indicate that the medicine can cause nervous system effects. These are classified as common and include feeling confused or lethargic (tired/sluggish).

Q: What is the longest period of time people typically use Megestol?

A: The official prescribing information requires a minimum of two months of continuous use to assess the effect in hormone-sensitive conditions. For context, clinical research has provided data from long-term studies that tracked some patient outcomes for up to eight years.

Q: Can men use Megestol for any conditions?

A: Yes, official labeling indicates the drug is applicable to both male and female patients. Specifically, it is used for treating anorexia (appetite loss), cachexia, or significant weight loss associated with advanced illness like AIDS.

Q: Why is it important to know about adrenal suppression when using Megestol?

A: It is important because Megestol affects the body's glucocorticoid receptor, which is involved in stress response. Official documents warn that failure to recognize potential suppression of the adrenal system (known as the hypothalamic-pituitary-adrenal axis) is associated with potential serious risks.

Q: How does Megestol work to help with loss of appetite?

A: The drug works as an appetite stimulant, and official documents note its association with patterns of weight change. This action is linked to the medicine's ability to act on glucocorticoid receptors, influencing neuroendocrine systems that regulate energy balance.

Q: Do studies suggest Megestol is effective for improving weight?

A: Studies have examined the medicine's role in involuntary weight loss and appetite issues. Official evidence indicates that individuals in the research groups were associated with patterns of change in both appetite and total body weight over the study period.

Q: What is the difference between Megestol tablets and oral suspension?

A: Megestol is available in both tablet and liquid oral suspension forms. While tablets are often used for hormone-sensitive conditions, the higher-concentration oral suspension is typically labeled for once-daily use for indications like AIDS-related cachexia/anorexia.

Q: Does long-term use of Megestol have different side effects than short-term use?

A: Yes, official warnings note that certain serious risks are associated with chronic, or long-term, use. These include the potential for new-onset diabetes, Cushing’s syndrome, and adrenal insufficiency. These risks are also highlighted during the period of withdrawal from chronic use.

Q: Do high doses of Megestol have specific risks mentioned in official sources?

A: Official documents mention that pituitary-adrenal suppression is a frequent occurrence in patients undergoing chronic treatment. This chronic therapy, often involving higher doses for conditions like appetite loss, is associated with the need for surveillance regarding this potential suppression.

Q: Is Megestol a type of hormone replacement therapy?

A: Megestol is classified as a synthetic hormonal agent and specifically as a progestin (a type of progestational hormone). Its approved uses are centered on treating certain advanced cancers and managing appetite loss or significant weight wasting, not general hormone replacement therapy.

Q: Can Megestol be used for purposes other than the main listed conditions?

A: The uses for Megestol are specifically listed in the official labeling, which include advanced breast or endometrial cancer and AIDS-related appetite loss. Official US labeling states that the use of this medicine for other types of cancer is not recommended.

Q: Does taking Megestol affect laboratory test results?

A: Yes, official information indicates that the drug has been associated with changes in glucose tolerance, which can lead to high blood sugar (hyperglycemia). Additionally, laboratory evaluations for adrenal insufficiency are addressed in the official prescribing information for certain patients.

Q: What happens if I miss a scheduled dose of Megestol?

A: Patient information typically indicates that a missed dose is to be skipped entirely. Following this, the administration schedule is typically returned to the regular pattern, and the instruction is not to administer two doses simultaneously.

Q: Can a person stop taking Megestol suddenly?

A: Official warnings describe the potential for adrenal insufficiency (a problem with the body's stress response system) in patients who are being withdrawn from chronic therapy. This risk is highlighted particularly during times of stress.

Q: What is the purpose of the different strengths or forms of Megestol?

A: Megestol is supplied in both tablet and liquid oral suspension forms, which are associated with different approved uses and dosing patterns. The tablet form is indicated for advanced breast or endometrial cancer, while the higher-concentration oral suspension is typically reserved for appetite loss or weight wasting.

Q: Does Megestol have any common side effects related to the skin?

A: Adverse event reports list several side effects affecting the skin. These include experiencing a skin rash, pruritus (itching), and alopecia (hair loss).

Q: Does Megestol affect fertility in men or women?

A: Official information indicates that the medicine has the potential to cause reversible infertility in men and premenopausal women. This is due to its antigonadotropic effects, which means it influences the hormones involved in reproduction.

Q: Is there a generic version of Megestol available?

A: Yes, the active substance Megestrol Acetate is available in FDA-approved generic tablet forms in the United States.

Q: What kind of monitoring is often done when a person is taking Megestol?

A: Official labeling mentions that close patient surveillance is appropriate, particularly when treating cancer. Monitoring activities, such as checking renal function and laboratory evaluation for adrenal insufficiency, are addressed in the prescribing information for specific patient groups.

Q: Are there any restrictions on driving or operating machinery while taking Megestol?

A: Due to potential side effects on the nervous system, such as feeling confused or lethargic, patient safety information addresses the need for caution. Warnings state that if a patient experiences sleepiness or tiredness, they are generally advised in patient safety information not to operate machinery or drive.

Q: What official health bodies approve the use of Megestol?

A: Information regarding the medicine is maintained and regulated by official bodies in various territories. These include the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).

Q: Why is Megestol sometimes described as a palliative treatment?

A: The medicine is formally described as a palliative treatment in official labeling. This means it is indicated for managing the symptoms and functional limitations associated with advanced conditions, specifically advanced breast cancer and advanced endometrial carcinoma.

Q: Can Megestol cause fluid retention or swelling?

A: Yes, adverse event reports include edema (swelling). As a progestogen, the medicine has been associated with fluid retention, which is listed as a potential disease interaction in the official safety information.

How should Megestol be stored and disposed of?

Storage and Disposal of Megestrol

Storage Requirements

Megestrol Acetate must be stored at Controlled Room Temperature, specifically maintained between 20 to 25 C (68 to 77 F), to ensure stability as defined by regulatory standards. The medication must be kept in its container, tightly closed, and protected from environmental factors. The oral suspension must be kept from freezing and shielded from heat, moisture, and direct light. For safety, the product should be stored out of the reach of children, and tablets are dispensed with a child-resistant closure.

Disposal Instructions

Unused or expired Megestrol Acetate must be disposed of properly according to applicable laws and regulations. The primary method for disposal is through official drug take-back locations or specialized collection programs. If a take-back option is unavailable, the medication should be mixed with an undesirable substance, such as dirt or cat litter, sealed in a bag, and then discarded with household trash; tablets should not be crushed.

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

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