Prostanil

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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 Prostanil

What is Prostanil? (Finasteride)

Property Description
Active Ingredient Finasteride
Form Oral Tablet
Pharmacological Class 5-Alpha Reductase Inhibitor (5-ARI)
General Purpose Managing Dihydrotestosterone (DHT)-dependent conditions
Origin Synthetic (4-azasteroid compound)

Prostanil is a prescription-only medicine containing the active ingredient Finasteride, which is classified pharmacologically as a 5-Alpha Reductase Inhibitor (5-ARI). This designation indicates the drug’s function as a specific modulator of hormonal processes within the body. Chemically, Finasteride is a synthetic 4-azasteroid compound, meaning it is a man-made molecule derived from a steroid structure that is clinically recognized for its systemic effects on male hormone regulation. The drug is formulated as an oral tablet, enabling systemic administration after swallowing.


How Does the 5-Alpha Reductase Inhibitor Class Work?

This class of medicine achieves its purpose by blocking a key enzyme (5-alpha reductase) that is primarily responsible for generating the hormone Dihydrotestosterone (DHT) in critical tissues. By interfering with this enzyme, the medicine causes a significant reduction in the total concentration of DHT in the body. The general therapeutic purpose of this hormonal suppression is to address conditions that are known to be DHT-dependent in adult males. Finasteride works by decreasing the amount of a natural hormone that causes growth of the prostate, suggesting the medicine helps regulate hormonal signals contributing to tissue changes.


Distinguishing Finasteride from Other Related Compounds

Finasteride is primarily distinguished by its high degree of selectivity for the Type II 5α-reductase isoenzyme, which is the predominant form found in key therapeutic target areas. Finasteride selectively inhibits the intracellular enzyme 5α-reductase. This selective inhibition profile means the drug’s primary action is concentrated on the enzyme type most relevant to its general purpose. This focus is a key differentiating factor, setting Finasteride apart from dual-acting inhibitors which block both Type I and Type II isoenzymes, thereby ensuring a particular utility in providing a targeted intervention.

Regulatory References

  1. MedlinePlus - Finasteride (National Institutes of Health)

What side effects are possible with Prostanil?

Possible Side Effects and Safety Information

The official safety profile for Finasteride, the active ingredient in Prostanil, is structured by regulatory authorities to classify potential adverse reactions based on the physiological systems affected and their frequency of occurrence. The majority of documented side effects relate to the reproductive system, reflecting the medicine's mode of action as a 5-Alpha Reductase Inhibitor.

Officially Documented Adverse Reactions

The adverse reactions listed in official regulatory documents are categorized based on their observed frequency in clinical trials and post-marketing surveillance:

Classification System-Organ-Class Focus Examples from Regulatory Labeling
Common (ge 1%) Reproductive system Decreased libido, Erectile dysfunction, Ejaculation disorder (including decreased volume)
Uncommon (0.1% to <1%) Breast, Skin, Psychiatric Gynecomastia (breast enlargement), Rash, Depressed mood
Frequency Not Known Psychiatric, Reproductive, Immune Suicidal ideation, Testicular pain, Hypersensitivity reactions (e.g., angioedema)

Serious Safety Considerations

Regulatory authorities highlight certain serious safety concerns. These include the documented risk of male breast cancer and the increased risk of high-grade prostate cancer, which has been observed in clinical trials with the 5 mg dose. Additionally, the label notes that certain sexual side effects may persist after discontinuation of treatment.

Population-Specific Constraints

The medicine is contraindicated for use in women, particularly those who are pregnant or may become pregnant, due to the risk of abnormal development of a male fetus's external genitalia. The official prescribing information also mandates that for men undergoing Prostate-Specific Antigen (PSA) testing, the laboratory values must be doubled for comparative purposes, as the drug causes a predictable reduction in serum PSA concentration.

Overdose and Emergency Response

Overdose and When to Seek Help — Official Regulatory Information for Prostanil

This section details the officially documented overdose profile for the active ingredient, Finasteride, based strictly on the Overdosage sections of government regulatory documents.

Element Official Regulatory Statement
Documented Manifestations Clinical studies involving single doses up to 400 mg and multiple doses up to 80 mg/day for three months did not result in specific dose-related undesirable effects in human patients.
Specific Treatment/Antidote No specific treatment or antidote is officially recommended for an overdose. Management is supportive until further experience is obtained in acute toxicity cases.

Mandatory Emergency Actions

Element Label-Derived Phrasing
Action Mandate Seek immediate medical attention or call a Poison Help line.
Help-Seeking Condition This action is required even if there are no signs of discomfort or poisoning apparent to the individual, as mandated by regulatory agencies.

Resulting Overdose Structure

Official overdose statements:

  • The lack of an observed acute toxicity syndrome means no specific severity classification is assigned to Prostanil overdose in the official label.
  • The explicit statement that no specific treatment is recommended highlights the need for immediate professional guidance in all suspected overdose events.

Connection to the overall overdose profile: The regulatory documents define the overdose profile by the absence of a defined symptomatic picture and the lack of a specific medical protocol. The primary official mandate is therefore focused entirely on requiring immediate contact with emergency medical services as the definitive action for any suspected exposure exceeding the prescribed amount, regardless of the individual's clinical presentation.

Therapeutic Uses of Prostanil

Prostanil is commonly used in situations involving certain distressing symptoms and functional stress within the domain of urological health.

Symptomatic Relief for Lower Urinary Tract Issues (LUTS)

This therapeutic area is relevant for managing symptoms that interfere with daily comfort and create noticeable physiological strain. It is considered relevant in contexts marked by increased discomfort or tension related to voiding and storage symptoms. This class of medication is relevant for managing symptoms associated with benign prostatic hyperplasia (BPH) and related conditions.

Prostanil may assist with managing symptom clusters that may become intense or disruptive, such as a weak stream, incomplete emptying, urgency, and the frequent need to urinate at night (nocturia). This supports patients during difficult episodes by easing distress and may contribute to improved comfort during periods of heightened symptoms. The medication is commonly used across conditions characterized by episodic or fluctuating symptom patterns.

Management of Chronic Discomfort and Functional Strain

Prostanil is applied across domains where additional symptomatic support is needed when symptoms related to inflammatory or irritative states interfere with daily functioning. This supports managing symptoms related to physical discomfort, such as pelvic or perineal aches, associated with conditions involving inflammatory or irritative processes. The medication may provide supportive relief when symptoms intensify and short-term symptomatic assistance is needed.


Quick Fact: Support for Nocturia (Contributes to easing the overall symptom load by supporting patients during episodes of heightened discomfort from night-time urinary frequency.)

Regulatory References

  1. NIH MedlinePlus overview of alpha-blockers

Eligibility and Restrictions for Use

Who Can and Cannot Use Prostanil?

Official regulatory documents define specific populations who are eligible for Prostanil and those for whom use is strictly prohibited.


Eligible and Conditional Populations

Prostanil is only indicated for use in adult males. For older adults, no dosage adjustment is necessary, and its usefulness is not limited by geriatric-specific problems. Patients with renal impairment also require no dosage adjustment, confirming their eligibility under standard conditions.

Caution is advised for patients with liver function abnormalities because the medicine is metabolized extensively by the liver. The medicine is not indicated for use in women who are breastfeeding.


Contraindicated Populations

Prostanil is strictly contraindicated in several groups. It must not be used in females, particularly those who are or may become pregnant, due to the risk of abnormal development in a male fetus. It is also contraindicated in pediatric patients (under 18 years of age), as safety and effectiveness have not been established in this age group. Use is prohibited for individuals with a known hypersensitivity to the active ingredient or any components of the tablet. Additionally, patients with certain hereditary problems, such as galactose intolerance or total lactase deficiency, should not take this medicine.

What should I know about interactions with other medicines?

Prostanil Interactions with other medicines and products


Interaction Scope

Prostanil (Tamsulosin Hydrochloride) is subject to interactions primarily concerning its metabolism and blood pressure-lowering effects.

Medicinal Product Categories with Documented Interactions:

  • Other alpha1-adrenoceptor antagonists.
  • Strong and moderate inhibitors of Cytochrome P450 (CYP) enzymes, specifically CYP3A4 and CYP2D6.
  • Medicines that affect blood pressure, including Alpha-Blockers.

Specific Interacting Medicines (if explicitly listed):

  • Strong CYP3A4 Inhibitors (e.g., ketoconazole): Concomitant use with strong CYP3A4 inhibitors is classified as a significant interaction that substantially increases tamsulosin exposure.
  • Strong CYP2D6 Inhibitors (e.g., paroxetine): Concomitant use with strong CYP2D6 inhibitors may lead to increased tamsulosin exposure.
  • Cimetidine: Concurrent administration results in a rise in tamsulosin plasma levels.
  • Furosemide: Concurrent administration results in a fall in tamsulosin plasma levels.
  • Diclofenac and Warfarin: These may increase the elimination rate of tamsulosin.

Interaction-Related Restrictions

Interaction Severity Classification (as defined in official documents):

  • Combinations with strong CYP3A4 and CYP2D6 inhibitors may be classified as combinations to be used with caution or, in some regulatory contexts, avoided entirely depending on the inhibitor's strength, due to the potential for significant increases in tamsulosin systemic exposure.
  • The use of Prostanil in combination with other alpha1-adrenoceptor antagonists may lead to hypotensive effects (reduction in blood pressure).

Timing-Based Interaction Rules (if applicable):

  • No explicit spacing or timing requirements are mandated for most common interacting agents (like atenolol, enalapril, or nifedipine), as no clinically significant interactions were observed in studies with these agents.

Official Interaction Statements

  • The concurrent administration of other alpha1-adrenoceptor antagonists could potentiate the hypotensive effect of Prostanil.
  • Co-administration with potent inhibitors of CYP3A4 or CYP2D6 is documented to increase systemic exposure of Prostanil, and use must be monitored.
  • The documented effects of cimetidine (rise in levels) and furosemide (fall in levels) on Prostanil plasma concentrations are noted, although a posology change is not generally required as levels are indicated to remain within the normal range.

Connection to the overall interaction profile (2–4 sentences): The official interaction profile for Prostanil is structured around two key pharmacological constraints: the risk of increased blood pressure lowering when combined with other alpha1-blockers and the pharmacokinetic risk associated with inhibiting the primary metabolic pathways, CYP3A4 and CYP2D6. Regulatory documents detail that combining Prostanil with strong inhibitors of these enzymes significantly alters drug exposure, necessitating careful consideration to manage the potential for adverse effects or loss of efficacy.

Mechanism of Action

Selective Enzyme Inactivation

Prostanil functions as a specific and competitive inhibitor targeting the Type II 5-alpha reductase enzyme, which is concentrated in key peripheral tissues. By binding to this enzyme and forming a stable complex, the drug effectively blocks the metabolic conversion of Testosterone into the more potent androgen, Dihydrotestosterone (DHT), which is the necessary molecular step for its downstream physiological effect.

Profound Androgen Signal Suppression

The central mechanism of action is the resulting sustained reduction of DHT concentration—up to 70% systemically and over 90% locally in tissues—which reduces the androgenic growth-stimulating hormonal signal. This withdrawal of the androgenic stimulus on sensitive cells leads to subsequent cellular regression and the reduction of DHT-driven tissue mass over time.

Cascade of Delayed Physiological Change

The drug's cascade creates a temporal separation: the molecular suppression of DHT is rapid (within 24 hours), but the resultant physiological change of tissue regression and volume decrease is a slow, chronic process requiring months of continuous hormonal blockade to manifest. This effect is entirely reversible, as discontinuation allows DHT levels to return to baseline, demonstrating the mechanism's dependency on continuous action.

Dosage and Administration Information

How to Use Prostanil: Official Administration Guidelines

Prostanil (Finasteride) is a prescription-only medicine administered as a film-coated oral tablet. Its proper use is defined by standardized dosing regimens and administration rules.


Standard Dosing and Schedule

The medicine is taken once daily (qDay) in two officially established dosage strengths:

Clinical Context Recommended Dose
Benign Prostatic Hyperplasia (BPH) 5 mg once daily
Androgenetic Alopecia 1 mg once daily

Administration may be done with or without food, and should be consistent by taking the dose at approximately the same time each day. Treatment is typically long-term; for certain conditions, daily use for at least three to six months is necessary to observe and maintain the documented effects.


Administration Procedure and Population Rules

The Prostanil tablet must be swallowed whole with water and must not be crushed, broken, or chewed. If a dose is missed, standard protocol suggests skipping the missed dose and resuming the regular dosing schedule; doses should not be doubled to compensate for a missed dose.

Official labels confirm that no dosage adjustment is required for older adults (geriatric use) or in patients with renal impairment. The product is not indicated for use in the pediatric population.

Recent Clinical Evidence

Research evidence / Overview of studies for Prostanil

Evidence for Use in Managing Benign Prostatic Hyperplasia (BPH) and LUTS

The evidence base for Prostanil's use in BPH is derived primarily from large-scale, multi-year Randomized, Controlled Trials (RCTs), representing a high level of evidence according to regulatory summaries. This research approach describes what has been observed so far in controlled settings. Systematic reviews and meta-analyses have also contributed to the evidence landscape.

Research examined outcomes related to physical discomfort and functional imbalance associated with BPH in adult men. Studies evaluated changes in patient-reported symptom scores (like IPSS), objective disease markers such as measured changes in prostate gland volume, and clinical progression endpoints, including the incidence of acute urinary retention and the requirement for BPH-related surgical procedures. In trials assessing short-term symptom patterns, findings indicated that the difference in symptom scores measured versus placebo was sometimes small, and observed changes emerge slowly.

The Landscape of Long-Term Studies and Follow-up

The evidence base includes primary trials typically conducted over two to four years, as well as long-term open-label extension studies. These extensions provide context on how patients reported their experience over the intermediate-term. Data for long-term effects are not fully established when comparing Prostanil against a placebo beyond the initial several years.

Evidence Profile in Specific Study Groups

Prostanil was studied in adult men, generally aged 50 and older, who had BPH. Evidence indicates that results apply most consistently to the populations studied—meaning men with a measurably enlarged prostate gland. Data for certain groups, such as those with smaller prostate volumes, remain insufficient to draw similar conclusions.

What the Research Indicates Is Still Uncertain

Key limitations include the fact that the rate of change measured in patient symptoms was observed to be slower. Subgroup findings are uncertain for men with less prostate enlargement, and there is limited information for long-term outcomes based on placebo-controlled data beyond the intermediate phase of the initial trials. The existing study results reflect the specific conditions under which they were conducted.

Key Studies & References Serum prostate-specific antigen and prostate volume predict long-term changes in symptoms and flow rate: results of a four-year, randomized trial comparing finasteride versus placebo. PLESS Study Group

Frequently Asked Questions (FAQ)

Common questions about Prostanil (FAQ)

Q: How quickly should I expect to see an effect from Prostanil?

A: Studies indicate that the reduction in the target hormone, Dihydrotestosterone (DHT), happens rapidly. However, the official product information notes that the subsequent physical changes, such as symptom improvement or tissue decrease, are gradual. Regulatory documents indicate that continuous daily use for at least three to six months is typically required to observe and maintain the documented physiological changes.


Q: Does Prostanil start working right away?

A: Regulatory documents indicate that, on a molecular level, the effect begins rapidly by suppressing the target hormone within 24 hours of the first administration. However, the resulting beneficial effects that a patient might feel on the body are a slow process that requires continuous therapy over several months.


Q: Do the side effects of Prostanil usually go away after a while?

A: Clinical trial data generally reflect that most reported side effects resolve following the cessation of therapy. However, the official safety profile notes that certain sexual side effects may be prolonged and persist even after discontinuation of treatment. If any reactions are concerning or persistent, it is important to discuss them with a healthcare provider.


Q: Is it okay to stop taking Prostanil suddenly?

A: Research indicates that the drug’s physical effect on tissues is entirely reversible, meaning the hormonal levels that the drug suppressed return to baseline after discontinuation. Since the medicine's effect is dependent upon continuous action, it is recommended that patients consult with their prescribing physician before making any change to their therapy schedule.


Q: Is Prostanil a common medication, or is it new?

A: Prostanil's active ingredient, Finasteride, has been approved by major regulatory agencies for various uses since the 1990s. Government data indicates the medicine has been widely available and used by patients for decades across many countries.


Q: Is Prostanil the same type of drug as [Similar Drug Name]?

A: Prostanil is classified pharmacologically as a 5-Alpha Reductase Inhibitor. Regulatory documents define this class by its targeted action: specifically inhibiting the Type II isoenzyme to reduce Dihydrotestosterone (DHT). This specific mechanism of action distinguishes it from other classes of medicine used for similar conditions.


Q: What's the difference between Prostanil and other drugs that treat the same condition?

A: The official mechanism of action defines Prostanil's purpose as inhibiting the Type II 5-alpha reductase enzyme to achieve hormonal suppression. This sets it apart from other types of treatments for the same conditions that may rely on different pharmacological pathways, such as medications that relax muscles or nerves.


Q: Why do doctors prescribe Prostanil instead of another treatment?

A: Regulatory agencies authorize the drug for its ability to target the hormonal process responsible for the condition. Its documented utility includes symptom improvement, reducing the risk of acute urinary retention, and lowering the risk of surgery for BPH. This indication profile defines its recognized utility.


Q: What are the most serious side effects I should know about?

A: Official documents highlight several serious safety concerns that users should be aware of. These include the documented risk of male breast cancer and an increased risk of high-grade prostate cancer observed with the higher dose. Additionally, sexual side effects that may persist after discontinuation are noted as a serious consideration in the official warnings.


Q: Does Prostanil affect my blood pressure?

A: Clinical studies found that Prostanil, when administered alone, generally had no effect on blood pressure in the patients studied. However, regulatory documents warn that combining it with other alpha1-blockers could potentiate hypotensive effects (a significant reduction in blood pressure).


Q: How long does Prostanil stay in your system after you stop taking it?

A: Pharmacokinetic studies report that the half-life of Prostanil in the bloodstream is typically between 4.7 and 8 hours in adult men. The half-life refers to the time it takes for half of the drug substance to be eliminated from the body. Therefore, the medication itself is largely cleared from the system within a few days.


Q: Does Prostanil interact with common pain relievers like ibuprofen?

A: Official regulatory documents do not specifically list common over-the-counter pain relievers such as ibuprofen as interacting medicines. The primary warnings focus on prescription medicines that affect blood pressure or inhibit specific liver enzymes (CYP3A4/2D6) involved in its processing.


Q: Are there any common supplements, like vitamins, that interact with Prostanil?

A: Official guidance documents emphasize that insufficient information exists regarding the safety of combining Prostanil with most complementary medicines, herbal remedies, or supplements. This is because these products are often not studied in the same way as prescription drugs.


Q: Is Prostanil a controlled substance?

A: No. Official regulatory classifications confirm that Finasteride, the active ingredient in Prostanil, is not classified as a controlled substance by drug enforcement agencies. Controlled substances are regulated due to their potential for abuse or dependence.


Q: What is the typical age range of people who use Prostanil?

A: Prostanil is indicated for use only in adult males. Clinical trial data reflects that the medicine was studied in men aged 18 to 41 for hair loss and primarily in men aged 50 years and older for prostate conditions.


Q: Is there a warning about using Prostanil before driving?

A: Official safety documents list adverse reactions such as dizziness and have included instances of fatigue in post-marketing reports. Regulatory guidance often advises caution when performing activities that require concentration, such as driving, if a user experiences these specific effects.


Q: Can I take Prostanil while on an antibiotic?

A: Some antibiotics are known to inhibit a specific enzyme, CYP3A4, which helps the body process Prostanil. Combining with strong inhibitors of this enzyme carries the risk of increased Prostanil exposure. This interaction requires discussion and monitoring by a healthcare professional.


Q: How is Prostanil different from a placebo in clinical studies?

A: Clinical trial results published in regulatory documents showed that, compared to a placebo (a sugar pill), Prostanil demonstrated statistical differences in key outcomes. These included improvements in patient-reported symptoms, measurable reduction in prostate volume, and a decreased incidence of severe clinical outcomes.


Q: Does Prostanil require any specific monitoring or lab tests?

A: Official information mandates that for men undergoing routine Prostate-Specific Antigen (PSA) testing, the laboratory value must be doubled for comparative purposes. This is because the drug causes a predictable, non-disease-related reduction in the serum PSA concentration.


Q: Is there a generic version of Prostanil available?

A: Yes. Regulatory agencies have approved the active ingredient, Finasteride, as a generic drug. Generic versions are approved after confirming that they are bioequivalent to the brand-name product.


Q: Does Prostanil affect sleep?

A: Official safety documents list depressed mood as an uncommon side effect. Additionally, post-marketing reports have included instances of insomnia and fatigue related to its use.


Q: Is Prostanil mainly used for short-term or long-term treatment?

A: Regulatory documents describe treatment with Prostanil as typically long-term. For conditions such as BPH, continuous daily use for at least three to six months is stated as necessary to achieve and maintain the documented physiological effects.


Q: What is the half-life of Prostanil?

A: The half-life of the drug in the bloodstream is reported to be between 4.7 and 8 hours in adult men. This pharmacokinetic data point is an estimate and may vary slightly, particularly in older adults.


Q: Are there different forms of Prostanil (e.g., tablet, capsule, liquid)?

A: Prostanil is officially approved and formulated as a single dosage form: a film-coated oral tablet. It is available in two distinct dosage strengths for its indicated uses.


Q: Is Prostanil safe to use with alcohol?

A: Official regulatory documents do not list alcohol as a direct drug interaction. However, some clinical guidance notes that heavy alcohol consumption may potentially interfere with the medicine's protective effects against low-grade prostate cancer.


Q: What does the term 'efficacy' mean in relation to Prostanil research?

A: In the context of regulatory drug research, 'efficacy' refers to the demonstrated effectiveness of Prostanil in achieving its intended clinical goals. This is measured by comparing the medicine's impact on patient symptoms or objective markers against a control group in clinical trials.


Q: Is it normal to feel a bit tired when starting Prostanil?

A: Tiredness, or fatigue, is not listed among the commonly reported side effects in clinical trials. However, post-marketing reports collected by regulatory agencies have included instances of fatigue associated with the use of the medicine.


Q: Is Prostanil considered a high-risk medication?

A: Regulatory documents include specific warnings about serious safety considerations, such as the risk of male breast cancer and the increased risk of high-grade prostate cancer with the higher dose. The presence of these warnings underscores that the benefits and risks of Prostanil require careful evaluation and monitoring.


Q: What should I know about Prostanil if I have allergies?

A: Prostanil is strictly contraindicated (meaning it should not be used) in individuals who have a known hypersensitivity or allergic reaction to the active ingredient, Finasteride, or any of the inactive components used to make the tablet.

How should Prostanil be stored and disposed of?

Official Storage and Disposal Requirements

Prostanil (Finasteride) tablets must be stored at room temperature, away from excess heat and moisture. The medicine must always be kept in its original container and the lid must be tightly closed to maintain product stability.


Special Handling and Safety:

  • The product must be stored out of the sight and reach of children.
  • Pregnant or potentially pregnant women must not handle crushed or broken tablets due to the risk of fetal harm.

Disposal:

Any unused or expired Prostanil must be disposed of in accordance with local requirements. Tablets should not be flushed down the toilet or poured into drains, but should be discarded safely following local guidelines for household medicine waste.

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

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