Sildena

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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 Sildena

Property Description
Active ingredient Sildenafil (as Sildenafil citrate)
Form Tablet, Injectable solution, Powder for oral suspension
Pharmacological class Phosphodiesterase type 5 (PDE5) inhibitor
General purpose Improving localized blood flow dynamics
Origin Synthetic organic compound

What Type of Medicine is Sildena and How is it Classified?

Sildena is a prescription-only medication featuring the active pharmaceutical ingredient sildenafil, which is formally classified as a Phosphodiesterase type 5 (PDE5) inhibitor. Sildenafil is a synthetic organic compound. This categorization places it within a defined group of medications whose mechanism has been clinically recognized for selectively modulating enzyme activity within the body. Sildenafil's action is based on this selective enzyme inhibition.

Composition and Available Forms of Sildenafil

The core composition of the Sildena preparation relies on sildenafil—frequently supplied as the salt sildenafil citrate—as the single active ingredient. This single-component nature simplifies its profile compared to combination drugs. Sildenafil is notably available across multiple official dosage forms, including standard tablets for oral use, an injectable solution for intravenous administration, and a powder for oral suspension. This wide variation in route of administration is a key feature that allows the active ingredient to be adapted for different patient needs.

General Purpose and High-Level Action

The general purpose of Sildena is to improve localized blood flow by enhancing the natural processes that lead to smooth muscle relaxation within blood vessel walls. This effect is achieved because the drug acts as a selective enzyme blocker, targeting PDE5 to temporarily prevent the rapid degradation of a signaling molecule. By mediating controlled vasodilation in targeted circulatory pathways, the medication supports functions where robust and sustained blood flow dynamics are essential.

Regulatory References

  1. MedlinePlus Drug Information

What side effects are possible with Sildena?

The safety profile of Sildena, containing the active substance Sildenafil, is officially classified based on the incidence of adverse reactions documented in government regulatory sources.

Common and Very Common Adverse Reactions

The most frequent adverse event documented is headache, which is classified as Very Common (occurring in more than 1 in 10 users). Other frequently reported effects, classified as Common, include flushing (reddening of the face and neck), dyspepsia (indigestion), nasal congestion, and abnormal vision, which may involve a color tinge to vision or blurred sight. Reactions affecting the musculoskeletal system, such as back pain and muscle pain, are also listed as Common.

Serious Adverse Reactions and Restrictions

Regulatory documents highlight several serious adverse reactions, though these are less common. These include priapism (a prolonged erection lasting more than four hours), sudden decrease or loss of vision (e.g., non-arteritic anterior ischemic optic neuropathy or NAION), and sudden decrease or loss of hearing. Serious cardiovascular events, such as myocardial infarction (heart attack) and stroke, have also been documented in the post-marketing phase.

The medicine is strictly contraindicated (prohibited) for use with any form of organic nitrates or the guanylate cyclase stimulator riociguat due to the risk of severe safety consequences. Specific safety caution is also noted for patients with severe hepatic impairment, severe renal impairment, and certain cardiovascular conditions, as its use may be associated with altered risk in these populations.

Overdose and Emergency Response

Overdose and when to seek help

Official regulatory documents specify that taking doses of Sildena significantly higher than recommended may lead to an escalation of documented adverse events. Following high exposure, effects similar to those seen at therapeutic doses—such as headache, facial flushing, and dyspepsia—were observed but with notably increased rates and severities.

The required management for overdose is strictly symptomatic and supportive, as official labeling confirms that no specific antidote is known for Sildenafil. Furthermore, clearance through renal dialysis is not expected to be effective, a factor attributed to the medication’s high degree of plasma protein binding.

Urgent medical attention is required for specific, time-critical manifestations documented in prescribing information. Patients must seek immediate medical assistance if they experience a prolonged erection lasting longer than four hours, a condition that necessitates prompt intervention to mitigate the risk of permanent tissue damage. Medical care must also be sought promptly in the event of a sudden loss of vision or a sudden decrease or loss of hearing. Finally, regulatory warnings highlight a population-specific risk, stating that doses higher than those recommended should not be used in pediatric patients with pulmonary arterial hypertension due to a documented increased risk of mortality.

Therapeutic Uses of Sildena

What Sildena Treats: Main Uses and Benefits

Sildena is commonly used in situations involving certain distressing symptoms, primarily across two distinct therapeutic domains. The medicine is applied in these two major contexts to provide supportive relief.

The medication is relevant for easing symptom clusters that may become intense or disruptive in two main conditions: erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). It supports patients during episodes of heightened discomfort and contributes to easing the overall symptom load when symptoms interfere with routine activities.

“Applied across domains where additional symptomatic support is needed.”


Quick Fact: Relief for Physical Discomfort

Sildena is used in conditions presenting with systemic or localized discomfort and is applied in scenarios where additional symptomatic assistance is needed, especially when temporary functional strain or discomfort is present.

Regulatory References

  1. NIH MedlinePlus overview

Eligibility and Restrictions for Use

Who can and cannot use Sildena?

Sildena (sildenafil) eligibility is strictly defined by regulatory authorities and depends heavily on a patient's existing health conditions and concomitant medications.

Absolute Contraindications (Must Not Use)

The medicine is contraindicated in patients receiving any form of nitrates (e.g., nitroglycerin) or soluble guanylate cyclase (sGC) stimulators (e.g., riociguat). Use is also prohibited for individuals with severe hepatic impairment (Child-Pugh Class C), a recent history of stroke or myocardial infarction (within six months), or severe hypotension (blood pressure < 90/50 mmHg). Specific eye conditions, such as Non-Arteritic Anterior Ischaemic Optic Neuropathy (NAION) or retinitis pigmentosa, also render a patient ineligible.

Age and Conditional Use

For the Erectile Dysfunction (ED) indication, Sildena is not indicated for individuals below 18 years of age. Eligibility is conditional for older adults (ge 65 years) and those with severe renal impairment or mild to moderate hepatic impairment, for whom a lower starting dose is considered according to labeling. For the Pulmonary Arterial Hypertension (PAH) indication, pediatric use is permitted but carries a regulatory warning against using higher than recommended doses. The medicine is not indicated for women for the ED purpose.

What should I know about interactions with other medicines?

Sildena Interactions with other medicines and products

Interactions with Sildena (sildenafil) are categorized based on their severity and mechanism, as documented in official government regulatory information.


Formally Contraindicated Combinations

Co-administration with the following substances is strictly prohibited due to the risk of severe, potentially fatal hypotension (dangerously low blood pressure), reflecting an additive vasodilatory effect:

  • Organic Nitrates and Nitric Oxide Donors (in any form).
  • Guanylate Cyclase Stimulators (e.g., riociguat).

Documented Pharmacokinetic Interactions

Sildena is metabolized primarily by the liver enzymes CYP3A4 and, to a lesser extent, CYP2C9. Substances that inhibit these enzymes can significantly alter Sildena exposure.

Interacting Substance/Class Official Exposure Change
Ritonavir (Potent CYP3A4 Inhibitor) Sildenafil exposure ( AUC) increased by approximately 1,000% (11-fold).
Ketoconazole, Erythromycin Sildenafil plasma levels are documented to increase.
Bosentan (CYP3A4 Inducer) Sildenafil plasma levels are documented to decrease.

Pharmacodynamic and Other Constraints

  • Alpha-Blockers (e.g., tamsulosin, doxazosin) may potentiate Sildena’s hypotensive effects. Regulatory documents note that symptomatic hypotension is most likely to occur within 4 hours post-Sildena dosing. Patients must be hemodynamically stable on alpha-blocker therapy before starting Sildena.
  • Interactions are noted with alcohol and grapefruit products.
  • In patients with Hepatic Impairment, Sildena clearance is reduced, which can increase exposure and the risk of interactions.

Mechanism of Action

Targeted Inhibition of the PDE5 Enzyme

Sildenafil functions primarily as a selective competitive inhibitor of the enzyme Phosphodiesterase type 5 (PDE5), a key regulatory component found in specific vascular smooth muscle cells. This targeted interaction prevents PDE5 from performing its function of breaking down the intracellular messenger cyclic Guanosine Monophosphate (cGMP). This molecular event is the foundation of the drug's mechanism, leading directly to the accumulation of cGMP in the affected tissues.


Amplification of the NO/cGMP Signaling Cascade

The drug's mechanism is fundamentally an amplification of the body's natural signaling cascade, specifically the Nitric Oxide (NO) / cGMP pathway. Sildenafil enhances this pathway by preventing the degradation of cGMP, thereby extending the duration and intensity of the signal initiated by endogenous Nitric Oxide release. This process ensures the drug's effect is localized and dependent on a preceding physiological stimulus.


Modulation of Localized Vascular Smooth Muscle Tone

The sustained elevation of cGMP directly triggers an enzyme cascade that facilitates the relaxation (vasodilation) of the smooth muscle lining the blood vessels by reducing intracellular calcium levels. This physiological adjustment of vascular smooth muscle tone leads to an increase in localized blood flow dynamics and perfusion pressure in the target region, which is the mechanism's final physiological consequence.

Dosage and Administration Information

How to Use Sildena: Official Administration Guidelines

Sildena (sildenafil) is used according to two distinct, officially labeled protocols: an intermittent, as-needed regimen and a continuous, three-times-daily regimen (TID). Dosing and administration route are determined by the specific approved use.


Administration Routes and Forms

Administration is primarily oral using tablets or a powder for oral suspension. An intravenous (IV) solution is an approved alternative, strictly for temporary use when a patient in the continuous regimen cannot take the medicine by mouth. The oral forms include 25 mg, 50 mg, and 100 mg tablets for intermittent use, and 20 mg tablets for the continuous regimen. The IV dose of 10 mg is considered pharmacologically equivalent to a 20 mg oral dose.


Dosing Patterns and Frequency

Usage Pattern Standard Dose & Range Maximum Frequency
Intermittent Starts at 50 mg, adjustable between 25 mg and 100 mg. Once per day
Continuous (Oral) 20 mg three times a day (TID), titratable up to 80 mg TID. Three times per day

For intermittent use, the dose is taken 30 minutes to 4 hours before activity. Continuous use requires doses to be administered approximately 4–8 hours apart. If a continuous dose is missed, it is recommended to take it as soon as possible but do not double the dose.


Special Administration Considerations

The medicine may be taken with or without food for both usage patterns, although a high-fat meal may delay the onset of activity for intermittent use. For the intermittent regimen, a 25 mg starting dose should be considered for older adults (65 years and older) and those with severe renal or hepatic impairment.

Recent Clinical Evidence

Evidence for Use in Erectile Dysfunction (ED)

The research base for Sildena in erectile dysfunction relies primarily on short-term, placebo-controlled randomized controlled trials (RCTs). These studies explored how functional outcomes change over defined intervals in adult men with ED of various origins, including those with conditions like diabetes or following prostate surgery. Studies monitored patient-reported experiences using standardized tools like the International Index of Erectile Function (IIEF). Findings describe patterns observed in the studies where men using Sildena reported recorded changes in their IIEF scores compared to the groups receiving a placebo. The results apply only to the populations studied.

Evidence for Use in Pulmonary Arterial Hypertension (PAH)

Evidence for Sildena in pulmonary arterial hypertension (PAH) comes from intermediate-term randomized controlled trials (12 to 16 weeks). PAH is a condition marked by functional limitations. Researchers examined changes in the patients' exercise capacity, primarily the 6-Minute Walk Distance (6MWD), and monitored objective changes in hemodynamic parameters. Studies monitored recorded changes in the 6MWD test in patients using Sildena compared to the groups on placebo, and reported how functional status evolved in the observed populations.

Long-Term Evidence, Special Populations, and Research Gaps

Follow-up durations for the primary RCTs for both ED and PAH were generally limited, meaning data for long-term outcomes remains insufficient and sustained durability is not yet clear. Dedicated studies were observed in adults with ED linked to specific conditions and in children and adolescents with PAH. Findings describe patterns in these specific subgroups, but data for these specific groups remains insufficient due to smaller sample sizes, and evidence quality varies in the pediatric subgroup. Furthermore, comparative evidence against other similar treatments is lacking, and long-term effects on complex outcomes such as survival remain uncharacterized based on initial trials.

Key Studies & References

  1. Label: SILDENAFIL tablet - DailyMed (PAH)
  2. The International Index of Erectile Function (IIEF): A multidimensional scale for assessment of erectile dysfunction (BAUS)

Frequently Asked Questions (FAQ)

Common questions about Sildena (FAQ)


Q: How long does the effect of Sildena usually last in the body?

Official product information indicates that the effects of Sildenafil generally last for about four to six hours in most users. The exact duration can vary based on the prescribed amount and individual factors.


Q: Can Sildena be taken by women or is it only for men?

Sildena is not indicated for women when it is prescribed for Erectile Dysfunction. However, for the treatment of Pulmonary Arterial Hypertension (PAH), the active ingredient sildenafil is approved for use in both men and women under a different brand name and dosing protocol.


Q: Is Sildena suitable for use by older adults?

Sildena is generally suitable for use by older adults. Regulatory guidance specifies that a lower starting dose is typically considered for patients who are 65 years of age or older.


Q: Can Sildena affect sperm quality or fertility, according to research?

Core regulatory documents do not provide conclusive human data on Sildenafil's effect on sperm quality or fertility. Official prescribing information focuses primarily on the established indications and known safety warnings.


Q: Can Sildena be used by people with liver disease?

Official documents state that Sildena is contraindicated in patients with severe hepatic impairment (severe liver disease). For individuals with mild to moderate liver impairment, a lower starting dose is typically considered.


Q: If I miss a planned dose of Sildena, what does the official document say I should do?

For the continuous, scheduled regimen (used for PAH), regulatory instructions state that it may be taken as soon as remembered. However, it is advised not to double the next dose. Instructions for an intermittent, as-needed dose are not typically specified as it is taken only when intended.


Q: Are there any known issues with taking Sildena if someone has heart problems?

Sildena is formally contraindicated for people with certain serious heart issues, including a recent history of stroke or heart attack (within six months) and severe hypotension (very low blood pressure). Its use is subject to careful evaluation when specific cardiovascular conditions are present.


Q: Is Sildena addictive, or does it cause physical dependence?

Official regulatory texts, which list known adverse effects and contraindications, do not list addiction or physical dependence as known safety concerns associated with the drug’s use.


Q: Is it possible for Sildena to stop working after someone has used it for a long time?

Regulatory documents mention that follow-up durations for primary clinical trials were limited, meaning that data regarding long-term outcomes remains insufficient. The question of sustained effectiveness or durability over many years of use is not yet clearly characterized.


Q: Do people use Sildena for anything other than its main approved use?

Sildena is only formally approved by regulatory agencies for its specific indications (Erectile Dysfunction and Pulmonary Arterial Hypertension). Official documents do not address or endorse use for non-approved conditions.


Q: What kinds of food or drinks might affect how Sildena is absorbed?

Official instructions note that Sildena can be taken with or without food. However, a high-fat meal is documented to delay its absorption and the onset of its activity. Additionally, grapefruit products are noted to interact and are generally advised to be avoided.


Q: Is it true that taking Sildena on an empty stomach makes it work faster?

Official documents state that consuming the medicine with a high-fat meal may delay the onset of activity. This indicates that the quickest absorption is likely achieved when taken without food.


Q: What kinds of herbal supplements are known to potentially interact with Sildena?

Regulatory authorities advise that the safety of herbal remedies and supplements taken alongside Sildena cannot be confirmed through standard testing. Individuals are advised to disclose all supplements and remedies to a healthcare professional.


Q: Are there any specific safety warnings about Sildena and driving or operating machinery?

Official safety labels advise caution regarding driving or operating heavy machinery. This warning is due to the potential for side effects such as dizziness, headaches, and visual disturbances, which could temporarily impair a person's ability to perform these tasks.


Q: Is Sildena available without a prescription in some countries?

Sildena is a prescription-only medication in major markets like the US and Canada. However, regulatory bodies in some other countries have reclassified certain Sildenafil products for Erectile Dysfunction as an over-the-counter (OTC) or pharmacy medicine, meaning regulations differ internationally.


Q: What is the current regulatory status of Sildena in major regions like the EU or US?

Sildena, which contains the active ingredient sildenafil, is a fully authorized prescription medicine in both the US (FDA) and the EU (EMA). It is approved for treating both its Erectile Dysfunction and Pulmonary Arterial Hypertension indications under standard regulatory oversight.


Q: Do any official documents mention Sildena being linked to hearing changes?

Official documents list sudden decrease or loss of hearing as a serious adverse reaction that has been documented in post-marketing reports. Individuals who experience this effect are advised to seek medical attention immediately.


Q: If a person feels dizzy after taking Sildena, is that a sign of a serious issue?

Dizziness is listed as a common adverse effect in official documents. However, if dizziness is severe or accompanied by other symptoms like those of severe hypotension or cardiovascular events, it is documented as a situation where seeking prompt medical attention may be necessary.


Q: Is there a different set of safety guidelines for people with diabetes using Sildena?

Patients with diabetes were included in the clinical trials that established the drug's safety profile, but the general safety guidelines and contraindications are applied to all users. No specific additional set of guidelines unique to people with diabetes is published in the primary regulatory documents.


Q: What did the main clinical trials for Sildena focus on?

The main clinical trials focused on two primary areas: measuring the drug's efficacy (how well it achieved the intended result, such as global improvement or walk distance) and assessing its overall safety profile (documented adverse events) compared to a placebo over defined periods for its approved indications.


Q: Why is Sildena sometimes prescribed under a different name?

Sildenafil is available under different brand names which are used to distinguish between the approved uses (Erectile Dysfunction vs. Pulmonary Arterial Hypertension) and the available dosage strengths. The generic version is also marketed under the active ingredient name, sildenafil.


Q: Are there any special warnings for men who have anatomical differences using Sildena?

Official safety warnings advise caution for men who have a physical deformity of the penis (such as angulation or Peyronie's disease). Caution is also noted for those with conditions that may predispose them to priapism, which is a prolonged and potentially harmful erection.


Q: Is Sildena recommended for people who have had a stroke or mini-stroke?

Sildena is formally contraindicated in patients who have suffered a stroke or myocardial infarction (heart attack) within the last six months.


Q: What is the official advice on when to seek immediate medical attention after taking Sildena?

Official warnings describe situations where seeking immediate medical attention is necessary for several serious adverse reactions. These include priapism (an erection lasting longer than four hours), sudden decrease or loss of vision, or sudden decrease or loss of hearing.


Q: Does Sildena have a high potential for misuse or abuse?

The medicine is not classified as a controlled substance in major regulatory regions. While official documents do not focus on misuse potential, they refer to the drug's safety profile and note that non-medical use has been documented in post-marketing reports.


Q: Can someone take Sildena more than once in a 24-hour period?

The maximum frequency is dependent on the approved use. For the intermittent, as-needed regimen, the maximum frequency is once per day. For the continuous, scheduled regimen (used for PAH), the dosage is typically given three times per day.


Q: Does Sildena need to be taken consistently over time to work, or is it for single use?

Sildena is officially approved for use in two distinct patterns, depending on the condition. It can be taken as an intermittent, as-needed regimen (single use) for Erectile Dysfunction or as a continuous, three-times-daily regimen (consistent use) for Pulmonary Arterial Hypertension.

How should Sildena be stored and disposed of?

How to Store and Dispose of Sildena?

Strict adherence to official storage and disposal requirements ensures product integrity and safety.

Storage Requirements

Condition Requirement
Temperature Store oral tablets at controlled room temperature, typically 20 C to 30 C (68 F to 86 F). Store the reconstituted oral suspension at or below 30 C (86 F).
Handling Keep the medication in the original, tightly closed container and protect from light and moisture. Do not freeze or heat.
Stability The reconstituted oral suspension is stable and must be used within 60 days of preparation.
Safety Keep the medicine out of reach of children, ideally in a locked or inaccessible area.

️ Disposal Instructions

To dispose of unused or expired sildenafil, utilize a drug take-back program or mail-back envelope. If these options are unavailable, mix the drug with an undesirable substance (e.g., dirt, used coffee grounds), place the mixture in a sealed container, and discard it in the household trash. Do not flush sildenafil down the toilet.

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

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