Sildenafil is a PDE5 inhibitor used in FDA-approved products for pulmonary arterial hypertension, or PAH, specifically within the WHO Group I pulmonary arterial hypertension context. Current REVATIO labeling describes benefits in exercise ability and clinical worsening in adults and includes a pediatric PAH indication for patients 1 to 17 years old.
The PAH use is supported by randomized clinical studies rather than by mechanism alone. In the pivotal SUPER-1 trial, sildenafil produced placebo-corrected improvements of approximately 45 to 50 meters in 6-minute walk distance across the studied dose groups after 12 weeks.
The active drug is the same sildenafil molecule used in erectile-dysfunction products, but the PAH context has different products, formulations, scheduled regimens, clinical endpoints and safety considerations. This page provides an indication-specific overview rather than individualized PAH treatment advice.
Sildenafil is an established PDE5 inhibitor within the treatment framework for WHO Group I pulmonary arterial hypertension. Current REVATIO labeling indicates sildenafil in adults to improve exercise ability and delay clinical worsening.
Evidence for that indication includes SUPER-1, a randomized double-blind placebo-controlled trial of 277 patients with PAH. At Week 12, placebo-corrected mean increases in 6-minute walk distance were approximately 45 to 50 meters across the sildenafil dose groups, with no additional short-term exercise benefit demonstrated for the higher studied doses compared with 20 mg three times daily.
A second important study, PACES-1, evaluated sildenafil added to stable intravenous epoprostenol. The adjusted treatment difference in 6-minute walk distance at Week 16 was approximately 26 meters, and clinical worsening occurred in 8 of 134 sildenafil-treated patients compared with 23 of 131 placebo-treated patients.
| PAH Evidence | Key Finding |
|---|---|
| SUPER-1 | 277 patients with PAH in a randomized placebo-controlled study |
| SUPER-1 exercise endpoint | Placebo-corrected improvement of approximately 45–50 m in 6-minute walk distance at Week 12 |
| PACES-1 | 267 patients receiving background intravenous epoprostenol |
| PACES-1 exercise endpoint | Adjusted treatment difference approximately +26 m at Week 16 |
| PACES-1 clinical worsening | 8/134 with sildenafil vs 23/131 with placebo |
Pulmonary hypertension is a broad clinical category, whereas pulmonary arterial hypertension is a specific pulmonary vascular disease group. Sildenafil's PAH indication belongs to WHO Group I rather than to pulmonary hypertension of every cause.
PAH involves increased resistance within the pulmonary arterial circulation and can progressively affect right-heart workload and functional capacity. Clinical evaluation therefore requires determining the underlying pulmonary-hypertension classification rather than relying on elevated pulmonary pressure alone.
This distinction matters for sildenafil because evidence and regulatory approval in PAH should not be generalized automatically to pulmonary hypertension caused by left-heart disease, lung disease, chronic thromboembolic disease or other non-PAH mechanisms.
| Term | Meaning |
|---|---|
| Pulmonary hypertension | Broad category of disorders associated with elevated pressure in the pulmonary circulation. |
| Pulmonary arterial hypertension | Specific pulmonary vascular disease classified as WHO Group I. |
| Sildenafil PAH indication | Applies within the product-specific WHO Group I PAH context. |
| Other pulmonary hypertension | Should not automatically be treated as equivalent to PAH. |
Current REVATIO labeling indicates sildenafil for WHO Group I PAH in adults to improve exercise ability and delay clinical worsening. It also includes pediatric patients 1 to 17 years old to improve exercise ability and, in children too young for standardized exercise testing, pulmonary hemodynamics thought to underlie improvement.
Not every sildenafil-containing PAH product has identical labeling. LIQREV, a 10 mg/mL sildenafil oral suspension approved under its own NDA, is labeled for PAH in adults, while current REVATIO labeling includes both adults and pediatric patients.
Generic sildenafil products can also differ in the exact labeling information they carry because product-specific regulatory circumstances can affect which indication or pediatric information appears. For the high-level indication map, see the sildenafil uses page.
| Product Context | Current PAH Label Context |
|---|---|
| REVATIO — adults | WHO Group I PAH; improve exercise ability and delay clinical worsening |
| REVATIO — pediatric patients 1–17 years | WHO Group I PAH; exercise ability or relevant pulmonary hemodynamics |
| LIQREV | WHO Group I PAH in adults |
| Generic sildenafil PAH products | Interpret according to the specific approved product labeling |
Sildenafil inhibits phosphodiesterase type 5, or PDE5, an enzyme responsible for degradation of cyclic guanosine monophosphate, or cGMP. PDE5 is present within pulmonary vascular smooth muscle, making this pathway directly relevant to PAH pharmacology.
By inhibiting PDE5, sildenafil increases cGMP availability within pulmonary vascular smooth-muscle cells. Increased cGMP promotes smooth-muscle relaxation and can produce vasodilation within the pulmonary vascular bed.
The drug also has systemic vasodilatory effects, although the therapeutic PAH context centers on pulmonary vascular signaling. The broader mechanism is covered on the how sildenafil works page.
| Mechanism Component | PAH Role |
|---|---|
| PDE5 | Enzyme that degrades cGMP |
| Sildenafil | Inhibits PDE5 |
| cGMP | Accumulates to a greater degree when PDE5-mediated degradation is reduced |
| Pulmonary vascular smooth muscle | Relaxes in response to increased cGMP signaling |
| Physiological consequence | Pulmonary vascular vasodilation |
The same PDE5 target can have different clinical significance depending on the physiological system in which it is being used therapeutically. In PAH, the relevant target environment is pulmonary vascular smooth muscle.
Reducing pulmonary vascular resistance can influence pulmonary hemodynamics and functional exercise capacity. This is why PAH trials use endpoints such as 6-minute walk distance, pulmonary arterial pressure, functional class and clinical worsening rather than erectile-function endpoints.
Sildenafil's PAH mechanism therefore cannot be understood only by transferring the familiar erectile-dysfunction narrative to the pulmonary circulation. The molecular target is shared, but the clinical endpoints and disease physiology are different.
| Level | PAH Interpretation |
|---|---|
| Molecular target | PDE5 |
| Signaling system | cGMP-related vascular signaling |
| Target tissue context | Pulmonary vascular smooth muscle |
| Functional endpoint | Measures such as 6-minute walk distance |
| Disease endpoint | Clinical worsening and PAH progression |
The sildenafil molecule used for PAH is the same active drug used in erectile-dysfunction products. The difference lies in the indication, product, strength framework, formulation and scheduled treatment model rather than in the identity of the active moiety.
ED labeling generally describes as-needed administration around sexual activity. PAH sildenafil is instead used within scheduled repeated-administration regimens designed for chronic pulmonary vascular treatment.
This distinction is regulatory and clinical, not merely semantic. A product labeled for one sildenafil indication should not be interpreted by copying the dosage or administration assumptions of another indication.
| Level | ED Context | PAH Context |
|---|---|---|
| Active ingredient | Sildenafil | Sildenafil |
| Drug class | PDE5 inhibitor | PDE5 inhibitor |
| Clinical indication | Erectile dysfunction | Pulmonary arterial hypertension |
| Treatment pattern | Generally as needed | Scheduled repeated administration |
| Product label | ED-specific | PAH-specific |
REVATIO is the major branded sildenafil product associated with the U.S. PAH regulatory framework. Current labeling includes tablets, powder for oral suspension and intravenous injection.
REVATIO is indicated for adults with WHO Group I PAH and also for pediatric patients 1 to 17 years old. The pediatric indication was added later in the product's regulatory history and should not be inferred from older versions of the label.
REVATIO is not a chemically different active drug from sildenafil used elsewhere; it is a product-specific regulatory framework. Brand history and product relationships are covered on the sildenafil and Revatio page.
| REVATIO Feature | Current Context |
|---|---|
| Active drug | Sildenafil |
| Adult indication | WHO Group I PAH |
| Pediatric indication | WHO Group I PAH in patients 1–17 years old |
| Oral tablet | 20 mg |
| Oral suspension | 10 mg/mL after reconstitution |
| Injection | 10 mg/12.5 mL single-dose vial |
The current U.S. PAH sildenafil landscape includes tablets, oral suspensions and an intravenous formulation. These dosage forms are not interchangeable descriptions of the same pharmaceutical product even though they contain sildenafil.
REVATIO includes 20 mg tablets, a powder reconstituted to a 10 mg/mL oral suspension and an intravenous injection containing 10 mg in 12.5 mL. LIQREV is a separate 10 mg/mL sildenafil oral-suspension product with its own NDA and adult PAH labeling.
Generic sildenafil PAH tablets and oral-suspension products are also available under their own approved labeling. The broader pharmaceutical comparison remains on the sildenafil formulations page.
| PAH Formulation Context | Current Example |
|---|---|
| Tablet | REVATIO and generic sildenafil 20 mg tablets |
| Powder for oral suspension | REVATIO, reconstituted to 10 mg/mL |
| Oral suspension | LIQREV 10 mg/mL and other applicable sildenafil products |
| Injection | REVATIO intravenous formulation, 10 mg/12.5 mL |
Oral sildenafil requires gastrointestinal administration and systemic absorption, while intravenous sildenafil bypasses gastrointestinal absorption and enters the systemic circulation directly.
Current REVATIO labeling uses the intravenous formulation in an adult PAH context and identifies a 10 mg intravenous dose as producing a predicted pharmacological effect of sildenafil plus its N-desmethyl metabolite equivalent to a 20 mg oral dose.
That equivalence is formulation-specific pharmacological information rather than a general rule for converting sildenafil doses. Injectable sildenafil is not an erectile-dysfunction route alternative. The detailed comparison remains on the oral vs injectable sildenafil page.
| Route Feature | Oral | Intravenous |
|---|---|---|
| GI absorption | Required | Bypassed |
| REVATIO formulation | Tablet or suspension | Injection |
| Current adult PAH label framework | Scheduled oral administration | Scheduled IV administration |
| Label pharmacological comparison | 20 mg oral reference | 10 mg IV predicted to provide equivalent pharmacological effect |
PAH changes the clinical purpose of sildenafil but does not replace its underlying pharmacokinetics. Once sildenafil reaches systemic circulation, distribution, CYP-mediated metabolism and clearance continue to determine circulating exposure.
Sildenafil is metabolized predominantly through CYP3A4, with CYP2C9 providing a smaller contribution. This is clinically relevant in PAH because strong CYP3A inhibitors can substantially increase exposure, while CYP3A inducers can reduce sildenafil concentrations.
Route also matters: oral products are affected by absorption and bioavailability, whereas intravenous sildenafil bypasses those presystemic steps. The technical ADME framework remains on the sildenafil pharmacokinetics page.
| PK Process | PAH Relevance |
|---|---|
| Absorption | Relevant to oral tablets and suspension |
| Bioavailability | Influences oral systemic input |
| Distribution | Occurs after systemic entry regardless of indication |
| CYP3A4 metabolism | Major pathway and source of important drug interactions |
| Clearance | Determines systemic exposure and concentration decline |
The most visible difference between ED and PAH sildenafil is the treatment schedule. ED products are generally used as needed, whereas current PAH labeling uses repeated scheduled administration throughout the day.
Current REVATIO adult labeling uses 20 mg orally three times daily as the recommended starting PAH regimen and permits product-specific titration under the current label. Pediatric oral dosing is weight-based. REVATIO injection has its own adult intravenous schedule.
Those label facts are included here only to demonstrate why PAH cannot be interpreted through ED timing conventions. They are not instructions for an individual treatment plan, and other sildenafil PAH products such as LIQREV have their own product-specific dosage labeling.
| Concept | ED Context | PAH Context |
|---|---|---|
| Treatment pattern | Generally as needed | Scheduled repeated administration |
| Adult REVATIO oral label | Not applicable | 20 mg three times daily as the recommended dosage |
| Pediatric PAH | Not applicable | REVATIO uses weight-based scheduled dosing |
| Intravenous sildenafil | Not an ED route | REVATIO has a specific adult PAH IV framework |
| Can ED timing rules be transferred? | No | No |
Current PAH sildenafil labeling contains the same three major formal contraindication categories seen across sildenafil products: concomitant organic nitrates, concomitant riociguat and known hypersensitivity to sildenafil or relevant product components.
PAH labeling also includes warnings that are especially important in the pulmonary vascular setting. Pulmonary vasodilators such as sildenafil can worsen pulmonary edema in pulmonary veno-occlusive disease, and current REVATIO labeling states that use in PVOD is not recommended.
Other PAH-label issues include hypotension, epistaxis, sudden vision or hearing loss, priapism and serious vaso-occlusive crises when sildenafil was studied in pulmonary hypertension secondary to sickle cell disease. Dedicated resources cover side effects, warnings, contraindications and drug interactions.
| Safety Category | Current PAH Label Context |
|---|---|
| Nitrates | Contraindicated |
| Riociguat | Contraindicated |
| Known hypersensitivity | Contraindicated |
| Pulmonary veno-occlusive disease | Use not recommended because pulmonary edema may occur |
| Hypotension | Vasodilatory effects require clinical consideration |
| Sudden vision or hearing loss | Requires prompt medical attention |
| Sickle-cell-associated pulmonary hypertension | Serious vaso-occlusive crises observed; PAH indication should not be generalized to this setting |
Organic nitrates and nitrites are formally contraindicated with sildenafil in PAH labeling. This restriction is not specific to erectile-dysfunction products and remains important when sildenafil is being used chronically for pulmonary arterial hypertension.
The interaction is pharmacodynamic. Nitric oxide donors increase cGMP signaling, while sildenafil inhibits PDE5-mediated cGMP degradation, creating the potential for excessive vasodilation and hypotension.
Because this is a formal contraindication rather than a minor interaction, the mechanism and regulatory context are covered in greater depth on the sildenafil and nitrates page.
| Component | Safety Context |
|---|---|
| Sildenafil | PDE5 inhibition |
| Organic nitrates / nitrites | Nitric-oxide-mediated cGMP signaling |
| Combined effect | Potentially excessive vasodilation and hypotension |
| Label classification | Contraindicated |
Riociguat is a soluble guanylate cyclase stimulator used in pulmonary-hypertension treatment contexts, making this interaction especially important on a PAH-focused sildenafil page.
Concomitant use of sildenafil with riociguat is contraindicated. The drugs act at different points of cGMP signaling but can produce overlapping vasodilatory and hypotensive effects.
This is not merely a theoretical pathway interaction: current sildenafil labeling specifically identifies riociguat as a contraindicated combination. The detailed mechanism remains on the sildenafil and riociguat page.
| Medicine | Pathway Context |
|---|---|
| Sildenafil | Inhibits PDE5-mediated cGMP degradation |
| Riociguat | Stimulates soluble guanylate cyclase |
| Combined effect | Can potentiate hypotensive effects |
| Label classification | Contraindicated |
PAH sildenafil has clinically important interactions beyond its formal contraindications. Current REVATIO labeling states that concomitant use with strong CYP3A inhibitors is not recommended because sildenafil exposure can rise substantially.
Enzyme induction can push exposure in the opposite direction. Bosentan and other CYP3A-inducing contexts can reduce sildenafil concentrations, making the interaction relevant to both pharmacokinetics and PAH treatment planning.
Current REVATIO labeling also advises patients not to combine REVATIO with VIAGRA or other PDE5 inhibitors because the safety and efficacy of overlapping PDE5-inhibitor therapy have not been established. The broader evidence framework remains on the sildenafil drug interactions page.
| Interaction Type | PAH Label Context |
|---|---|
| Strong CYP3A inhibitors | Concomitant use not recommended in current REVATIO labeling |
| CYP3A inducers | Can reduce sildenafil systemic exposure |
| Other PDE5 inhibitors / VIAGRA | Concomitant use should be avoided |
| Blood-pressure-lowering medicines | May increase hypotensive effects |
| Nitrates / riociguat | Formal contraindications |
Pulmonary arterial hypertension management involves more than identifying sildenafil as an approved medicine. Treatment depends on confirming the PAH classification, assessing disease severity and risk, considering other PAH therapies and evaluating the patient's broader clinical context.
Even label-based sildenafil information differs by product and population. Current REVATIO labeling contains adult and pediatric dosing frameworks and multiple dosage forms, while LIQREV is an adult oral-suspension product with its own labeling.
The trial data on this page therefore describe evidence supporting sildenafil's PAH role rather than identifying the appropriate treatment strategy for an individual patient.
| This Page Covers | This Page Does Not Provide |
|---|---|
| PAH indication and clinical evidence | Diagnosis of pulmonary hypertension subtype |
| Mechanism overview | Individual treatment selection |
| Product and formulation context | Personal dosing regimen |
| General label framework | Drug-combination strategy |
| Major safety categories | Patient-specific prescribing advice |
Sildenafil for PAH is best understood as an evidence-based, indication-specific use of PDE5 inhibition within WHO Group I pulmonary arterial hypertension. Randomized trials demonstrated improvements in exercise capacity, while additional studies support effects on clinical worsening in relevant PAH treatment settings.
The same active drug appears in ED products, but the PAH context uses different clinical endpoints, products, dosage forms and scheduled treatment frameworks. REVATIO additionally has current pediatric labeling for patients 1 to 17 years old.
A complete interpretation therefore connects four layers: the confirmed PAH indication, pulmonary vascular PDE5 mechanism, product-specific formulation and labeling, and the PAH-specific safety environment including PVOD, interacting vasodilators and CYP-mediated exposure changes.
| Question | Sildenafil PAH Answer |
|---|---|
| What PAH category is covered? | WHO Group I pulmonary arterial hypertension |
| Is efficacy supported by randomized trials? | Yes |
| What did SUPER-1 demonstrate? | Approximately 45–50 m placebo-corrected improvement in 6-minute walk distance at Week 12 |
| Does current REVATIO labeling include children? | Yes; pediatric patients 1–17 years old |
| What formulations exist in the PAH framework? | Tablets, oral suspensions and REVATIO injection |
| Is PAH sildenafil used like ED sildenafil? | No; the clinical and scheduled-treatment frameworks are different |
| What are the core formal contraindications? | Nitrates, riociguat and known hypersensitivity |
Current REVATIO labeling indicates sildenafil for WHO Group I pulmonary arterial hypertension in adults to improve exercise ability and delay clinical worsening. REVATIO also has a pediatric PAH indication for patients 1 to 17 years old.
In the randomized SUPER-1 trial, sildenafil produced placebo-corrected improvements of approximately 45 to 50 meters in 6-minute walk distance at Week 12. In PACES-1, sildenafil added to epoprostenol improved 6-minute walk distance and delayed clinical worsening compared with placebo.
Yes. The active ingredient is sildenafil in both settings, but PAH and ED use different product labels, treatment schedules, clinical endpoints and formulation contexts.
Current U.S. PAH products include sildenafil tablets and oral suspensions, while REVATIO also includes an intravenous injection. LIQREV is a separate 10 mg/mL oral-suspension product labeled for adult PAH.
No. Sildenafil's approved PAH indication is specific to WHO Group I pulmonary arterial hypertension. Pulmonary hypertension has multiple causes and classifications that should not automatically be treated as equivalent to PAH.
Major issues include contraindications with nitrates and riociguat, hypotension, strong CYP3A interactions, avoidance of overlapping PDE5 inhibitors, and PAH-specific warnings such as possible pulmonary edema in pulmonary veno-occlusive disease.