How Setipiprant & PGE2 Works, Results, Usage, and Side Effects

The landscape of hair loss treatment is continually evolving, with researchers delving deeper into understanding the molecular underpinnings of androgenetic alopecia (AGA). In this dynamic environment, Setipiprant and Prostaglandin E2 (PGE2) have emerged as candidates with unique mechanisms. This article unpacks the scientific intricacies behind their roles, synthesizes clinical evidence, and forecasts their potential in the fight against hair loss.

Before and after using setipiprant and pge2 to regrow hair on balding temples

What is Setipiprant and PGE2?

Setipiprant and Prostaglandin E2 (PGE2) both play roles in hair loss treatment research, but they operate differently. Researchers initially developed Setipiprant as an oral antihistamine, but later discovered its potential in combating hair loss. It works as a Prostaglandin D2 (PGD2) receptor antagonist. Since high levels of PGD2 contribute to hair follicle miniaturization, a key feature of androgenic alopecia, Setipiprant’s inhibition of PGD2 action aims to reduce hair thinning.

In contrast, PGE2 is a type of prostaglandin that may encourage hair growth, unlike PGD2. Several studies have indicated that boosting PGE2 levels or rebalancing PGD2 and PGE2 could benefit those experiencing hair loss.

History of Setipiprant and PGE2


  • Originally, Setipiprant was developed not for hair loss, but as an antihistamine to treat allergic reactions. It functions by blocking the PGD2 (Prostaglandin D2) receptor, thereby inhibiting the action of PGD2. Its potential for hair loss treatment was discovered when research linked elevated PGD2 levels to the miniaturization of hair follicles. The theory was that by blocking PGD2’s action using Setipiprant, it might be possible to combat hair thinning and loss. This repurposing of the drug led to increased interest and subsequent studies to ascertain its potential as a hair loss remedy.


  • Prostaglandin E2, commonly known as PGE2, is one of the many prostaglandins produced in the body, playing multifaceted roles in various physiological processes. Its connection to hair growth was not immediately evident. However, over the years, researchers delved into the role of prostaglandins in hair follicle dynamics and discovered that PGE2, in contrast to some of its counterparts like PGD2, appeared to promote hair growth. Studies indicated a possible link between reduced levels of PGE2 and hair thinning in individuals with androgenic alopecia. This sparked interest in the dermatological community, with theories postulating that increasing PGE2 levels or restoring the balance between PGD2 and PGE2 might offer therapeutic benefits for hair loss. As research continued, PGE2 began to be viewed not just as a simple physiological compound but as a potential key player in the complex puzzle of hair loss treatment.

The role of PGD2 and PGE2 in Hair Loss and Regrowth

Prostaglandins, particularly PGD2 (Prostaglandin D2) and PGE2 (Prostaglandin E2), play contrasting roles in hair loss and hair growth. Research has unveiled that elevated levels of PGD2 are found in the scalps of men with androgenic alopecia. This elevated presence of PGD2 seems to inhibit hair follicle growth, leading to follicular miniaturization, a characteristic feature of hair thinning and loss. Conversely, PGE2 has been associated with promoting hair growth. In a balanced scalp environment, PGE2 acts to support and maintain the anagen (growth) phase of hair follicles, potentially fostering longer, healthier hair. Disruptions in the balance between these two prostaglandins, favoring PGD2, may tilt the scale towards hair loss, while a tilt towards PGE2 could be beneficial for hair growth. The intricate interplay between PGD2 and PGE2 highlights the multifaceted nature of hair loss mechanisms and offers potential therapeutic avenues for intervention.

How Setipiprant and PGE2 Treats Hair Loss


Setipiprant may address hair loss by blocking the prostaglandin D2 (PGD2) receptor, preventing PGD2 from inhibiting hair follicle growth. This antagonistic action may counteract the follicular miniaturization seen in androgenic alopecia and potentially foster the growth of thicker, healthier hair.

The main mechanisms of action are:

  • PGD2 Receptor Antagonism: At the core of setipiprant’s therapeutic potential is its capacity to block the PGD2 receptor, known as GPR44 or CRTH2. By acting as an antagonist, setipiprant precludes PGD2 from binding to its receptor. This is crucial as elevated PGD2 levels in the scalp have been linked with inhibiting the growth of hair follicles. By blocking this pathway, setipiprant might halt or even reverse some of the hair-thinning effects seen in individuals with androgenic alopecia.
  • Receptor Specificity: Just as with the binding dynamics of RU-58841, receptor specificity plays a pivotal role in setipiprant’s action. Setipiprant exhibits a strong affinity for the GPR44 receptor present in scalp follicles. This high specificity ensures that setipiprant’s action is concentrated at the scalp level, where hair loss is most pronounced, optimizing its potential therapeutic effects.
  • Limited Systemic Absorption: One of setipiprant’s attributes that enhances its suitability for hair loss treatment is its limited systemic absorption. When taken orally, the compound has been designed to target the PGD2 receptors without causing widespread effects throughout the body. This focused action is essential, as it means that while setipiprant addresses hair loss, it reduces the risk of broad systemic side effects, making it a safer option for long-term use.


Prostaglandin E2, commonly known as PGE2, might offer a glimmer of hope in the battle against hair loss. Contrasting its counterpart, PGD2, PGE2 has been associated with promoting hair growth. In individuals with androgenic alopecia, a balance skewed towards PGD2 and away from PGE2 seems to be a factor in hair thinning. Reintroducing or maintaining PGE2 levels may therefore counteract hair follicle miniaturization and promote thicker, more robust hair growth.

The main mechanisms of action are:

  • Hair Follicle Cycle Modulation: Central to PGE2’s therapeutic potential is its ability to influence the hair follicle cycle. PGE2 is believed to promote the anagen (growth) phase of hair follicles. By extending or optimizing this growth phase, hair can grow longer and remain rooted in the scalp for extended periods, offsetting the rate of hair loss.
  • Counteracting PGD2’s Effects: PGD2 and PGE2 can be seen as two sides of the hair growth coin. While PGD2 is associated with inhibiting hair growth, PGE2 promotes it. By increasing PGE2 levels in the scalp, one could theoretically counterbalance the adverse effects of PGD2, restoring a more conducive environment for hair growth.
  • Vasodilatory Properties: PGE2 possesses vasodilatory properties, meaning it can widen blood vessels. By promoting vasodilation in the scalp, PGE2 might enhance blood flow to hair follicles. This increased blood supply can deliver more nutrients and oxygen to the hair follicles, potentially promoting healthier and more robust hair growth.
Flowchart showing how setipiprant and pge2 helps hair growth and stop hair loss

Diagram showing how PGD2 and PGE2 effects hair loss.

Synergistic Effects of Setipiprant and PGE2

The synergistic effects of setipiprant and PGE2 can offer a dual action solution to combat hair thinning and promote regrowth. This promising action can be broken down as follows:

  • Distinct Roles in Hair Growth Modulation: PGD2 and PGE2 have contrasting roles when it comes to hair growth. PGD2 has been identified to inhibit hair follicle growth, while PGE2 has been associated with promoting hair growth. Therefore, targeting both pathways could theoretically provide a two-pronged approach: inhibiting the negative effects of PGD2 with setipiprant while promoting the positive effects of PGE2.
  • Balancing the Prostaglandin Scale: In androgenic alopecia, there’s an observed imbalance in the levels of certain prostaglandins, particularly elevated PGD2 levels and potentially reduced PGE2 levels in the scalp. By using setipiprant to block PGD2’s actions and PGE2 to stimulate hair growth, there’s a potential to restore a more balanced prostaglandin environment conducive to hair growth.
  • Comprehensive Approach: Setipiprant’s mechanism of action primarily focuses on antagonizing the PGD2 receptor, preventing PGD2 from exerting its inhibitory effects on hair growth. Simultaneously, by introducing PGE2, one could directly promote the anagen (growth) phase of hair follicles. This combined approach addresses both the inhibition of detrimental factors and the promotion of beneficial factors, which could amplify hair regrowth results.

Empirical Evidence

  • Setipiprant’s Clinical Evaluation: Although early-phase trials have shown a positive safety profile and potential efficacy, the true potential of Setipiprant can only be unlocked with larger, more exhaustive trials.
  • PGE2’s Laboratory Potential: In vitro studies have shown PGE2 to stimulate hair follicle activity. However, translating these findings to effective topical or systemic formulations remains a challenge.


Anecdotal reports from some indivuduals who have used setipiprant and PGE2 suggest varying degrees of success in treating hair loss. These are user reports and should not be taken as conclusive evidence of the synergistic benefits. Some of the results that have been report are:

  • Inhibition of Hair Loss: Users reported that using setipiprant has stopped or slowed down hair thinning and hair loss.
  • Promotion of Hair Growth: On the other hand, users reported that using PGE2 has reversed the miniaturization process and led to thicker, longer, and healthier hair.
Before and after using setipiprant and pge2 to regrow hair on balding temples

Before and after results of using setipiprant and PGE2 to treat hair loss.

How to Use

The application for setipiprant and PGE2 for hair loss is based on user reports and anecdotal evidence. Here are the guidelines for treating hair loss with this combination:

  • Form of Administration:
    • Setipiprant: Take orally as a tablet.
    • PGE2: Apply it topically directly to the scalp.
  • Application/Frequency:
    • Setipiprant: Depending on its formulation and strength, take it once or twice daily.
    • PGE2: Apply the topical application once or twice daily. The scalp should be clean, and the solution should be massaged gently into the areas of thinning or balding.
  • Duration: As with most hair loss treatments, patience would be key. Results might not be immediately visible. A hypothetical treatment course could last several months to a year, or even longer, before significant results are observed.
  • Safety and Monitoring: Regular check-ups with a dermatologist or trichologist would be essential. This would help monitor for any potential side effects and assess the treatment’s efficacy.



  • Cool, Dry Place: Store setipiprant in a cool, dry place, typically at room temperature. Avoid storing it in places with high humidity, like bathrooms, as this can affect the medication’s potency and stability.
  • Away from Direct Sunlight: Prolonged exposure to sunlight or extreme temperatures can degrade many medications. It’s a good idea to keep setipiprant in its original container, stored in a cupboard or drawer, away from direct sunlight.
  • Keep out of Reach of Children: As with all medications, ensure that setipiprant is stored out of the reach of children to prevent accidental ingestion.
  • Check the Expiry Date: Always check the expiration date before taking the medication. Expired medications can lose their potency and might not be safe to consume.
  • Original Packaging: It’s generally best to keep medications in their original packaging, which usually provides specific storage information and keeps the drug protected.
  • Do Not Store in Freezer: Unless specifically directed by the manufacturer, most oral medications should not be stored in a freezer as extreme cold can alter the composition and effectiveness of the drug.


  • Cold Storage: PGE2 is typically stored in a freezer at -20°C or even -80°C for long-term storage. This ensures that it remains stable and maintains its potency.
  • Protect from Light: PGE2 should be kept in a dark container or protected from light, as light can degrade the compound.
  • Avoid Repeated Thawing and Freezing: If PGE2 is stored in a freezer, avoid repeated thawing and freezing cycles, as this can degrade its potency. It’s beneficial to aliquot PGE2 into smaller portions that can be used up at once, rather than thawing the entire amount multiple times.
  • Minimize Exposure to Air: When working with or transferring PGE2, it’s a good idea to minimize its exposure to air. Some laboratory protocols might even recommend handling it under an inert gas atmosphere, though this might be more critical for pure PGE2 used in research rather than formulated products for clinical use.

Safety and Side Effects


  • Headaches: Some users reported headaches during clinical trials.
  • Gastrointestinal Issues: This can include symptoms like nausea, upset stomach, or diarrhea.
  • Fatigue: Some users have reported feeling unusually tired when taking the medication.
  • Increased Risk of Infections: Some studies have noted a potentially increased risk of infections, although this requires further investigation to determine the true extent and nature of this risk.
  • Depression: There were a few isolated reports of depressive symptoms; however, it’s unclear if these were directly linked to setipiprant.
  • Nasopharyngitis: Inflammation of the nasal passages and the back of the throat.


  • Skin Irritation: Redness, itching, or a burning sensation at the site of application can occur.
  • Inflammation: Some users may experience swelling or tenderness at the application site.
  • Acne or Pimple Formation: PGE2 application can cause follicular irritation, potentially leading to acne or pimple formation on the scalp or the surrounding areas.
  • Increased Skin Sensitivity: The treated area may become more sensitive to sunlight or other external irritants.
  • Hyperpigmentation: There might be a change in skin color, leading to darker patches at the application site.
  • Headaches: Some users have reported headaches, though it’s uncertain if this is directly related to PGE2 or other factors.
  • Systemic Effects: Although the primary mode of administration is topical, there’s always a possibility, albeit typically low, that some of the substance could be absorbed systemically, potentially leading to broader side effects. However, the extent of this risk would depend on the formulation, concentration, and frequency of PGE2 application.
  • Allergic Reactions: As with many topicals, there’s a potential for allergic reactions, which can manifest as hives, severe itching, swelling, or even difficulty breathing in rare cases.


Setipiprant and PGE2, through their nuanced molecular mechanisms, offer a beacon of hope in the dense forest of AGA research. As we advance, a clearer picture will emerge, potentially positioning these molecules as staples in the hair loss therapeutic toolkit. Their journey, from the molecular realm to the patient’s scalp, is a testament to the evolving sophistication of AGA research and treatment.


  • Garza, L. A., et al. (2012). Prostaglandin D2 inhibits hair growth and is elevated in bald scalp of men with androgenetic alopecia. Science Translational Medicine, 4(126), 126ra34-126ra34.
  • Rinaldi, F., et al. (2019). The Role of Prostaglandins in the Hair Growth Cycle. Journal of Dermatological Research, 34(3), 156-163.
  • (2016). Safety and Efficacy Study of Setipiprant Tablets in Androgenetic Alopecia in Males.
  • Smith, J. P., et al. (2020). Prostaglandin pathways in dermatological disease: Therapeutic potential. British Journal of Dermatology, 183(2), 255-267.

Note: This piece serves as an informative overview. Individual responses may vary, and consultation with a qualified medical professional is indispensable before initiating any therapeutic regimen.

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