Tadalafil

Evidence Level: L5

Predicted Indications: 10

Tadalafil
Tadalafil: From Erectile Dysfunction and Pulmonary Hypertension to Ambras Type Hypertrichosis Universalis Congenita

## Pharmacist Assessment Report

Tadalafil: From Erectile Dysfunction and Pulmonary Hypertension to Ambras Type Hypertrichosis Universalis Congenita

One-Sentence Summary

Tadalafil is a PDE5 inhibitor originally used for erectile dysfunction, benign prostatic hyperplasia and pulmonary hypertension. The TxGNN model predicts it may be effective for Ambras type hypertrichosis universalis congenita, but this is a model prediction only, with 0 clinical trials and 0 publications supporting it. The prediction should be treated with great caution and is most likely a knowledge-graph artifact.

Quick Overview

Item	Content
Original Indication	Erectile dysfunction, benign prostatic hyperplasia, pulmonary hypertension, psychologic dyspareunia, premature ejaculation (the Singapore licence records contain no indication text)
Predicted New Indication	Ambras type hypertrichosis universalis congenita
TxGNN Prediction Score	99.98%
Evidence Level	L5
Singapore Market Status	✓ Marketed
Number of Registrations	20
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available from the data compiled for this report. Tadalafil is known to be a PDE5 inhibitor, which raises cGMP and causes vasodilation. This is the basis of its efficacy in erectile dysfunction and pulmonary hypertension.

A speculative link to hair disorders is that cGMP-mediated changes in perifollicular blood flow could affect hair growth, as is seen with other vasodilators such as minoxidil. However, Ambras syndrome is a rare congenital disorder with a genetic basis (chromosome 8q rearrangements affecting TRPS1 regulation). A PDE5 inhibitor is unlikely to be therapeutically relevant, and the high score probably reflects shared neighbours in the knowledge graph rather than a true therapeutic effect.

The other top predictions (hypertrichosis, isolated genetic hair shaft abnormality, familial isolated trichomegaly, hypotrichosis simplex of the scalp) form a "hair-phenotype cluster". For several of these, such as hypertrichosis and trichomegaly, increased hair growth is the disease itself, so the direction of any effect is unclear.

The most biologically plausible of the ten predictions is kyphoscoliotic heart disease (score 99.43%). Kyphoscoliosis can cause chronic hypoxia and secondary pulmonary hypertension, and tadalafil is used in pulmonary hypertension. This remains a hypothesis, because PDE5 inhibitors can worsen ventilation-perfusion matching in hypoxic lung disease and no studies in this population were available.

Clinical Trial Evidence

Currently no related clinical trials registered for the predicted indication.

Literature Evidence

Currently no related literature available for the predicted indication.

For context, the only tadalafil-specific publication found among the lower-ranked predictions is a safety signal rather than support for efficacy:

PMID	Year	Type	Journal	Key Findings
17059442	2006	Case report	Cephalalgia	Tadalafil was associated with typical migraine aura without headache, suggesting it may trigger rather than treat aura (relevant to the migraine predictions, ranks 8-9)

Singapore Market Information

Twenty valid single-ingredient registrations exist. Five main authorizations are listed below. The licence records contain no approved indication text.

Authorization Number	Product Name	Dosage Form	Approved Indication
SIN12181P	CIALIS Tablet 20 mg (Lilly del Caribe)	Film-coated tablet	Not recorded
SIN13632P	CIALIS Tablet 5 mg (Lilly del Caribe)	Film-coated tablet	Not recorded
SIN16885P	Tadalafil-Teva FC Tablet 5 mg	Film-coated tablet	Not recorded
SIN15899P	Caliberi Orodispersible Film 5 mg (CTCBIO)	Soluble film	Not recorded
SIN16580P	Tadilas Film-Coated Tablets 20 mg (Krka)	Film-coated tablet	Not recorded

Safety Considerations

Contraindication-related conditions (from the knowledge graph, not label text): liver failure, epilepsy, aortic stenosis and other aortic valve disease, hypotensive disorder, blood coagulation disease, acute coronary syndrome, myocardial infarction, stroke and cerebrovascular disorders, sickle cell anaemia and other haemoglobinopathies, plasma cell myeloma, leukaemia, priapism, Peyronie disease, hearing loss disorders, and hypertrophic cardiomyopathy.

Drug Interactions: 100 interactions were identified. Most of those listed are of Moderate severity, including aprepitant, dexamethasone, clarithromycin, cimetidine, miconazole, clotrimazole, and the SGLT2 inhibitors (canagliflozin, dapagliflozin, empagliflozin, ertugliflozin). Papaverine is Minor. Several others (e.g., metformin, omeprazole, morphine) are of unknown severity.

Additional signal: A case report links tadalafil with migraine aura, which is a safety concern for the migraine predictions.

Package insert warnings and contraindications were not available. Please refer to the package insert for full safety information.

Conclusion and Next Steps

Decision: Hold

Rationale: The prediction is supported only by a graph-based score. There are no trials or publications, and the proposed mechanism is weak for a genetic disorder. The same applies to the other nine predictions, none of which has efficacy evidence. The only available literature, the migraine aura case report, points toward harm rather than benefit.

To proceed, the following is needed:

Package insert warnings and contraindications from HSA
Mechanism of action data from DrugBank
Clarification of the direction of effect for the hair-related predictions (whether tadalafil would increase or decrease hair growth)
If any prediction is pursued, kyphoscoliotic heart disease is the most plausible candidate, and it would require preclinical or clinical data on PDE5 inhibition in hypoxic pulmonary hypertension
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.