Apparent Non-Response to Phosphodiesterase Type 5 Inhibitors in Erectile Dysfunction: A Narrative Review of...

Background and Objectives: Apparent non-response to phosphodiesterase type 5 (PDE5) inhibitors is common, but the label conflates inadequate instruction or drug exposure, partial or absent response, treatment discontinuation, and coexisting clinical contributors. This narrative review presents an author-proposed structured reassessment framework, not a new or validated diagnostic classification. Materials and Methods: PubMed/MEDLINE was searched from database inception to 7 August 2026 using a documented, reproducible search strategy, with targeted checks of guideline, regulatory, clinical, observational, and mechanistic sources; selection was purposive, without a registered protocol, quantitative synthesis, or certainty-of-evidence grading. Results: PDE5 inhibitors preserve nitric oxide-cyclic guanosine monophosphate signaling but require sexual stimulation, adequate exposure, and sufficient erectile physiology. In one specialist-referral cohort, 88 of 250 men (35.2%) responded after structured re-education, being 88 of the 115 (76.5%) who accepted it, which should not be generalized. The framework separates trial and exposure adequacy, observed response documented with validated measures where feasible, targeted evaluation of contributing domains, and shared selection of oral optimization or an established non-oral option. Persistent clinically meaningful oral-PDE5-inhibitor non-response is defined by principle rather than by a fixed number of attempts, agents, or mandatory daily tadalafil. Conclusions: Structured reassessment may clarify why an observed response is inadequate and may support preference-sensitive management; whether it does so better than existing guidance has not been tested. Switching agents or daily tadalafil is not a prerequisite and should not delay vacuum therapy, intracavernosal injection, or penile-prosthesis discussion.