How Does Tadalafil Work?
Key Takeaways
- Mechanism: PDE5 inhibitor → boosts nitric oxide → increases blood flow to penile tissue
- Who can use: Men with ED or PAH (with cardiovascular clearance)
- Absolute contraindications: Nitrate medications, recent heart attack/stroke, severe liver disease
- Onset: 30 min-2 hours | Duration: Up to 36 hours
- Special caution: Patients with hypertension, kidney disease, or penile deformities
This comprehensive guide examines how tadalafil works for erectile dysfunction, detailing its unique mechanism of action as a PDE5 inhibitor that enhances blood flow to the penis. We'll explore tadalafil's extended duration of effectiveness (up to 36 hours), explain why it's often called the "weekend pill", compare it to other ED medications, and reveal what patients can realistically expect from this treatment.
How Tadalafil Works: Physiological Mechanism
Tadalafil enhances the natural erection process by increasing blood flow
Step 1: PDE5 Inhibition
- Blocks phosphodiesterase-5 (PDE5) enzyme in penile tissue
- Prevents breakdown of cyclic GMP (key vasodilator)
Step 2: Enhanced Nitric Oxide Effect
- Nitric oxide (released during sexual arousal) activates guanylate cyclase
- Increased cyclic GMP → smooth muscle relaxation in penile arteries
Step 3: Improved Blood Flow
- Blood vessels dilate → 200% increased flow to corpus cavernosum
- Enables erection with sexual stimulation (not spontaneous)
FAQs
Why can't I take tadalafil with nitrates?
The combination causes dangerous blood pressure drops:
- Nitrates increase cyclic GMP (like tadalafil)
- Synergistic effect → BP may crash to <70/40mmHg
- Risk persists for 48+ hours after last tadalafil dose
Even sublingual nitroglycerin (GTN spray) is prohibited.
 | Authored by Nabeel |
Medical Content Manager
Nabeel is a co-founder, and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
 | Reviewed by Dr. Waqas (GMC:7928708) |
Medical Doctor
Dr. Waqas is a GMC-registered doctor at Chemist Doctor, specialising in general health. He balances clinical precision with cultural sensitivity.
 | Approved by Usman |
Medical Director
Usman is a co-founder, and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 12 August 2025
Next Review: 14 February 2026
Published on: 11 August 2025
Last Updated: 12 August 2025
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