Erectile dysfunction (ED) is commonly treated with Cialis® (tadalafil) or Viagra® (sildenafil), which belong to a class of drugs called PDE5 inhibitors. These medications improve blood flow to the penis, helping men achieve and sustain erections. But what happens when they don’t work well enough or stop working altogether? For many men, the next option is Apomorphine—a unique treatment that works in the brain rather than the blood vessels.
How Apomorphine Works
- PDE5 inhibitors (Cialis/Viagra): Work peripherally by improving penile blood flow.
- Apomorphine: Works centrally by stimulating dopamine receptors in the brain that trigger sexual arousal and initiate erections.
This brain-based action makes Apomorphine especially useful for men whose ED is not primarily vascular in nature.
Recommended Dosing of Apomorphine
- Starting dose: 2 mg sublingual (under the tongue).
- If ineffective: May be increased to 3 mg, then 4 mg, and up to 5 mg.
- Maintenance dose: Most men achieve benefit at 3–4 mg per dose.
- Onset of action: Works within 15–20 minutes.
- Maximum frequency: Do not use more than once every 8 hours or more than 3 doses per day.
Comparison: PDE5 Inhibitors vs Apomorphine
| Feature | PDE5 Inhibitors (Cialis/Viagra) | Apomorphine (Sublingual) |
| Mechanism of Action | Boosts nitric oxide pathway → increases penile blood flow | Stimulates dopamine receptors in the brain → initiates arousal & erections |
| Site of Action | Penis / vascular tissue | Central nervous system (brain) |
| Onset of Action | 30–60 minutes (Viagra), 30–45 min (Cialis) | 15–20 minutes |
| Duration | Viagra: 4–6 hrs, Cialis: up to 36 hrs | Shorter acting (approx. 1–2 hrs) |
| Starting Dose | Viagra: 25–50 mg, Cialis: 5–10 mg | 2 mg sublingual |
| Maintenance Dose | Viagra: 50–100 mg, Cialis: 5–20 mg | 3–4 mg sublingual |
| Maximum Use | Once daily | Up to 3 doses per 24 hrs (≥8 hrs apart) |
| Best For | Vascular ED, first-line treatment | Non-responders to PDE5 inhibitors, neurologically influenced ED |