Sildenafil vs Tadalafil: Comparing ED Medications in Australia

Erectile dysfunction (ED) affects roughly one in five Australian men over 40, and the number rises with age. Sildenafil and tadalafil are both phosphodiesterase type 5 (PDE5) inhibitors -- the first-line pharmacological treatment recommended by the Australian Therapeutic Guidelines (eTG). They work by the same mechanism (increasing blood flow to the penis during arousal) but differ in duration, timing, side-effect profile, and cost. This guide covers what matters when choosing between them.

How PDE5 Inhibitors Work

During sexual arousal, nitric oxide is released in the penile tissue, triggering production of cyclic GMP (cGMP). cGMP relaxes smooth muscle and increases blood flow, producing an erection. PDE5 is the enzyme that breaks down cGMP. By inhibiting PDE5, sildenafil and tadalafil allow cGMP to accumulate and sustain the erection for longer. Neither drug causes an erection on its own -- arousal is still required.

Quick Comparison Table

• Sildenafil: onset 30-60 minutes, duration 4-6 hours, take on demand, affected by fatty meals
• Tadalafil (as-needed): onset 30-60 minutes, duration up to 36 hours, less affected by food
• Tadalafil (daily low-dose 5mg): continuous effect, no timing required, also treats BPH symptoms

Sildenafil: The Original

Sildenafil was the first oral ED medication approved in Australia (1998). It is available as generic tablets in 25mg, 50mg, and 100mg doses. The typical starting dose is 50mg, taken approximately 30-60 minutes before sexual activity. It should not be taken more than once per day.

When sildenafil works well

• You prefer to take medication only when needed
• You can plan around the 30-60 minute onset window
• You want a shorter duration of action (some men prefer the drug to "wear off")
• Cost is a priority -- generic sildenafil is typically the cheapest PDE5 option

Key considerations

• High-fat meals can delay absorption by up to an hour and reduce peak effectiveness
• The 4-6 hour window means timing matters -- take it too early and the effect may fade
• Common side effects: headache (16%), flushing (10%), nasal congestion, visual disturbance (blue tinge, sensitivity to light)
• The visual side effects are unique to sildenafil among PDE5 inhibitors (it mildly inhibits PDE6 in the retina)

Tadalafil: The Long-Acting Option

Tadalafil was approved in Australia in 2003. It is available in 5mg, 10mg, and 20mg doses. The key differentiator is its 17.5-hour half-life -- roughly four times longer than sildenafil. This gives a window of action up to 36 hours, earning it the nickname "the weekend pill."

As-needed dosing (10mg or 20mg)

• Onset similar to sildenafil (30-60 minutes) but the window extends up to 36 hours
• Less affected by food -- can be taken with or without meals
• Some men prefer the flexibility of not needing to time the dose precisely
• Not to be taken more than once per day

Daily low-dose (5mg)

Tadalafil 5mg taken daily provides a continuous low level of PDE5 inhibition. After about 5 days of daily dosing, steady-state plasma levels are reached. This eliminates the need to plan around a dose -- spontaneity is fully preserved. Daily tadalafil is also TGA-approved for benign prostatic hyperplasia (BPH), so men with both ED and urinary symptoms may get a two-for-one benefit.

Key considerations

• Common side effects: headache (15%), dyspepsia/indigestion (10%), back pain, myalgia (muscle aches) -- these are more specific to tadalafil
• Back pain and muscle aches typically occur 12-24 hours after the dose and resolve within 48 hours
• No visual side effects (tadalafil does not inhibit PDE6)
• Daily dosing has a higher ongoing cost but may be preferred by men who are sexually active multiple times per week

PBS Status and Cost in Australia

Neither sildenafil nor tadalafil is listed on the PBS for erectile dysfunction. Both are private (non-PBS) prescriptions in Australia, meaning you pay the full price without government subsidy. However, because both are now available as generics, prices have dropped significantly.

• Sildenafil 50mg: $3-$8 per tablet (generic)
• Sildenafil 100mg: $4-$10 per tablet (generic)
• Tadalafil 20mg: $4-$10 per tablet (generic)
• Tadalafil 5mg daily: $1.50-$4 per tablet (generic), roughly $45-$120/month

Contraindications -- Who Should Not Take PDE5 Inhibitors

• Recent heart attack or stroke (within 6 months) -- discuss with your cardiologist
• Unstable angina or uncontrolled heart failure
• Severe liver impairment (lower doses required in moderate impairment)
• Severe renal impairment (dose adjustment needed)
• Hypotension (systolic BP below 90 mmHg)
• Alpha-blockers for prostate/BPH -- can cause postural hypotension; use with caution and start with the lowest PDE5 dose
• Retinitis pigmentosa (sildenafil) -- avoid due to PDE6 effect

Which One Should You Choose?

There is no universally "better" option. The choice depends on your lifestyle, how frequently you are sexually active, whether you have concurrent BPH, your side-effect tolerance, and cost preferences.

• You are sexually active once or twice a week and can plan timing
• You want the lowest per-dose cost
• You prefer a shorter duration of action
• Back pain or muscle aches are a concern (less common with sildenafil)

• You want a longer window without strict timing
• Spontaneity is important
• You eat at irregular times (tadalafil is less affected by food)
• Visual side effects are a concern (tadalafil does not cause them)

• You are sexually active 3+ times per week
• You also have BPH/urinary symptoms
• You want complete spontaneity with no planning required
• You are willing to take a daily medication

Switching Between Them

If one PDE5 inhibitor is not effective or causes unacceptable side effects, switching to the other is a standard clinical approach. Australian Therapeutic Guidelines recommend trying a PDE5 inhibitor on at least 4-6 separate occasions before concluding it is ineffective. The first attempt is often not representative -- anxiety, incorrect timing, or a heavy meal can affect results.

Getting a Prescription in Australia

Both sildenafil and tadalafil are Schedule 4 (prescription-only) medications in Australia. You need a prescription from an AHPRA-registered doctor. Telehealth consultations are appropriate for ED prescribing when the doctor can adequately assess your cardiovascular risk profile and medication history. InstantMed offers a structured ED assessment that covers the clinical information a prescribing doctor needs -- including a validated IIEF-5 questionnaire, cardiovascular history, and current medication review.