A generic version of a popular drug to treat erectile dysfunction is now available to Australian men, with a potential saving of nearly $200 a month.

A popular erectile dysfunction medication has just become more affordable for the 20 per cent of Australian men suffering from the condition.

The PDE5 inhibitor 'tadalafil' is now "off patent" making it cheaper, says Darren Katz, Andrology Special Advisory Group leader for the Urological Society of Australia and New Zealand.

"This will be a significant cost saving for many of our urological patients with erectile dysfunction, including those experiencing side effects from diabetes or prostate cancer treatment," Dr Katz said in a statement on Thursday.

Erectile dysfunction affects around one-in-five men in Australia.

Sold in Australia under the trade name Cialis, tadafil is one of a number of medications that help men with erectile dysfunction.

It's also used to treat the symptoms of benign prostatic hyperplasia (enlarged prostate), including difficulty with urination.

"It has not come cheap with men paying around $200 per month," Dr Katz said.

As of this week, the generic version will be around $20 to $30.

"We would hope the greater affordability of this drug will stop men wasting their money on unproven and potentially risky 'treatments' over the internet," Dr Katz said.

Not only do they not work, they also contain ingredients that can interact in a dangerous way with medications, including those for diabetes, high blood pressure, high cholesterol and heart disease - all conditions often associated with erectile dysfunction.

"While it's a sensitive topic we encourage all men with erectile dysfunction to consult a doctor," Dr Knox said.

Erectile dysfunction is usually a symptom of underlying psychological or physical issues or a combination of both so it's important any underlying conditions don't go undiagnosed.

There's emerging evidence that men with erectile dysfunction may also have heart disease, which puts them at risk of a heart attack.