Assoc Prof Dr Ong Teng Aik      Consultant Urologist

Since 1998, the first-line therapy for ED consists of pills containing the phosphodiesterase-5 inhibitors (PDE5i). PDE5i improves blood flow to the penis. When a man anticipates or fantasizes about having sex, his brain is stimulated to send signals to his penis. With the aid of PDE5i, there is improved blood flow into the penis, allowing an erection to be achieved and maintained. After ejaculation, the penis will become soft again.

There are four main PDE5i medications, including sildenafil, vardenafil, tadalafil and udenafil. The half-life for sildenafil is about 4 hours so the effect will help the patient for about 12 hours. Vardenafil also lasts for about 12 hours. Tadalafil is the longest acting PDE5i – it has both the longest half-life (17 hours) and efficacy (36 hours). The choice of PDE5i depends on the individual’s needs. Some prefer short-acting PDE5i while others find the long-acting PDE5i more appropriate for their condition.

Leave the fatty food aside first

Fatty food affects the absorption of sildenafil and vardenafil. For example, sildenafil and vardenafil will not work so well after a meal of char kuey teow! So, stick to non-oily, low fat food for the ‘intimate’ dinners – it is also healthier this way. Incidentally, tadalafil is not affected by oily foods.

Just one pill a day?

The current practice of taking PDE5i is called ‘on demand’; which is to say, you only take PDE5i when you anticipate sexual activity within the next few hours.  It can be quite inconvenient for people who prefer spontaneity in their romantic encounters.

Now, there is a new concept – a daily dose of PDE5i. Studies show that taking low-dose tadalafil daily is effective and well-tolerated due to the long half-life of 17 hours. Another study shows that patients who were not satisfied with PDE5i on-demand were able to achieve normal erection by taking low-dose tadalafil once a day (OaD).

The 2015 European Association of Urology (EAU) guidelines say that this once a day tadalafil (or tadalafil OaD) is well tolerated and effective, and allows for spontaneous and frequent sexual activities.

In 2011, the US Food and Drug Administration approved tadalafil OaD for treating lower urinary tract symptoms (LUTS) – difficulty in passing urine, urinating frequently, waking up at night to pass urine. LUTS is caused by an enlarged prostate – a condition called benign prostatic hyperplasia (BPH).

When patients have prostate problems, they are either treated with medicine or surgery. If they don’t respond to medicine or have complications, they have to undergo surgery. There are two types of medicine available – alpha blockers (terazosin, doxazosin, alfuzosin and tamsulosin) to improve the urine flow and 5ARI (finasteride and dutasteride) to shrink the prostate.

A study has shown that tadalafil OaD allows patients with BPH to pass urine better and improves their sexual function as well. The 2015 EAU guidelines say tadalafil can be used on a daily basis to treat patients with both LUTS and BPH conditions. This is new information even for urologists.

The important thing is that tadalafil OaD keeps the flow going – just like the song River in you by Yiruma. So, you will have quality of life uninterrupted – that’s the concept of daily dose of PDE5I.

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