For most men, 100mg of Viagra is not too much: it is the highest dose on the label, and one tablet a day is within the recommended range. The usual starting dose of sildenafil is 50mg, taken about an hour before sex. Depending on how well it works and which side effects you get, it may be raised to a maximum of 100mg or lowered to 25mg (EMA). The dose becomes too much when you take a second tablet within 24 hours, go above 100mg, or have a condition or a medicine that rules sildenafil out.
What strengths of sildenafil are there in Australia?
Viagra is on the Australian Register of Therapeutic Goods in three strengths, 25mg, 50mg and 100mg (ARTG), and like every medicine for erectile dysfunction (ED) it needs a prescription here (healthdirect). Sildenafil is a PDE5 inhibitor: it relaxes the blood vessels in the penis so blood can flow in, and it does not cause an erection without sexual stimulation (healthdirect).
Does 100mg work better than 50mg?
For more men, yes. In the fixed-dose studies behind the European label, 82% of men taking 100mg said their erections improved, against 74% on 50mg, 62% on 25mg and 25% on placebo (EMA product information). That is why the label lets the dose go up to 100mg when 50mg is not enough, and why it stops there.
Is it safe to take more than 100mg?
No. Above 100mg you get more side effects, not a better erection: in volunteer studies, 200mg did not improve the effect but did make headache, flushing, dizziness, indigestion, a blocked nose and changes in vision more common; single doses up to 800mg caused the same side effects, more often and more severely (EMA product information). In practice, 100mg is the maximum safe dose of sildenafil per day: the label sets 100mg as the highest dose and once a day as the most often you should take it, and healthdirect says to take no more than one sildenafil tablet in 24 hours (healthdirect).
How long does one dose last?
Sildenafil usually starts working in 30 to 60 minutes, and its effects can last for up to 4 hours (healthdirect). A second 100mg of sildenafil later the same day is not a top-up but a second dose inside the 24 hours the label allows for one. If a tablet seems to fail, check the timing first: a heavy meal can slow it down (Viagra CMI).
Who should start lower than 100mg?
The label suggests considering a 25mg starting dose for men with severe kidney impairment or with liver impairment such as cirrhosis, because their bodies clear sildenafil more slowly; the dose can then be stepped up to 50mg and 100mg if needed. The same 25mg start is suggested for men taking medicines that slow the breakdown of sildenafil (CYP3A4 inhibitors, such as ketoconazole or erythromycin) and for men on an alpha-blocker, who should be stable on it first. With the HIV medicine ritonavir, taking sildenafil is not advised at all. Age alone does not call for a lower dose: no adjustment is needed at 65 and over (EMA product information).
Who should not take sildenafil at any dose?
Anyone who uses nitrates for angina, or a guanylate-cyclase stimulator such as riociguat. healthdirect also lists amyl nitrite and blood pressure medicines as interacting, with the risk of a sudden drop in blood pressure that is hard to treat (healthdirect). The label rules sildenafil out for men with severe liver disease, low blood pressure, a recent stroke or heart attack, an inherited eye disease such as retinitis pigmentosa, or past loss of vision from NAION (EMA). healthdirect adds that ED medicines are best avoided if sexual activity could put you at risk (healthdirect).
What side effects can 100mg cause?
The common ones are headache, facial flushing, a blocked nose and indigestion. Rarer but serious effects include changes in vision, sudden hearing loss, dizziness or fainting, an allergic reaction and priapism, an erection that will not go down (healthdirect). An erection lasting more than 4 hours needs the nearest hospital emergency department (healthdirect). If the common ones bother you at 100mg, the label allows stepping back to 50mg.
So is 100mg the right dose for you?
It can be, if your doctor prescribed it, 50mg was not enough and you take one tablet a day at most. It is the wrong dose if you use nitrates or riociguat, or if one of the conditions above applies to you.
