a few things...
tedalafil is available in USA by prescription only. Any other route is illegal. Sources that sell tedalafil without a rx are doing so against the law. In addition, there's a good chance you're not getting the proper product. Likely imported from India/China , unregulated.
the normally recommended daily dosage is 20mg .ANY change in dosage should be with close supervision of your physician. Tedalafil works by inhibiting PDE5. It affects PGE5 sites elsewhere in the body, not just the smooth muscle around dick. There are dangers with any drug, obviously dosage is important--stay within the therapeutic dose. If he's eyeballing it or just drinking directly from the bottle , um, not the best of ideas
if the chap is using tedalafil PLUS say a nitrite inhalant (ie., 'poppers') it can lead to very low blood pressure, dangerously low.