Why is This in the Patriot Act???

Apparently, congress is looking to pass their very own Sudafed bill. That would be pointless enough, but it gets better! The bill is attached to the Patriot Act renewal.

Lawmakers hope that federal restrictions — included in the agreement reached Thursday to reauthorize the USA Patriot Act — will stem a meth trade that has hit rural America particularly hard.

Why do we allow this kind of thing to happen? I mean honestly, why can't legislators be prevented from tacking on an amendment that has no relation to the rest of the bill? I'd also really like to know how much Sudafed it takes to make a typical dose of methamphetamine.