Transmute Potion to Poison

Transmute Potion to Poison
School transmutation; Level alchemist 2
Casting Time: 1 standard action
Components: S
Range: personal
Target: you
Duration: 1 round then 1 minute/level; see text
This extract causes you to take on a pale, sickly pallor for 1
round. During this time, if you consume a potion, it has no
effect. Instead, your mouth fills with a vile poison that you can
spit onto a weapon as a free action. If you do not spit out the
poison in 1 round, it affects you instead. The effect of the poison
depends on the level of spell contained in the potion consumed
(see sidebar). If the poison is not used within 1 minute per caster
level it becomes inert. You can only create one dose of poison
in this way per casting of this spell.

How do you even use this extract?
Does the "1 round" duration mean you have to drink this extract, drink a second potion and spit it out in the current round. Or does the duration mean you can drink/spit the potion on your next turn.

Either way, it seems pretty stupid. I have to burn an extract slot and a random potion in order to poison my weapon. As an alchemist, I can already make as much poison as I want, and applying it to my weapons is a simple move action by lvl 3 or a swift action at lvl 6. (you can't get this extract until lvl 4).
Am I missing something?