I've turned in several reports, all answered essentially 'sorry for your difficulty'
The main problem with this quest is that the quest is given only after getting the 'effective cough medicine' quest from another NPC , if you don't have her quest, you can't get his quest. If you drop it, you no longer have her quest (you turned it in already!) so he won't talk to you to get it back.
From Runesdatabase, the only guest he gives after that is a daily for doing the same thing (scortch grass and venom), and he is a turn in for another quest from the giant mutated frog leg behind sardo castle.
The solution would be to toggle her quest back to incomplete, because he is working fine.
The quest you get from her sends you to him to get medicine, he sends you out to get the ingredients to make the medicine yourself.
Top link is Aliyah milfen's 'opener' for amden, second is amdens quest so you can finish hers, third is the daily he gives. 4th, is the quest Aliyah gives that is required to finish a title.
without her quest, you can't get the opener, if you drop the opener, you no longer have her quest so he can't give you the opener and that loop is closed.
http://www.runesdatabase.com/quest/4...cough-medicine
http://www.runesdatabase.com/quest/4...en%27s-request
http://www.runesdatabase.com/quest/4...-vermin-potion
http://www.runesdatabase.com/quest/4...weapon-advance
You can't get Amden's quest without having hers in your log, you can't complete hers without finishing his and getting the cough medicine. So she has to be reset in order to get any from him.
Edit: most of this was posted in the 'quest related bugs section:
http://forum.us.runesofmagic.com/showthr…2562#post492562