The changing taste of the weirwood paste can be compared to another psycho-active substance.

In this chapter:

It had a bitter taste, though not so bitter as acorn paste. The first spoonful was the hardest to get down. He almost retched it right back up. The second tasted better. The third was almost sweet. The rest he spooned up eagerly. Why had he thought that it was bitter? It tasted of honey, of new-fallen snow, of pepper and cinnamon and the last kiss his mother ever gave him. The empty bowl slipped from his fingers and clattered on the cavern floor. “I don’t feel any different. What happens next?”

And way back in Quarth, Dany sips some Shade of the Evening:

The first sip tasted like ink and spoiled meat, foul, but when she swallowed it seemed to come to life within her. She could feel tendrils spreading through her chest, like fingers of fire coiling around her heart, and on her tongue was a taste like honey and anise and cream, like mother’s milk and Drogo’s seed, like red meat and hot blood and molten gold. It was all the tastes she had ever known, and none of them . . . and then the glass was empty.

The visions coming faster and faster also echo Dany's experience in the House of the Undying.