Anything that was made to eat symbolizes “words” (truth or lies). For instance, bread symbolizes the word of God. Poison symbolizes evil lies which will cause spiritual death. Medication (in whatever form) symbolizes spiritual words or truth that is specifically prepared to help people get healed.
The pill that you saw was white, indicating or suggesting that it will have positive and good results if it is swallowed. This means that somebody prepared something (words) that appears to be the truth and good.
However, there are a few problems (symbols) that reveal two things: Only half of the “words” were given, the other half of the pill was held back. It was not cut with a knife (smooth), indicating that it was roughly sawn-off or broken off and there was no precision involved. The word of God is precise, like a sword that divides precisely (smooth edges). A pill, unless it is medication, is just a chemical and not proper food like milk (primary word of God) bread (solid word of God), or meat (solid word of God). So half of the words were given, what about the other half? Is it true or good? Is it really the same substance?
The other negative symbol was the darkness in the scene which either speaks of some demonic influences or bad circumstances involved in some way.