The FDA recall on Hylands in 2010 was the result of infants who fell ill with symptoms consistent with belladonna toxicity. I'm not knowledgeable about homeopathics admittedly, but that's quite worrisome for me. It seems that in that case, the formulation was off and the medication was not merely the "essence" of belladonna. My concern is that there are no guarantees that a company would get the formulation right in the future either.
At any rate, the other suggestions are great. We're not teething yet over here, but I'd like to be prepared!