Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain black tinted tongue after taking
pepto-bismol is not an abnormal finding and it is due to bismuth present in it..
Due to accumulation of particles over the tongue papillae there is discolouration over the tongue..
It is a commonly seen finding after taking chewable or liquid
pepto bismol and you need not to worry about it..
I would suggest you to start gargling with 1:1 solution of
hydrogen peroxide and water..
Clean the tongue with a tongue scraper..
Chew more of hard foods like carrots, apple etc.
Gradually the staining will subside..
If the discolouration does not start fading gradually consult an Oral Physician and get evaluated..
Hope this information helps..
Regards.