Dysgeusia (bitter, metallic taste) is the most common adverse reaction to Imovane.

It is generated from your GI tract, not your mouth. So drinking things to mask the taste or scraping your tongue with a scothbrite pad is not really that helpful. You shouldn't continue to scrape your tongue, you can cut your tongue which may lead to infection and further irritation.

One of the causes of Dysgeusia is Zinc deficiency. Ask your pharmacist about over the counter zinc lozenges. They have been shown to be the most effective treatment with the exception of stopping the medication.