Total daily mg is 200 (100 mg twice daily) 200 mg x 20 days = 4,000 mg over 20 days. If the medication is only available in 20 mg tablets, divide 4,000 mg by 20 mg.
4,000/20= 200 tablets
You could’ve also calculated daily tablets and multiplied by number of days. 200 mg a day divided by 20 mg tablets = 10 tablets daily. Times 20 days equals 200 tablets.