antiarrhythmic drug

NOUN
19 LETTERS · STARTS WITH A

antiarrhythmic drug is a valid 19-letter word worth 33 points in Scrabble and 35 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
A1N1T1I1A1R1R1H4Y4T1H4M3I1C3D2R1U1G2
1 + 1 + 1 + 1 + 1 + 1 + 1 + 4 + 4 + 1 + 4 + 3 + 1 + 3 + 0 + 2 + 1 + 1 + 2 =33 PTS
DOUBLE WORD → 66TRIPLE WORD → 99
MEANING

What does antiarrhythmic drug mean?