The Los Angeles rockers previously peaked at No. 2 with "Ghost" last October. That track followed Badflower's first entry on the chart, "Animal," which reached No. 28 in April 2017.
"Heroin" concurrently reaches a new No. 16 high on the Rock Airplay ranking, up 12% to 3.6 million impressions, according to Nielsen Music.
Badflower is the fourth act to tally a first career No. 1 on Mainstream Rock Songs in 2019, and the second in a row, following The Black Keys, whose "Lo/Hi" led the previous two weeks. Rival Sons and The Glorious Sons also led for the first time this year with "Do Your Worst" and "S.O.S. (Sawed Off Shotgun)," respectively. Comparatively, one act (Bad Wolves, with "Zombie") ruled for the first time in 2018, after three did so in 2017 (Greta Van Fleet, Nothing More and Ghost).
With Badflower's coronation, Mainstream Rock Songs boasts its highest number of newcomers to the top spot since 2015, when four such acts also ruled: Zac Brown Band, Red Sun Rising, Bring Me the Horizon and Royal Blood. This year (still essentially at its midpoint) and 2015 sport the highest totals for first-time No. 1 acts since 2013, when five reigned: Pop Evil, Young Guns, Halestorm, Device and Korn.
"Heroin" is the second single from Badflower's debut studio album, OK, I'm Sick, which debuted at No. 6 on the Hard Rock Albums tally dated March 9 with 7,000 equivalent album units earned.