Rivotril is a brand name for Clonazepam, a sedative medication. While not a typical Spanish word, its inclusion in the lyrics is striking and immediately tells a story.
In the song, the artist mentions a "coctelito de mezcal y Rivotril pa' revivir" (a little cocktail of mezcal and Rivotril to revive). This line is a raw and honest depiction of self-medication and coping mechanisms, making the word memorable and indicative of the song's themes of struggle and escapism. It's a powerful, albeit dark, insight into the character's world.
The first line tells you how the day is going to go: "Amanecí con más ganas de beber que de vivir" ("I woke up with more desire to drink than to live"). Breakfast is "Desayuno un coctelito de mezcal" ("I have a little mezcal cocktail for breakfast") and "Y Rivotril pa' revivir" ("and Rivotril to bring me back to life"), and Carín León refuses to treat any of that as a problem. "Cada borracho tiene su manía" ("Every drunk has his own quirk"), he shrugs, "Y eso me funciona a mí" ("and that one works for me").
Then it stops being about him. "Si una mala mujer" / "Ha pasado por tu vida" ("If a bad woman has passed through your life"), you qualify too, and he hands you the membership card: "Compa, bienvenido al club" ("Buddy, welcome to the club"). He is specific about who else is in the room. "De borrachos que no olvidan" ("of drunks who don't forget"). "De los que lloran alcohol y no dejan de fumar" ("of the ones who cry alcohol and never stop smoking"). "De los que tenían buen corazón hasta que le fallaron" ("of the ones who had a good heart until someone let them down"). Behind all of it the band stays warm and unhurried, almost cheerful, and that distance between how the song sounds and what it is actually admitting is the best thing about it.