Comic Westerns are difficult to sustain. (Only "Maverick" had any success with it -- and that was because most of the stories were more or less serious, with deft comic touches.) It appears that, by the beginning of the second season, "Lardeo"'s writers were running out of ideas, and borrowed one from "Bewitched" (which had already run it into the ground).
Many "Bewitched" episodes revolve around a magic spell or potion that never works the way it's supposed to, producing odd or embarrassing side effects. In "A Double Shot of Nepenthe" (look it up!), it's a drug with the amazing ability to almost instantly destroy someone's will, making them the unwilling (and seemingly unknowing) servant of whoever administered the drug.
The problem is that it's fundamentally unbelievable. The closest real drugs approach this are so-called "truth serums", which relax a person to the point they become susceptible to suggestion. When the drug wears off, so does the suggestibility. The same is true of post-hypnotic suggestions, which vanish after the person goes to sleep.
The results in this episode are likely to make the viewer squirm, especially at the beginning, when a man -- after a single injection -- is told to push his best friend off a cliff. And he does so. He is then shot to death, so there won't be any witnesses. One doesn't expect even a comic Western to be free of violence. But I doubt "Laredo" had many on-screen murders.
The best stories are built around plausible character interactions. This one is not.