A new clinical trial found that ketanserin, a blood pressure medication, could shorten the duration of an LSD trip in humans.

Ketanserin is a selective S2-receptor-blocking drug that’s normally prescribed to patients with hypertension to lower blood pressure.

In a recent study, researchers gave people LSD, followed by either ketanserin or placebo one hour later. Over the next 12 hours, they measured the LSD’s subjective effects on participants (hallucinations, sensory distortions, and other aspects of a psychedelic trip), as well as vital signs like heart rate and blood pressure, adverse effects, plasma brain-derived neurotrophic factor (BDNF) levels, and drug levels. They found that ketanserin reduced the duration of an LSD trip from an average of 8.5 hours to 3.5 hours.

Researchers already knew that ketanserin stops the hallucinogenic effects if administered before taking LSD. This study is significant because it demonstrates that ketanserin works if you give it to patients during the trip.

The study authors suggest ketanserin can be used as a “planned or rescue option to shorten and attenuate the LSD experience.” However, ketanserin took two hours to reduce the LSD trip significantly, so it should not be considered a quick fix.

Implications for Future Study of LSD

Anecdotally, many people report that experiences with LSD led to a positive effect on their well-being, similar to what people describe with psilocybin and ketamine. However, LSD hasn’t been studied much in a therapeutic context.

One reason for that is logistics. When a drug’s hallucinatory effects last 12 hours or more, it takes a lot of people-hours and expense to run human trials. Having a way to shorten the duration of LSD’s effects could make it easier to study in a clinical setting.

Ethical and Philosophical Considerations

Having a way out of a psychedelic experience raises ethical and philosophical questions about how psychedelic-assisted therapy should go.

  • Is the trip necessary for the therapeutic effect?
  • Is relinquishing total control part of the healing process, and would having medicine to regain control interfere with that?
  • Should therapists and clinicians “rescue” patients from the most challenging parts of the hallucination, when these scenarios could be the most transformative elements of therapy?
  • Who decides when it’s time to be done, patient or provider?
  • Or, should clinicians and therapists plan to use ketanserin to shorten the trip to last only a few hours as a matter of course, knowing that without intervention, a trip could 12 hours or more?

Everyone’s experience is different, so answers to these questions will probably vary depending on the circumstances. Nonetheless, they’re important to consider as we seek to understand LSD, other psychedelics, and the full picture of how these drugs produce their effects—not just the trip itself.