DOSEGUY

L-Tetrahydropalmatine

weak data

Also seen as: L-THP

The Dose Guy’s verdict
Sep 1, 2026
3 sources

L-tetrahydropalmatine has more human data than most of this shelf, and the mechanism is well understood. The catch: it’s a dopamine antagonist, which makes it a sedative and analgesic, not a cognitive enhancer. The heroin-withdrawal trial is genuinely interesting, and the poisoning literature says nobody died in 37 cases, though 10.8% needed mechanical ventilation and intensive care. If you want focus, this is the wrong compound, and semax or noopept are better starting points for that. If you want calm backed by real pharmacology, it’s one of the few here with actual receipts.

Would I take it?For calm, not clarity. Know what you're picking up.

What it is

L-tetrahydropalmatine, usually shortened to L-THP, is an isoquinoline alkaloid from Corydalis and Stephania plants, used in traditional Chinese medicine for centuries as a sedative and pain reliever. The pharmacology explains the old uses cleanly: it agonizes D1 dopamine receptors and antagonizes D2 receptors, a profile that produces sedation, analgesia, and reduced craving. It also blocks alpha4beta2 nicotinic acetylcholine receptors noncompetitively, which may be part of why it dulls stimulant reward.

This is not a nootropic in the usual sense. It sits on the cognition shelf because people looking for brain compounds will find it, and the honest answer is that it calms the brain rather than sharpening it. The clinical interest is in addiction and withdrawal, not focus.

What the research shows

The human data is real but small, pointed at addiction and pain rather than cognition:

In 120 heroin-dependent patients, four weeks of L-THP reduced somatic symptoms, mood symptoms, insomnia, and drug craving versus placebo. Among participants who remained after two weeks of medication, the three-month abstinence rate was 47.8% with L-THP versus 15.2% with placebo, p below 0.0005.Acta Pharmacol Sin 2008 · RCT · n=120
In 24 male cocaine users, oral L-THP at 30 mg twice daily for four days was safe and well tolerated during a cocaine challenge, with no meaningful difference in side effects versus placebo.J Clin Pharmacol 2017 · RCT · n=24
Among 37 acute rotundine poisoning cases, CNS depression predominated, 16.2% had QTc prolongation of at least 440 ms, 10.8% required mechanical ventilation, and no one died.Toxicol Rep 2026 · n=37
No randomized trial has tested L-THP for cognitive enhancement in healthy people.as of Aug 2026

Realistic protocols

People run L-THP for sleep, anxiety, and craving management. The dopamine-antagonist profile means the sedation is the mechanism itself. Dose-response is straightforward: more puts you down harder. Take it in the evening if you are using it for sleep. Stacking it with other sedatives or alcohol adds risk the poisoning data makes concrete.

Sleep/calm30–60 mgOral, evening. Start at 30 mg. Give it an hour before judging the weight.
Daytime calm30 mgA single low dose if you need it during the day. Expect sedation.
Ceiling60–120 mg/dayThe Western RCT tested 60 mg/day for four days safely. Chinese clinical use goes higher.

Side effects

The dopamine-antagonist profile means the side effects are the mechanism turned up too loud:

commonSedation, drowsiness, and slowed reaction time. This is the D2 blockade working. Do not drive on it until you know how hard it hits you.
monitorQTc prolongation appeared in 16.2% of overdose cases. If you have a cardiac history or take other QT-prolonging drugs, skip this one.
anecdotalFlat mood or emotional blunting with repeated use, consistent with dopamine antagonism. Some users report tolerance to the sedation within weeks.
unknownLong-term effects on dopamine receptor density from chronic low-dose use are unstudied. The D2-blockade profile raises the same questions any dopamine antagonist does.

Where to buy

Disguised Research–
$59.99 / unit
⚠ ⚠ Unreachable since Sep 11
✓ verified Sep 8
Read review →
Visit →

Prices move. Links are affiliate links; they never change a ranking, and scores are set before the deal exists.