256 mg of phenobarbital taken with water on empty stomach (5rs out from a light meal) (3 x 64 mg pills) & (2 x 32 mg pills) I made sure to wait for the effects to start setting in before I cooked and ate a small cheese pizza, so as to ensure the drug made its way into the system unimpeded.
Phenobarbital
Well-documented
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 17 combo interactions documented
- toxicity data (PsychonautWiki, PubChem)
Well-documented
Multiple authoritative sources agree on dosing and effects.
- 4 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 17 combo interactions documented
- toxicity data (PsychonautWiki, PubChem)
Aliases: Pheno, Luminal, Solfoton, Phenobarb, Phenobarbitone
Summary
Phenobarbital is a long-acting barbiturate with extremely slow elimination and a narrow therapeutic window. It binds to a distinct allosteric site on GABA-A receptors separate from benzodiazepines, making combinations particularly dangerous as effects potentiate multiplicatively. Tolerance develops rapidly but not to lethal doses, narrowing the safety margin.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 50-100mg | 100-150mg | 150-300mg | 300mg+ |
Light
Common
Strong
Heavy
Sources
Oral
Dose ladder — dose.wiki, PsychonautWiki, TripSitOnset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset | Total |
|---|---|---|---|---|---|
| Oral | 15-60 min | 1-2 hrs | 4-6 hrs | 12-24 hrs | 17.25-33 hrs |
| Intravenous | 5 min | - | 15-30 min | 12-24 hrs | 12.33-24.58 hrs |
Tolerance
Build-up
develops over 1–4 weeks of daily use; hypnotic tolerance faster than anxiolytic tolerance
Reset
Falls after you stop, at a rate that varies from person to person. If you've been using regularly, cut down gradually with medical help rather than stopping suddenly.
No tolerance chart. Our decay curves for these drugs were estimates, and a curve can make tolerance look longer-lasting than it is, which is the dangerous direction.
How fast tolerance to these drugs fades after a break has not been measured well enough to draw, so don't count on a dose you used to take still being safe: after time off, start with a much smaller amount and don't use alone. Mixing sedatives with each other, with alcohol or with opioids sharply raises the risk of a fatal overdose. If you've been using regularly, don't stop suddenly: withdrawal from benzodiazepines, alcohol or GHB/GBL can cause seizures or delirium, so get medical help to cut down gradually. With barbiturates, you get used to the effects much more than to a dangerous dose, so the gap between a dose that works and one that kills shrinks the more you use. Stopping suddenly after regular use can cause convulsions and delirium.
Sources: FRANK: benzodiazepines · Alcohol and Drug Foundation: GHB · FDA 2020: benzodiazepine boxed warning · FDA 2019: gabapentinoids and breathing · NHS: alcohol use disorder · Phenobarbital label: drug abuse and dependence
Cross-Tolerances
Other barbiturates
Benzodiazepines
Effects
Effect glossary — · full glossary
Positive
Negative
Positive
Negative
Positive
Negative
Combinations
Cross-Check Phenobarbital with another substanceCommunity Trip Reports
Anecdotal first-person accounts from Reddit, Erowid, Bluelight, and Dose.wiki. Click a source to expand. Reports are harm-reduction context, not medical guidance. Tags summarise each author's own verdict — how reports are classified.
Erowid 4 reports 1 neutral 3 cautionary visit
First, let me note I am typing this from a BlackBerry about 50 minutes post dose. Also, I have a professional education in biology, chemistry, and health care practice, allowing inherent extreme familiarity with the substance(s) involved in terms of pharmacokinetics, pharmacology, and contraindications as well as recom...
My son woke up to a seizure five days ago. Although febrile seizures typically last only five or so minutes, his lasted possibly over an hour. At the hospital he received a rectal injection of Ativan (dosage unknown) which failed to stop the seizure which then prompted a 'loading dose' of phenobarbital (dosage unknown)...
I'd like to just my experiences with a certain drug called Phenobarbital. I'm a sixteen year old with an extensive trip history over the past year or so (marijuana, acid, psilocybes, amanitas, dimenhydrinate), but when I tried the drug I was an inexperienced fifteen year-old.
Pill Identifiers
35
known pill identifiers on record — view imprints, colors, shapes, and images
→
Phenobarbital's nerd page
Pharmacology, chemical data, effect profiles, and more
→
Helpful Links
Add missing routes to PsychonautWiki Journal
The PsychonautWiki Journal app already has Phenobarbital, but its built-in entry only covers Oral. Here are the other routes we have data for. You can't edit a built-in substance, but you can add a Custom Unit for any of these routes to log it.
⬇ Download import file
Import this file as custom substances
and you get "Phenobarbital (Substance Search)" with every
route's full dose ladder and timeline, no typing. Works on iOS and
Android (v15+); the format is confirmed by the app's
developer. The manual values below work for older
versions.
Duration (reference)
Phenobarbital: routes the PsychonautWiki Journal app is missing Source: SubstanceSearch (substancesearch.com) Intravenous duration: onset 5m · peak 15-30m · offset 12-24h · total 12.33-24.58h · after-effects 1-48h Note: ranges are harm-reduction guidance, not a prescription. Start low, go slow, and test your substances.
Ranges are harm-reduction guidance, not a prescription.
Report an issue or suggest an edit
Spotted incorrect or dangerous information, have a correction, a new study, or a useful addition for Phenobarbital? Let us know. Reports are reviewed by moderators — this is not posted publicly.