Routes of Administration
How a substance enters the body fundamentally changes the experience. The same dose by different routes can range from barely noticeable to life-threatening.
A dose without its route is dangerous. Psychedex always shows dose ranges paired with their ROA. If you see a dose number without a route specified, do not use it — the dose for oral use may be dangerous when insufflated, and fatal when injected.
key concepts
Bioavailability
The fraction of a dose that reaches systemic circulation. 100% for IV (by definition), variable for all other routes. Higher bioavailability means you need less substance for the same effect.
First-pass metabolism
When substances are swallowed, they pass through the liver before reaching the bloodstream. The liver metabolizes some of the substance, reducing the amount that reaches the brain. Routes that bypass the GI tract (sublingual, rectal, IV) avoid this.
Onset speed → addiction potential
Faster onset correlates with higher addiction potential. The brain associates rapid reward delivery with higher reinforcement value. This is why smoked and injected forms of substances are more addictive than oral forms.
Duration trade-off
Faster onset generally means shorter duration. Oral use typically produces the longest experience. IV and smoked produce the shortest.
Oral(swallowed, ingested, eaten)
onset
20–90 minutes (varies by stomach contents)
duration
Longest duration of most ROAs
bioavailability
Variable (30–100% depending on substance and first-pass metabolism)
risks
–Nausea, especially on an empty stomach
–Unpredictable onset time leads to impatient redosing — the most common cause of accidental overdose
–First-pass liver metabolism reduces bioavailability for some substances but can also create active metabolites
The safest ROA for most substances. Slower onset gives more time to assess effects before the full dose takes effect. Wait for full onset before considering any additional dose.
Sublingual / Buccal(under the tongue, in the cheek)
onset
5–30 minutes
duration
Slightly shorter than oral for most substances
bioavailability
Higher than oral for substances with high first-pass metabolism
risks
–Irritation or chemical burns to oral mucosa (especially with caustic substances)
–Bitter or unpleasant taste
–Difficulty holding substance in place for required absorption time
Bypasses first-pass liver metabolism, increasing bioavailability. Absorption occurs through the mucous membranes directly into the bloodstream. Commonly used for LSD (blotter), some benzodiazepines, and buprenorphine.
Insufflated(snorted, nasal, intranasal)
onset
2–15 minutes
duration
Typically shorter than oral
bioavailability
Generally higher than oral (50–90%)
risks
–Nasal tissue damage with repeated use (septal perforation, chronic nosebleeds)
–Risk of infection from shared straws or contaminated surfaces
–Drip into throat can cause nausea
–Faster onset increases addiction potential
–Dose calibration is harder — absorption rate varies with nasal congestion
Rapid onset through nasal mucosa. Use clean, personal straws (not rolled banknotes which carry bacteria). Alternate nostrils. Rinse nasal passages with saline after use. Crushed tablets may contain binders that damage nasal tissue.
Inhaled / Smoked(smoked, vaped, vaporized)
onset
Seconds to 2 minutes
duration
Usually the shortest duration of any ROA
bioavailability
Highly variable (depends on technique, temperature, substance)
risks
–Near-instant peak — no time to assess before full effect
–Lung damage from combustion products (smoke)
–Highest addiction potential due to fastest onset
–Difficulty controlling dose — each hit delivers variable amounts
–Risk of burns from equipment
The fastest ROA. Vaporization (heating without combustion) is less harmful to lungs than smoking. The extremely rapid onset makes this ROA high-risk for substances with a narrow therapeutic index. Start with a very small amount.
Rectal(plugged, boofed)
onset
5–20 minutes
duration
Similar to oral, sometimes shorter
bioavailability
Higher than oral for most substances (bypasses some first-pass metabolism)
risks
–Tissue irritation or damage to rectal mucosa
–Difficulty measuring exact dose absorbed
–Risk of infection if hygiene is poor
Bypasses most first-pass liver metabolism. Use an oral syringe for measured dosing. Dissolve substance in a small volume of warm water (1–3 ml). Higher bioavailability means oral doses may be too high for this ROA — reduce dose accordingly.
Intramuscular (IM)(injected into muscle)
onset
3–10 minutes
duration
Similar to or slightly shorter than oral
bioavailability
Near 100%
risks
–Infection risk (abscess, cellulitis) if sterile technique is not used
–Tissue damage from repeated injection or irritating substances
–Nerve damage if injection site is incorrect
–No way to reduce dose once injected
Primarily relevant for ketamine (medical and non-medical use). Requires knowledge of safe injection sites and sterile technique. Always use new, sterile needles. Never share injection equipment.
Intravenous (IV)(injected, mainlined)
onset
15–30 seconds
duration
Usually shortest duration
bioavailability
100% by definition
risks
–Highest risk ROA: overdose, infection, vascular damage, embolism
–No time to assess effects — full dose hits immediately
–Vein damage, collapsed veins, scarring from repeated use
–Highest risk for bloodborne infections (HIV, hepatitis) from shared equipment
–Highest addiction potential alongside smoking
–Fatal overdose is fastest by this route
If you inject: always use new, sterile equipment. Never share needles, syringes, cookers, filters, or water. Use sterile water for preparation. Rotate injection sites. Seek out needle exchange programs. Have naloxone available if using opioids. Consider safer ROAs — this is harm reduction, not endorsement of this route.
Transdermal(patch, topical absorption)
onset
30 minutes to several hours
duration
Extended release over hours to days
bioavailability
Varies widely by substance and formulation
risks
–Fentanyl patches are particularly dangerous if misused — heating, cutting, or chewing releases the entire dose at once
–Slow onset can lead to impatient redosing
–Skin irritation at application site
Primarily relevant for pharmaceutical fentanyl patches and nicotine patches. Designed for slow, sustained release. Misuse of transdermal patches (especially fentanyl) is extremely dangerous.
Oral administration is the safest ROA for most substances. Each step toward faster onset increases both risk and addiction potential. Choosing a slower ROA is one of the most effective harm reduction decisions available.