Edibles dosing — first-pass metabolism, onset times, and the dose-stacking trap

When you inhale cannabis, THC enters pulmonary circulation, reaches the brain in 30-90 seconds, and produces effects within minutes. The molecule that produces those effects is Δ9-THC itself.

When you eat cannabis, THC enters the gastrointestinal tract, gets absorbed across the intestinal wall, and is delivered to the liver via the portal vein. The liver's CYP2C9 and CYP3A4 enzymes convert THC to 11-hydroxy-THC (11-OH-THC), which then enters systemic circulation.

11-OH-THC has approximately 2-3x the CB1 affinity of THC and crosses the blood-brain barrier more readily. Plasma concentrations of 11-OH-THC after oral THC are typically higher than the parent THC molecule itself.

So an edible doesn't just deliver "THC delayed by an hour." It delivers a more potent, longer-lasting metabolite at higher concentrations than inhalation. The same milligram dose produces a stronger and longer experience.

Onset times:

• Inhaled: 1-5 minutes to peak; effects 1-3 hours
• Sublingual (tincture, lozenge): 15-45 minutes; effects 3-6 hours
• Oral (gummy, brownie, capsule): 30-120 minutes; effects 4-8 hours
• Oral on full stomach: up to 3-4 hours to onset; effects 6-10 hours

The single most common emergency-room cannabis presentation in legal-state hospitals is acute over-intoxication from edibles. The mechanism is virtually always the same: a user takes a dose, doesn't feel effects within 30-60 minutes, takes more, and 90 minutes after the first dose finds themselves with 2-3x the intended dose hitting at once.

This is so predictable it's worth memorizing as a single rule:

Wait at least 2 hours before re-dosing oral cannabis.

If after 2 hours you feel effects but want more, take 25-50% of the original dose, never another full dose. If after 2 hours you feel nothing, your stomach contents may be delaying absorption — wait another 30-60 minutes before deciding.

Dose-stacking is particularly dangerous for first-time edible users, who don't have a baseline expectation of what onset feels like. It's also more dangerous in older users (slower hepatic clearance) and users on medications that inhibit CYP3A4 (grapefruit juice, certain antifungals, certain HIV medications).

Published harm-reduction guidance and the National Academies of Sciences cannabis report converge on similar starting doses:

Cannabis-naïve adult, age 18-50, no relevant medications:

• 2.5 mg THC oral (sub-clinical for most users; ensures no overshoot)
• Wait 2 hours
• If no/mild effect: take an additional 2.5 mg, wait 2 more hours
• Build to comfortable dose over multiple sessions, never within a single session

Adult with prior cannabis experience but no edibles experience:

• 5 mg THC oral starting
• Same waiting protocol
• 5-10 mg is the typical "moderate" dose for an experienced user

Older adults (60+):

• 1-2.5 mg THC starting
• Watch for cardiovascular effects; THC can cause tachycardia
• Many older adults find 5 mg provides full experience

For sleep specifically:

• 2.5-5 mg of a CBD:THC product (1:1 or higher CBD ratio works well)
• Take 60-90 min before intended bedtime
• Higher doses can disrupt sleep architecture (less REM, more deep sleep) — not always desirable

What you absolutely should not do as a first-time edibles user: take a 25 mg cookie that "everyone says is one serving." 25 mg is a high dose for an experienced user. For a naïve user it's a 4-8 hour panic attack waiting to happen.

Acute cannabis over-intoxication is psychologically distressing but not medically dangerous. There are no documented fatalities from cannabis alone (in healthy adults; very young children are different). What feels like a medical emergency is panic on top of cognitive distortion. Knowing this in advance is itself protective.

If you or someone else has taken too much:

1. Get to a calm, safe environment. Lie down. Dim lights.
2. Hydrate. Water, not alcohol or stimulants.
3. Eat something. Reduces continuing absorption.
4. CBD may help. 25-50 mg CBD orally has been shown to reduce subjective THC intensity (Englund 2013).
5. Talk to someone calm. Reassurance that this will pass is genuinely effective.
6. Effects peak 2-4 hours after the dose, then taper over the next 4-6 hours. Tell yourself this; it's accurate.

When to actually go to an ER:

• Chest pain, severe shortness of breath, or sustained heart rate >130
• Persistent vomiting (cannabis hyperemesis is real)
• Loss of consciousness or inability to swallow
• Suspicion of additional substances (other drug, alcohol, etc.)

For most cases, "the worst panic of my life" passes in 6-12 hours and produces no lasting harm. The biological constants are reassuring; the subjective experience is the hard part.

Cannabis interacts with several common medications. The interactions matter clinically:

CYP3A4 inhibitors (raise cannabis levels):

• Grapefruit juice
• Certain antibiotics (clarithromycin, erythromycin)
• Certain antifungals (ketoconazole, itraconazole)
• Certain HIV medications

CYP3A4 inducers (lower cannabis levels):

• Rifampin
• Carbamazepine, phenytoin, phenobarbital
• St. John's Wort

Direct interactions:

• Warfarin: cannabis can elevate INR (bleeding risk). Monitor closely.
• Sedatives (benzodiazepines, opioids): additive sedation, additive respiratory depression
• Stimulants (Adderall, Ritalin): unpredictable cardiac effects in combination

If you take any prescription medication regularly, check the specific cannabis-drug interaction with your pharmacist. Most pharmacists are now familiar with cannabis interactions.