Methamphetamine Bioavailability by Route of Administration

[smfadmin (OP)]

Methamphetamine Bioavailability by ROA

IV (Injection): ~100% 
Direct systemic entry. Highest vascular + infection risk.

Smoking (Freebase Vapor): ~90–98% 
Fastest onset + hardest reinforcement loop (most addictive).

Insufflated (Snorted): ~70–90% 
Varies with pH + technique. Chronic sinus damage common.

Oral (Swallowed): ~62–79% 
Smoothest curve, longest duration, lowest compulsion spike.

Rectal (Plugging): ~70–80% 
Avoids most first-pass. Stronger and faster than oral.

Sublingual / Buccal: ~50–60% 
Most swallowed; inconsistent absorption.

IM (Intramuscular): ~80–90% 
Slower than IV, weaker rush. Infection risk still present.


Onset & Reinforcement Profiles

Smoking / IV: Seconds | Highest DA spike → strongest addiction loop 
Snorted / Rectal: 3–10 min | Moderate reinforcement 
Oral: 20–45 min | Lowest reinforcement, more stable use pattern


Harm Reduction Guidance

• If aiming to control tolerance → choose Oral or Rectal 
• Smoking and IV accelerate tolerance fastest 
• Keep minimum 72 hours spacing between runs 
• Avoid stacking stimulants with sleep deprivation


Supplements That Provide Actual Benefit

• Magnesium – NMDA regulation 
• NAC – reduces oxidative stress + glutamate dysregulation 
• DHA / Omega-3 – neuronal membrane stabilization 
• Vitamin C – antioxidant + post-run recovery 
• Adequate Sleep – mandatory for synaptic reset


Summary: 
Snorting wastes drug + damages tissue. 
Smoking/IV = strongest dopamine spike → steep tolerance ramp. 
Oral/Rectal = smoother kinetics → easiest to keep usage functional.