The bioavailability of intranasal and smoked methamphetamine.
BACKGROUND
Patients in harm-reduction treatment programs are switching from intravenous to other routes of methamphetamine (INN, metamfetamine) administration to avoid risks associated with needle use. Relatively little has been reported about the bioavailability of methamphetamine when smoked or used intranasally.


METHODS
Eight experienced methamphetamine users were administered smoked or intranasal methamphetamine concurrently with an intravenous dose of deuterium-labeled methamphetamine. Plasma and urine concentrations were measured for calculation of bioavailability and other pharmacokinetic parameters by noncompartmental methods.


RESULTS
Methamphetamine was well absorbed after smoking or intranasal administration, with bioavailabilities of 79% after intranasal administration and 67% of the estimated delivered dose or 37.4% of the absolute (pipe) dose after smoking. Maximum methamphetamine concentrations occurred at 2.7 and 2.5 hours after intranasal and smoked doses. The elimination half-life was similar for intravenous (11.4 hours), intranasal (10.7 hours), and smoked (10.7 hours) methamphetamine. Clearance (272 mL x h(-1) x kg(-1)), steady-state volume of distribution (4.2 L/kg), and mean residence time (16 hours) of the intravenous dose were similar to previously reported values. Dextroamphetamine (INN, dexamfetamine) half-life (all routes) was 16.2 hours. Methamphetamine and dextroamphetamine renal clearances (all routes) were about 100 and 1100 mL x h(-1) x kg(-1), respectively.


CONCLUSIONS
Intranasal and smoked methamphetamine are well absorbed. Although intranasal or smoked routes may decrease the risk of transmission of blood-borne diseases, exposure to methamphetamine and the possibility of drug-related complications remain substantial.
Harris
Debra S
DS
Drug Dependence Research Center, Langley Porter Psychiatric Institute, University of California, San Francisco, CA 94143-0984, USA.
Boxenbaum
Harold
H
Everhart
E Thomas
ET
Sequeira
Gina
G
Mendelson
John E
JE
Jones
Reese T
RT
D000280:Administration, Inhalation; D000281:Administration, Intranasal; D000328:Adult; D019540:Area Under Curve; D001682:Biological Availability; D001794:Blood Pressure / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000493:pharmacokinetics; D005059:Euphoria / Q000187:drug effects; D006207:Half-Life; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D007553:Isotope Labeling; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D008875:Middle Aged; D012906:Smoke
D000697:Central Nervous System Stimulants; D012906:Smoke; D008694:Methamphetamine; D003913:Dextroamphetamine