METHYLECGONIDINE COATS THE CRACK PARTICLE

Crack is a form of cocaine base self-administered by smoking. When hea ted, it volatilizes and may partially pyrolyze to methylecgonidine (ME G). Upon cooling, a condensation aerosol forms. Heating cocaine base i n model crack pipes produced particles of about 1 mu m in diameter, re gardless of the amount heated; however, MEG concentration increased fr om less than or equal to 2% at 10 mg per heating to as much as 5% at 3 0 mg per heating. Methylecgonidine was less than or equal to 1% of the recovered material when cocaine was vaporized off a heated wire coil, but the particles were larger (2-5 mu m), and the distribution disper se. The vapor pressure of MEG was higher [log P(mm Hg) = 9.994 - 3530/ T] than cocaine base, consistent with MEG coating the droplet during c ondensation, and with evaporation during aging or dilution. Disappeara nce of MEG from a chamber filled with crack smoke was a two-component process, one proceeding at the rate of cocaine particle removal, and t he other at the desorption rate from other surfaces. Particle diameter influences the deposition site in the respiratory tract; thus, the li kely different patterns of deposition in the respiratory tract of huma ns and animals of crack aerosols produced by different techniques warr ant consideration, as they may influence our understanding of immediat e and delayed sequelae of the inhalation of cocaine and its pyrolysis product, MEG.