The incorporation of drugs into hair: Relationship of hair color and melanin concentration to phencyclidine incorporation

Rodents with different hair pigmentation patterns were studied to evaluate the role of melanin in the incorporation of phencyclidine (PCP) into hair. There are two types of melanin in hair and other tissues: eumelanin, a brown-black pigment and pheomelanin, a reddish-yellow pigment. Sprague Dawley (SD; nonpigmented), Dark Agouti (DA; brown), Copenhagen (CP; brown hooded), Long Evans (LE; black hooded), and LBNF1 (deep brown) rats and Swiss- Webster (SW; nonpigmented), C578L6 (black), and C578L6 Ay/a (yellow) mice were administered PCP at 10 mg/kg/day for 5 days (n = 5 for each strain). Hair was collected either 14 (rats) or 35 (mice) days (mice) after beginning drug administration and analyzed for PCP, eumelanin, and pheomelanin. PCP concentrations in ng/mg (mean ± SEM) were as follows: SD, 0.46 ± 0.13; DA, 12.25 ± 1.24; CP nonpigmented, 0.12 ± 0.004; CP pigmented, 9.16 ± 2.8; LE nonpigmented, 0.66 ± 0.07; LE pigmented, 21.2 ± 1.4; LBNF1, 21.64 ± 3.8; SW, 0.48 ± 0.36; C57 black, 11.0 ± 4.03; and C57 yellow, 2.26 ± 0.55. Eumelanin concentrations in μg/mg (mean ± SEM) were as follows: DA, 20.50 ± 1.58; CP pigmented, 19.43 ± 0.40; LE pigmented, 17.56 ± 0.61; LBNF1, 27.26 ± 2.52; C57 black, 37.33 ± 3.61; and C57 yellow, 1.76 ± 0.02. Eumelanin was not detected in nonpigmented hair. Pheomelanin concentrations in μg/mg (mean ± SEM) were as follows: DA, 0.09 ± 0.00; CP pigmented, 0.20 ± 0,03; LBNF1, 0.06 ± 0.01; C57 black, 0.16 ± 0.05; and C57 yellow, 29.16 ± 0.97. Pheomelanin was not detected in nonpigmented or LE pigmented hair. These data demonstrate that PCP is incorporated into black hair to a greater extent than yellow or nonpigmented hair. There appears to be a linear relationship between the PCP concentration in hair and the ratio of eumelanin to pheomelanin. Our data suggest that despite variations in PCP concentration because of hair color, they may be normalized by using the ratio of eumelanin to pheomelanin rather than hair weight.