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Biomedical subjects

R L Hawks

Publications and source records attributed to R L Hawks.

8 recordsLinked to original sources
PubMed1986

Implications of drug levels in body fluids: basic concepts.

Drug concentrations in biological fluids are affected by the dose, route of administration, pattern of drug use, and the dispositional kinetics (distribution, metabolism, and excretion) of the drug. As most drugs are distributed to the site of action by blood, drug concentration measurement in this body fluid provides the best information as to the potential effect on behavior such as driving impairment or on psychological high. Due to wide individual variations in the pharmacokinetics and pharmacodynamics of drugs, however, the use of plasma drug concentrations for the estimation of impairment has not been established for most drugs. As for urinalysis, drug concentrations in the urine are further complicated by other factors such as urine flow and pH. Even if a specific method is used for the quantitation of a specific drug (the active species, not the inactive metabolite), interpretation in forensic samples to predict time of drug use or impairment is not possible, except within broad time periods, because of the variations in urine drug concentration as well as the limited knowledge available about the dose or the route of administration.

Body Fluids↗
PubMed1985

Laboratory detection of marijuana use.

Frequent smoking of cannabis (marijuana) has been shown to be associated with a decline in social, mental, and perceptual skills and, during adolescence, with maladaptive emotional development. Urinalysis for the detection of such use can be a useful tool for the physician responsible for treatment and counseling of adolescents who develop habitual use of marijuana. Primary methods for urinalysis detection of cannabis use include the homogeneous enzyme immunoassay (EMIT) and the radioimmunoassay. These and other methods are discussed along with the issues of "false" results (both positive and negative) and the "limits of interpretation" that can be placed on a positive urine result. The pharmacokinetics and metabolism of the active constituents of cannabis are described as well as the interpretation of urinalysis results as they relate to use patterns. Guidelines are presented for the primary care physician for selecting candidates for such testing and for the use of such tests in the treatment or counseling of adolescents for whom marijuana abuse has become a psychological and social problem.

Cannabinoids↗
PubMedDate not supplied

Assessment of laboratory quality in urine drug testing. A proficiency testing pilot study.

As part of a program to develop accreditation guidelines for urine drug testing laboratories, a pilot study for proficiency testing was conducted. Fifty civilian, commercial laboratories were included on a voluntary basis. Drug-free urine specimens were collected and either fortified with commonly abused drugs at concentrations comparable to casual use or submitted unfortified to participating laboratories as blanks. Samples were submitted on both an open and blind basis to the laboratories. Laboratory performance on open proficiency testing was comparable with that reported in existing proficiency testing programs. Blind proficiency testing produced less accurate results in terms of apparent false-negatives, but significant difficulties were evident in carrying out blind testing and in comparing its results with those of open testing. Specific problems have been identified to guide future programs.

False Negative Reactions↗