Intoxication with 3-MeO-PCP alone: A case report and literature review

RATIONALE

3-Methoxyphencyclidine (3-MeO-PCP) is a new psychoactive substance derived from phencyclidine. Although it can lead to severe intoxications, the main manifestations and optimal management have not been well characterized. Here, we report 2 cases of 3-MeO-PCP intoxication in the same patient, and summarize the manifestations of this intoxication reported in literature.

PATIENT CONCERNS

A 17-year-old male purchased a bag of 3-MeO-PCP on the Internet but took an oral dose (200 mg) that corresponds to the less active isomer 4-MeO-PCP. He developed high blood pressure (158/131 mm Hg), tachycardia (100 bpm), and neurological manifestations (confusion, hypertonia, nystagmus, and then agitation). A maculopapular rash appeared, although this may have been related to the administration of midazolam. Hyperlactatemia (2.6 mmol/L) was the main laboratory finding. Seven days later, he returned to the emergency department after sniffing 50 mg of 3-MeO-PCP. High blood pressure, tachycardia, and neurological manifestations (psychomotor impairment and dysarthria) were present but less severe than after the first intoxication.

DIAGNOSIS

In the first intoxication, the blood and urine 3-MeO-PCP concentrations were, respectively, 71.1 ng/mL and 706.9 ng/mL. Conventional toxicity tests were all negative. In the second intoxication, biological samples were not available.

INTERVENTIONS

In the first intoxication, treatment consisted of intravenous hydration and midazolam. The patient was transferred to an intensive care unit for monitoring. After the second intoxication, he was monitored for 12 hours.

OUTCOMES

The patient's condition improved quickly in both cases.

LESSONS

These cases provide additional information on the manifestations of 3-MeO-PCP intoxication. These manifestations are mainly cardiovascular (high blood pressure, tachycardia) and neurological. The fact that second (50 mg) intoxication was less severe than the first (200 mg) is suggestive of a dose-effect relationship for 3-MeO-PCP. The first case also emphasizes the risk of dosing errors caused by the similarity between the names "3-MeO-PCP" and "4-MeO-PCP."

Quantitation of phencyclidine (PCP) in urine and blood using gas chromatography-mass spectrometry (GC-MS)

Phencyclidine (PCP) is a cycloalkylamine and is classified as a dissociative anesthetic. In the 1950s, PCP was tested as an intravenous anesthetic but due to its severe side effects, it was withdrawn from the clinical use. Since then PCP has become an illegal street drug making its laboratory analysis forensically essential. PCP can be detected in urine, serum, or plasma by immunoassays and quantified by gas or liquid chromatography mass spectrometry. In the method described here, a deuterated internal standard is added to the sample and the drug is extracted under alkaline conditions. Analysis is conducted using gas chromatography mass spectrometry (GC-MS). Quantitation of PCP is done by comparing the responses of unknown samples to the standards using selected ion monitoring.

A validated liquid chromatographic/tandem mass spectrometric method for the determination of phencyclidine in microliter samples of rat serum

A liquid chromatographic/tandem mass spectrometric method is described for the determination of phencyclidine (PCP) in small volumes of rat serum (e.g. 50 microl). Samples were extracted using a mixed-mode strong cation-exchange column and then separated isocratically using a narrow-bore (2.1 mm i.d.) 3 microm Hypersil phenyl column and a mobile phase consisting of an ammonium formate buffer (pH 2.7) with 60% (v/v) methanol. Detection was accomplished using positive ion electrospray ionization in the multiple reaction monitoring mode. Mass spectra were obtained and peaks were observed at an m/z (% abundance) of 244 (100), 159 (25), and 86 (89). Tandem mass spectra were also obtained from the m/z 244 precursor ion with peaks observed at m/z 159 (100), 86 (96), and 91 (11). Optimum serum PCP sensitivity and precision were obtained at a transition of m/z 244 --> 159. Matrix-associated ion suppression did not significantly affect the accuracy (100-112%) or precision (CV < or =8%) of the assay. The lower limit of quantitation was 1 ng ml(-1) in 50 microl of serum. The method was used to study the serum pharmacokinetics of PCP in rats after an intravenous bolus dose of PCP.

Reversal of phencyclidine-induced dopaminergic dysregulation by N-methyl-D-aspartate receptor/glycine-site agonists

N-methyl-D-aspartate (NMDA) receptors may play a critical role in the pathophysiology of schizophrenia. In rodents, NMDA receptor antagonists, such as phencyclidine (PCP), induce dopaminergic dysregulation that resembles the pattern observed in schizophrenia. The present study investigates the degree to which concurrent treatment with NMDA modulators, such as glycine and the recently developed glycine transport antagonist N[3-(4"-fluorophenyl)-3-(4"-phenylphenoxy)propyl]sarcosine (NFPS) prevents dopaminergic dysregulation observed following chronic (3 months) or subchronic (2 weeks) PCP administration. Both chronic and subchronic treatment with PCP in the absence of glycine or NFPS led to significant potentiation of amphetamine-induced dopamine release in the prefrontal cortex and striatum, similar to that observed in schizophrenia. Treatment with either high-dose glycine or NFPS along with PCP prevented PCP effects. These findings demonstrate effective doses of glycine for use in animal models of schizophrenia, and support recent clinical studies showing the effectiveness of NMDA agonists in the treatment of persistent symptoms of schizophrenia.

Treatment of adverse effects of excessive phencyclidine exposure in rats with a minimal dose of monoclonal antibody

The range of medical effects and complications resulting from excessive use of drugs of abuse like phencyclidine (PCP) has hindered the development of effective medications. Drug-specific monoclonal antibodies (mAbs) provide an appealing medication approach since they can be selective for the drug, without concern for the sites of action of the drug. The use of mAb medications has been considered impractical because it is commonly believed that very large doses of mAb would be required to treat the adverse medical effects resulting from excessive drug use. In this study, a single dose of an anti-PCP mAb was found to significantly reduce the negative health impact of excessive, prolonged PCP treatment in rats (18 mg/kg/day for 2 weeks). The protective effects were mAb dose-dependent, and mAb doses as low as 1/100th the molar equivalent amount of the PCP body burden were effective at preventing PCP-induced deaths, reducing PCP-induced behaviors, reducing PCP brain concentrations, and improving the general health status of the animals. They also show that treatment with monoclonal antibody medications can have medically important outcomes without the need to neutralize the entire dose of the offending drug. These results could help establish the feasibility of using carefully designed monoclonal antibody medications to treat drug abuse and addiction, a chronic and re-occurring illness of the central nervous system.

Subchronic continuous phencyclidine administration potentiates amphetamine-induced frontal cortex dopamine release

Functional dopaminergic hyperactivity is a key feature of schizophrenia. Etiology of this dopaminergic hyperactivity, however, is unknown. We have recently demonstrated that subchronic phencyclidine (PCP) treatment in rodents induces striatal dopaminergic hyperactivity similar to that observed in schizophrenia. The present study investigates the ability of PCP to potentiate amphetamine-induced dopamine release in prefrontal cortex (PFC) and nucleus accumbens (NAc) shell. Prefrontal dopaminergic hyperactivity is postulated to underlie cognitive dysfunction in schizophrenia. In contrast, the degree of NAc involvement is unknown and recent studies have suggested that PCP-induced hyperactivity in rodents may correlate with PFC, rather than NAc, dopamine levels. Rats were treated with 5-20 mg/kg/day PCP for 3-14 days by osmotic minipump. PFC and NAc dopamine release to amphetamine challenge (1 mg/kg) was monitored by in vivo microdialysis and HPLC-EC. Doses of 10 mg/kg/day and above produced serum PCP concentrations (50-150 ng/ml) most associated with PCP psychosis in humans. PCP-treated rats showed significant, dose-dependent enhancement in amphetamine-induced dopamine release in PFC but not NAc, along with significantly enhanced locomotor activity. Enhanced response was observed following 3-day, as well as 14-day, treatment and resolved within 4 days of PCP treatment withdrawal. These findings support the concept that endogenous NMDA receptor dysfunction could account for the pattern of dopaminergic dysfunction observed in schizophrenia, and suggest that even short duration abuse of PCP-like agents may greatly potentiate behavioral effects of psychostimulants in drug abuse situations. Finally, these studies provide a model system in which to evaluate effects of potential psychotherapeutic agents.

[Solid-phase microextraction for the analysis of drugs and biological samples]

Solid-phase microextraction (SPME) as a new sample pretreatment technique was developed in 1990s. The applications of SPME on drugs and biological samples are reviewed with 60 references. The references were classified into twelve groups according to the character of analysis.

[Analysis of MDMA and PCP by GC-MS from patients admitted to the critical care medical center]

In our country, abuse of methamphetamine has increased. Furthermore, dealings of other drugs by using internet have increased. But, the poison cases of 3,4-methylenedioxymethamphetamine (MDMA) and phencyclidine (PCP) have never been reported in our country. We report an MDMA poison case and a PCP poison case. We could detect MDMA, MDA or PCP by GC-MS from urine and serum of patients admitted to the critical care medical center of Nippon Medical School. Case 1: A 23-year-old foreign female was admitted to our hospital because of disturbance of consciousness. Her friend said that she had been found lying on the floor of the bathroom after taking a tablet. The screening test by Triage showed AMP positive. Not methamphetamine but MDMA and MDA were detected from urine and serum of the patient by GC-MS. Case 2: A 27-year-old foreign female was admitted to our hospital because of restlessness and excitement. Her friend said that she had become restless and excited after taking 15-30 tablets of Tylenol. The screening by Triage showed BZO and PCP positive. Not acetaminophen but PCP was detected in the patient's sample by GC-MS. Drug abuse has expanded to Japan over the border. New responses to abuse drugs with respect to medical treatment and drug analyses should be established.

Comparison of ELISAs for opiates, methamphetamine, cocaine metabolite, benzodiazepines, phencyclidine, and cannabinoids in whole blood and urine

BACKGROUND

ELISAs are widely utilized in forensic drug analysis. A comparative assessment of microtiter plate assays for the detection of six common classes of drug in blood and urine is described.

METHODS

ELISAs for opiates, methamphetamine, benzodiazepines, cocaine metabolite, phencyclidine (PCP), and tetrahydrocannabinol (THC) metabolite were evaluated in a side-by-side study. The analytical performance of 12 commercially available ELISAs was determined in terms of binding characteristics, dose-response curves, limits of detection, sensitivity, intra- and interassay imprecision, and lot-to-lot reproducibility. Assay performance was also compared using 855 forensic casework samples.

RESULTS

Detection limits in whole blood for morphine, D-methamphetamine, nordiazepam, benzoylecgonine, nordiazepam, PCP, and L-11-nor-9-carboxy-delta9-THC were 3, 2, <4, 5, 25, and 3 microg/L, respectively, for the STC ELISAs. Corresponding detection limits for Immunalysis ELISAs were <1, <2, <4, 5, <1, and 1 microg/L, respectively. Intraassay CVs (n = 8) at the immunoassay cutoff concentrations were 4.1-5.6% and 3.5-11% for STC and Immunalysis ELISAs, respectively. Corresponding interassay CVs were 3.1-10% and 6.5-20%. Of the 855 casework samples, there were a total of 92 discordant results (44 cannabinoid, 15 opiate, 15 methamphetamine, 11 benzodiazepine, and 7 cocaine metabolite). Gas chromatography-mass spectrometry analysis indicated a total of three unconfirmed positive results for Immunalysis assays and one unconfirmed positive for STC assays.

CONCLUSIONS

A comparative assessment of drugs-of-abuse assays from two manufacturers indicated some key differences in analytical performance. Overall, Immunalysis assays offered superior binding characteristics and detection limits, whereas STC assays offered improved overall precision and lot-to-lot reproducibility.

The effect of rate of drug administration on the extent and time course of phencyclidine distribution in rat brain, testis, and serum

The goal of these studies was to examine the relationship between the rate of phencyclidine (PCP) administration and PCP tissue distribution. The time course of PCP distribution in serum, brain, and testis after rapid (i.v.) and slow (s.c.) administration was studied. Brain and serum PCP concentrations after an i.v. bolus dose (1 mg/kg at 900 microg/min) were highest at 30 s and decreased biphasically, with serum concentrations decreasing 30 times faster than brain concentrations during the early phase. Consequently, the brain-to-serum PCP concentration ratio increased from 8:1 at 30 s to 14:1 at 20 min before equilibrating at a ratio of 3:1 that remained constant from 1 to 8 h. In contrast, the testis-to-serum ratio increased slowly from 1:1 to 12:1 over 4 h, and then remained constant. In a separate group of animals, an s.c. infusion of PCP (18 mg/kg/day or 3.6 microg/min) produced a brain-to-serum ratio (6:1) that remained constant throughout the 96-h infusion. Testis-to-serum ratios increased from 4:1 at 1 h to 12:1 at 8 h and then remained constant for 96 h. Steady-state infusion of a pharmacologically inactive dose (2.5 mg/kg/day) produced a brain-to-serum ratio (3:1) that was significantly lower than the ratio (6:1) after infusion of the three pharmacologically active doses (10-25 mg/kg/day). The temporary high brain PCP concentrations and the dynamic disequilibrium between brain and serum concentrations after rapid i.v. administration could provide a better understanding of the preference of the human drug abuser for rapid rates (e.g., i.v. or smoking) of drug administration.

1-[1-(2-Benzo[b]thiopheneyl)cyclohexyl]piperidine hydrochloride (BTCP) yields two active primary metabolites in vivo. Identification and quantification of BTCP primary metabolites in mice plasma, urine, and brain and their affinity for the neuronal dopamine transporter

1-[1-(2-Benzo[b]thiopheneyl)cyclohexyl]piperidine hydrochloride (BTCP) and cocaine bind to the neuronal dopamine transporter (DAT) to strongly inhibit dopamine (DA) reuptake. Although similar to acute administration, cocaine and BTCP produce sensitization and tolerance, respectively, on chronic administration. We previously found that liver microsomes produced two primary metabolites from BTCP with a high affinity for DAT. Because such metabolites, if produced in vivo, could account for the pharmacological difference with cocaine, it was important to compare BTCP biotransformations in vitro and in vivo. Therefore, we identified and quantified BTCP and primary metabolites in mice urine, plasma, and brain after acute i.p. administration. The low recovery yield suggest that BTCP might behave like its close analogue, phencyclidine, with long-term storage of metabolites. Two active metabolites found in vitro were found in mice brain with estimated half-life values similar to that of BTCP ( approximately 0.3 h). Although respective brain concentrations were 20 and 40 times lower than that of BTCP, their potency to displace in vivo [3H]BTCP bound to the DAT was 50 and 10 times higher, respectively, than that of BTCP. They could, therefore, contribute to the inhibition of DA transport and play an important role in BTCP pharmacology. They could also explain the differences between BTCP and cocaine on repeated administration.

Ultrasensitive determination of phencyclidine in body fluids by surface ionization organic mass spectrometry

Gas chromatography (GC)/surface ionization organic mass spectrometry (SIOMS) has been found to give much higher sensitivity for measurements of phencyclidine (PCP) than the conventional GC/electron impact (EI)-mass spectrometry (MS). Thus, we have established a detailed procedure for measurements of PCP in body fluids by both mass chromatography and selected-ion monitoring (SIM) of SIOMS using pethidine as an internal standard (IS). Good linearity was found in the range of 0.25-10 ng/mL of whole blood or urine, when measured by mass chromatography, and in the range of 0.025-1.0 ng/mL of whole blood by SIM. The recoveries of PCP and IS spiked to whole blood were 106 +/- 17% at 1 ng/mL and 113 +/- 11% at 5 ng/mL; that of IS was 97.8 +/- 10.4% at 5 ng/mL. The detection limits (signal-to-noise ratio = 3) were estimated to be 0.05 ng/mL of whole blood or urine by mass chromatography and 0.01 ng/mL of whole blood by SIM. The coefficients of intraday and interday variations were not greater than 10.3%. We could detect PCP from rat whole blood 2 h after subcutaneous injection of PCP (1 mg/kg) by mass chromatography. The mean PCP concentration in rat blood was 47.7 +/- 6.2 ng/mL (mean +/- SD, n = 4).

Screening postmortem blood and tissues for nine classes [correction of cases] of drugs of abuse using automated microplate immunoassay

A commercially available enzyme-linked immunosorbant assay (ELISA) was evaluated as a screening procedure for the detection of nine classes of abused drugs in postmortem blood and tissue specimens. Specifically, postmortem blood, fluid and/or tissue homogenates were screened for amphetamine (AMP), methamphetamine (MET), barbiturates (BARB), benzodiazepines (BZD), cannabinoids (CNB), cocaine (benzoylecgonine; BE), morphine-specific (MOR), opiates (class; OPI), phencyclidine (PCP) and lysergic acid diethylamide (LSD) by ELISA and by coated tube radioimmunoassay (CTR) (BARB, BE, OPI, PCP, LSD) or double-antibody radioimmunoassay (DAR) (AMP/METH, BZD, CNB). Specimens that screened 'positive' by any method were confirmed and quantitated by gas chromatography/mass spectrometry (GC/MS). The only assay that appeared to perform less optimally than RIA was the MOR assay (five false negatives). However, this assay is very specific for free morphine while the GC/MS confirmation method provided a total morphine value. The OPI assay was more sensitive, producing fewer false negatives, and is recommended for broad class opiate screening. EIA is an adequate alternative to RIA for screening postmortem specimens, including blood and tissue, for nine major classes of drugs.

Behavioral effects of chronic phencyclidine in monkeys

Phencyclidine (PCP) and other NMDA receptor antagonists such as ketamine induce psychotic symptoms that are difficult to reverse with current medications and which closely resemble those of schizophrenia. This study investigated the behavioral effects of continuous PCP administration in six socially-housed Cebus apella monkeys. Chronic treatment was associated with a sustained decrease in stereotyped locomotion (pacing) and a sustained increase in scanning behavior. Treatment was also associated with a modest decrease in self- and environment-directed behavior and goal-directed locomotion and an increase in affiliative behavior at lower doses. Four animals had one or more episodes of extreme motoric and physiological responses precipitated by stressful events. The results indicate that behavioral effects of chronic PCP in primates differ from those seen following acute treatments and represent an appropriate model system for new antipsychotic drug development.

Sexual dimorphism in phencyclidine in vitro metabolism and pharmacokinetics in rats

Studies were conducted to determine the differences in phencyclidine (PCP) in vitro metabolism and pharmacokinetics in female and male Sprague-Dawley (SD) rats. Formation rates of five major PCP metabolites in liver microsomes were significantly higher (p <.05) in males compared with females in three different rat strains (SD, Fischer 344, and Dark Agouti). In addition, the formation rate for an irreversibly bound PCP metabolite in males was the second highest of the six metabolites measured in these studies. However, the liver microsomes from the females produced essentially no metabolite binding in any strain. To determine the in vivo consequences of these in vitro metabolism results, we determined PCP's pharmacokinetic profile in female SD rats after a pharmacologically active i.v. dose of PCP (1 mg/kg) and then compared these data with the pharmacokinetic profile in male SD rats. The value for PCP systemic (and nonrenal) clearance was more than 45% lower (p <.05) in female rats. In addition, the terminal elimination T(1/2) was significantly longer (p <.05) in the female rats (5.5 versus 3.4 h, respectively). Because the initial serum concentration, volume of distribution at steady state, and renal clearance were not significantly different between the sexes, the longer half-life was attributed directly to a decreased ability of females to metabolize the drug. Consequently, these pharmacokinetic data suggest pharmacological differences in PCP effects between female and male rats are due primarily to a decreased ability of female rats to metabolize the drug.

Stability of phencyclidine in stored blood samples

A retrospective study was conducted to determine the stability of phencyclidine (PCP) in whole blood samples stored for 1-3 years at both 4 degrees C and -20 degrees C. The PCP concentrations of these samples were initially determined in 1993, 1994, or 1995, then stored until 1996, when the PCP concentrations were determined again. All quantitations of PCP were by means of gas chromatography-mass spectrometry using the internal standard method. PCP was extracted from the blood by solid-phase extraction followed by liquid-liquid back extraction. The method of quantitation for reanalysis was identical to that used in the initial PCP analyses. The results of this study reveal a tendency for the concentrations of PCP to decrease gradually over a period of 3 years. Samples stored for 1 year did not show a significant change in PCP concentration, whereas samples stored for 2 years showed a 9.6% average decrease, and samples stored for 3 years showed a 17.9% average decrease. Following storage, PCP was present in all samples in which it had been originally detected. The results of this study indicate that PCP, at the concentrations in this study, remains sufficiently stable to be detected within 3 years of storage at 4 degrees C and -20 degrees C.

Determination of gacyclidine enantiomers in human plasma by gas chromatography-mass spectrometry using selected-ion monitoring

A sensitive gas chromatographic assay using mass selective-detection has been developed for the simultaneous quantitation of the enantiomers of (+/-)-gacyclidine (a non competitive N-methyl-D-aspartate antagonist) in human plasma. Gacyclidine enantiomers and phencyclidine (PCP), the internal standard, were extracted using a single-step liquid-liquid extraction with hexane at pH 8.0. Each enantiomer was separated on a chiral gas chromatography capillary column and specifically detected by mass spectrometry (MS) in selected-ion monitoring (SIM) mode. Gacyclidine enantiomers and PCP were monitored using the fragment ions at m/z 206 and 200, respectively. No interference was observed from endogenous components. The limit of quantitation (LOQ) for each enantiomer of gacyclidine was 300 pg/ml by using plasma samples of 500 microl. The calibration curves were linear (r2=0.998) over a range of 0.3125 to 20 ng/ml. The extraction efficiency was higher than 95% for both enantiomers. Intra- and inter-day bias were less than 10% at every standard curve concentration. Intra-day precision was less than 19% for (-)-gacyclidine and 15% for (+)-gacyclidine. Inter-day precision was below 15% for both enantiomers. The assay was validated for an enantioselective pharmacokinetic study in healthy male volunteers.

Phencyclidine blood concentrations in DRE cases

Phencyclidine (PCP) concentration was measured in blood obtained from 259 individuals over a two-year period subsequent to Drug Recognition Expert (DRE) evaluation by the Maryland State Police. The purpose of this study was to evaluate the accuracy of the DRE in the identification of PCP-related impairment using the presence of PCP in blood to confirm drug use and to test for a correlation between PCP concentrations in blood and impairment as indicated by DRE evaluation. Of the 259 cases evaluated, 124 were identified as positive for PCP based on DRE evaluation, 130 were positive for PCP based on toxicological analysis, and 56 of the 124 were identified as positive for PCP only by DRE and subsequently confirmed to contain only PCP. The mean PCP concentration for those cases in which only PCP was identified by both DRE and toxicology was 51 ng/ml (standard deviation, 26 ng/mL) with a range of values of 12-118 ng/mL. Although no correlation was determined between PCP concentration and behavior, it is clear that, even at concentrations as low as 12 ng/mL, PCP-induced behavioral effects are measurable by DRE evaluation. This study also revealed that despite a low false-positive rate (3%) of detection of PCP use by the DRE, the false-negative rate of 8% supports the conclusion that the toxicological analysis of blood specimens for PCP provides the necessary, objective corroboration of the DRE's opinion concerning impairment.

Antiphencyclidine monoclonal antibody therapy significantly changes phencyclidine concentrations in brain and other tissues in rats

These studies determined how high-affinity monoclonal antiphencyclidine (PCP) antigen binding fragments of immunoglobulin G (Fab) affects PCP tissue concentrations and serum protein binding in male rats. Animals received an i.v. bolus dose of 1.0 mg/kg of PCP, followed at 2 hr when distribution was complete (but about 70% of the dose remained) by either saline (for controls) or an equimolar dose of anti-PCP Fab. This dose of PCP was chosen because it produces behavioral effects and ataxia for about 40 min. The rats were sacrificed over the next 16 hr (n = 3 per time point) and blood, brain, fat, heart, kidney, liver, lung, muscle and testis were collected. After anti-PCP Fab treatment, serum PCP concentrations increased significantly (P < .05) for the duration of the experiment. This resulted in a decrease in the PCP volume of distribution and systemic clearance to 11 and 12% of controls, respectively. Because these parameters decreased to a similar degree, the terminal elimination half-life was unaltered after Fab treatment. The percentage of unbound PCP in serum averaged 47 +/- 15% (mean +/- S.D.) in controls and 3 +/- 2% in Fab-treated animals for the duration of sampling. The area under the tissue concentration vs. time curves after anti-PCP Fab administration were decreased substantially in the brain (23% of controls), fat (24%), heart (52%), lung (74%) and testis (12%), but increased in the liver (137%). Because of anti-PCP Fab renal elimination, kidney PCP concentrations were significantly increased at all time points after Fab treatment (P < .05), which resulted in an 18-fold increase in the PCP area under the curve. These studies show anti-PCP Fab can rapidly remove PCP from the brain and maintain it in a highly bound form for a significant time.

Application of the Triage panel for drugs of abuse to forensic blood samples

A simple and rapid screening procedure with Triage has been developed to detect 7 classes of drugs of abuse, phencyclidine (PCP), benzodiazepines (BZO), cocaine metabolite (COC), amphetamines (AMP), cannabinoids (THC), opiates (OPI), and barbiturates (BAR), in hemolyzed blood. A clear supernatant was obtained by mixing the blood with sulfosalicylic acid. The supernatant was neutralized with ammonium acetate and then screened using Triage. The lower limits of detection of the Triage screening method for PCP, diazepam, benzolyecgonine, methamphetamine, morphine, 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), phenobarbital, and secobarbital were 50 ng/mL, 900 ng/mL, 1,000 ng/mL, 600 ng/mL, 900 ng/mL, and 900 ng/mL, respectively. The sensitivity of Triage for THC-COOH in deproteinized blood samples was much lower than that in urine samples. No false positive reactions were observed for the 6 classes of the drugs of abuse with the exception of AMP when the blood was decomposed. Phenethylamine, a putrefactive amine, gave positive results for AMP at concentrations over 5,000 ng/mL. The method was applied to 9 hemolyzed blood samples and 3 turbid urine samples from 12 forensic autopsy cases suspected of drug misuse. Among these, 5 were positive for AMP, 1 for OPI, and 4 for BAR. The presence of methamphetamine is only one of the 5, codeine in 1, and phenobarbital in 4 was confirmed by gas chromatography. All 4 samples which were false positive for AMP contained phenethylamine at relatively high concentrations because of moderate to heavy putrefaction. This method, although disadvantageous to test for AMP and THC, is helpful for the forensic toxicologist because any kind of bloody fluid can be tested rapidly with Triage to detect toxic levels of PCP, BZO, COC, OPI, and BAR.

Hair analysis for drugs of abuse XII. Determination of PCP and its major metabolites, PCHP and PPC, in rat hair after administration of PCP

We developed an analytical method for the simultaneous detection of phencyclidine (PCP) and its metabolites, 4-phenyl-4-piperidinocyclohexanol (PPC) and 1-(1-phenylcyclohexyl)-4-hydroxypiperidine (PCHP), in rat hair. Three pigmented, hairy rats were intraperitoneally administered PCP hydrochloride (HCl) at 0.05-0.5 mg/kg once a day for 10 successive days. Animal hair was shaved just before the first administration, and the newly grown hair was collected 4 weeks after the first administration. After the rat hair sample was washed three times with 0.1% sodium dodecyl sulfonate and water, separately, and dried in a desiccator, 20 mg of finely cut hair was extracted with 2 mL methanol-5N HCl (20:1) under ultrasonication for 1 h, followed by storage at room temperature for 14 h. Following filtration and evaporation of the extract, it was purified with Bond Elut Certify in the usual manner, and the extract was derivatized with N,O-bis(trimethylsilyl) acetamide for gas chromatographic-mass spectrometric analysis using deuterated PCP, PPC, and PCHP as internal standards. The selected ions were monitored at m/z 186, 200, and 242 for PCP, m/z 172, 288, and 331 for trimethylsilyl (TMS) PCHP, and m/z 200, 254, and 331 for TMS PPC. PCP, PCHP, and PPC were simultaneously detected in the rat hair down to 0.1 mg/kg PCP HCl. Even at the dose of 0.05 mg/kg, PCP was clearly detected in the rat hair. Based on the area under the concentration versus time curve (AUC) in plasma (1460 ng.min/mL), the PCP concentration (3.34 ng/mg) in the rat hair was quite high. The incorporation rates into hair (concentration in hair/AUC) of PCP, PCHP, and trans-PPC were 2.29, 1.65, and 0.50, respectively, at 0.5 mg/kg. Our results suggest that hair could be a useful specimen for confirmation of active past PCP use because PCP and its metabolites can be detected simultaneously.

A 5-year stability study of common illicit drugs in blood

The present study was designed to determine the stability of common illicit drugs in stored blood at various time intervals for a period of up to 5 years. The drugs of interest were cocaine and benzoylecgonine, methamphetamine and amphetamine, nonconjugated morphine and codeine, and phencyclidine (PCP). All specimens were from live individuals and were collected in gray-top Vacutainer tubes containing sodium fluoride and potassium oxalate; the tubes were stored at ambient temperature. The results of the study showed that cocaine and benzoylecgonine have poor stability and require quantitative confirmation within a reasonable time period for reliable interpretation. Methamphetamine and PCP were both fairly stable and had a high probability of confirmation upon reanalysis. The stability of nonconjugated morphine showed wide variation throughout the study. Initially, the morphine concentration decreased, then increased at the 3-year interval, and finally decreased at the 4- and 5-year intervals. The significance of the analytical findings are discussed in this report.

The effects of MK-801 on body temperature and behavior in the rat: cross-sensitization and cross-tolerance with phencyclidine

The purpose of the present study was to compare the acute and repeated administration of MK-801 (dizocilpine) on body temperature and behavior in the rat, and to determine whether there is cross-tolerance and/or cross-sensitization to phencyclidine (PCP) after repeated administration of MK-801. The acute administration of MK-801 increased body temperature, and this response was enhanced after repeated drug administration. PCP had little effect on body temperature in control rats, but produced increases in body temperature in rats treated daily with MK-801. The acute administration of MK-801 produced ataxia, locomotion, sniffing, and head-weaving, and after repeated drug administration both ataxia and head-weaving were reduced. PCP-induced ataxia, backpedalling, head-weaving, and turning behaviors were decreased in rats treated daily with MK-801, but PCP-induced locomotion and rearing were increased. These results indicate that there is cross-sensitization to the hyperthermic and locomotor effects of MK-801 and PCP, but there is cross-tolerance to some of the other behavioral effects of the drugs.

Dose- and time-dependent changes in phencyclidine metabolite covalent binding in rats and the possible role of CYP2D1

We determined whether chronic dosing with phencyclidine (PCP) could affect the in vitro function of liver microsomal enzymes in male Sprague-Dawley rats. PCP chronic dosing of rats (n = 3 per group) for 3 days with 2.5, 10 and 18 mg/kg/day caused a dose-dependent decrease (23, 36 and 53%, respectively) in the ability of the microsomal enzymes to bind covalently PCP metabolites. The 10- and 18-mg/kg/day dosing groups were significantly different from the 3-day saline-infused control group (P < .05). The results from time-dependent dosing studies indicated PCP covalent binding was significantly reduced (P < .05) in rats (n = 3 per group) infused with 18 mg/kg/day of PCP for 1, 2, 3, 4 and 10 days. Subsequently, it returned to near control values in rats infused for 20 days. In parallel with the time-dependent decreases in covalent binding, the concentrations of at least three phase I PCP mono- and dihydroxylated metabolites were also significantly reduced (P < .05) at the earlier time periods of dosing (3 and 10 days), but the rate of their formation returned to near normal values by 20 days of dosing. Total cytochrome P450 content did not differ from the control groups at any of the doses or time points. As dose- and time-dependent decreases in covalent binding suggested a specific metabolic pathway or isoenzyme was affected, we studied the affect on specific isoenzyme pathways. For these studies a series of cytochrome P450 inhibitors were used.(ABSTRACT TRUNCATED AT 250 WORDS)

Whole blood deproteinization for drug screening using automatic pipettors

Automating the initial screening of postmortem blood and other tissues for drugs of abuse requires a pipetting procedure that is compatible with immunoassay screening tests. The deproteinization procedure uses a zinc sulfate-5-sulfosalicylic acid reagent to precipitate blood proteins. This procedure for deproteinization of whole blood and tissue homogenates is compatible with coated tube radioimmunoassays (RIA) and can therefore be used in automating the initial screening step.

Protracted phencyclidine coma from an intestinal deposit

Phencyclidine is a common drug of abuse that can be taken orally, intravenously, or by inhalation. We describe a massive overdose of phencyclidine in a patient who swallowed a plastic bag containing the drug. Quantitative serum phencyclidine levels remained persistently elevated for several weeks. On hospital day 20, a plastic bag was passed via the rectum. Subsequently, the patient's serum phencyclidine levels fell in accordance with previously described pharmacokinetics. The patient rapidly recovered neurologic function. Persistently elevated serum drug levels should suggest continued drug absorption from a gastrointestinal deposit. We propose that colonoscopy and esophagogastroduodenoscopy be performed early in this setting.

Recent advances in the phencyclidine model of schizophrenia

OBJECTIVE

Phencyclidine (PCP, "angel dust") induces a psychotomimetic state that closely resembles schizophrenia. As opposed to amphetamine-induced psychosis, PCP-induced psychosis incorporates both positive (e.g., hallucinations, paranoia) and negative (e.g., emotional withdrawal, motor retardation) schizophrenic symptoms. PCP-induced psychosis also uniquely incorporates the formal thought disorder and neuropsychological deficits associated with schizophrenia. The purpose of the present paper is to review recent advances in the study of the molecular mechanisms of PCP action and to describe their implications for the understanding of schizophrenic pathophysiology.

METHOD

Twenty-five papers were identified that described the clinical dose and serum and CSF levels at which PCP induces its psychotomimetic effects. The dose range of PCP-induced effects were compared to the dose range at which PCP interacts with specific molecular targets and affects neurotransmission.

RESULTS

It was found that PCP-induced psychotomimetic effects are associated with submicromolar serum concentrations of PCP. At these concentrations PCP interacts selectively with a specific binding site (PCP receptor) that is associated with the N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptor. Occupation of its receptor by PCP induces noncompetitive inhibition of NMDA receptor-mediated neurotransmission. Other NMDA antagonists such as the dissociative anesthetic ketamine induce PCP-like neurobehavioral effects in proportion to their potency in binding to the PCP receptor and inducing NMDA receptor inhibition.

CONCLUSIONS

These findings suggest that endogenous dysfunction of NMDA receptor-mediated neurotransmission might contribute to the pathogenesis of schizophrenia. The relative implications of the PCP and amphetamine models of schizophrenia are discussed in relationship to the diagnosis and etiology of schizophrenia.

Phencyclidine dependence: the relationship of dose and serum concentrations to operant behavioral effects

The dependence-producing properties of 10 days of chronic i.v. infusions of phencyclidine (PCP) and the relationship between PCP serum concentrations and behavioral effects were studied in Sprague-Dawley rats. For dependence studies, rats were trained to respond for food under a fixed-ratio 30 schedule during half-hour response periods every 6 hr. After training, implantation of jugular catheters, and restabilization of behavior, the rats were infused with PCP.HCl at 3.2, 5.6, 10.0 or 17.8 mg/kg/day (n = 5 or 6 per dose). The two higher doses initially decreased response rates, but tolerance developed within 4 to 5 days. When PCP infusions were terminated, dose-dependent decreases in session response rate occurred in the three highest dose groups (P less than .05). Mild, overt signs of abstinence were observed only in the highest dose group. Response rates returned to base line within 2 to 3 days after stopping PCP infusions. PCP serum concentrations in rats infused with 10 mg of PCP.HCl/kg/day for 10 days were stable from hour 24 to day 10 (mean steady-state concentration (+/- S.D.) = 97 (+/- 20) ng of PCP/ml; n = 4). The average terminal elimination half-life after stopping infusions on day 10 was 4.6 hr. Comparison of the average response rates with the average serum concentrations showed that during the first 24 hr of infusions, the rate of responding for food decreased as PCP concentrations increased; however, once the animals became tolerant to PCP there was no relationship. In contrast, during the first 24 hr after stopping infusions, response rates decreased as serum concentrations decreased.

Potential error in the measurement of tissue to blood distribution coefficients in physiological pharmacokinetic modeling. Residual tissue blood. II. Distribution of phencyclidine in the rat

A model for predicting the magnitude of error (% Err) in measuring tissue concentrations of a compound that have not been corrected for residual blood in the tissue was previously developed. The model was tested using data for phencyclidine tissue distribution in the rat. It is shown that % Err may be expressed as a function of volume fraction of blood in tissue (VF)B and tissue-to-blood distribution coefficient. Correction for residual blood is important when the volume fraction of the blood in the tissue is large and when the compound is not taken up substantially by the tissue. On the other hand, a correction may not be necessary when (VF)B is small and uptake of the compound into the tissue is substantial.

Direct automated EMIT d.a.u. analysis of N,N-dimethylformamide-modified serum, plasma, and postmortem blood for amphetamines, barbiturates, methadone, methaqualone, phencyclidine, and propoxyphene

The addition of two volumes of N,N-dimethylformamide (DMF) to serum, plasma, and postmortem blood with subsequent centrifugation resulted in supernatant that could be directly analyzed by EMIT d.a.u. urine reagents on the Syva autocarousel. Application of this method to the drugs below gave cutoff concentrations in milligrams of immunochemically cross-reactive analyte equivalents/L as follows: 0.05 for amphetamine, 0.05 for secobarbital, 0.075 for methadone, 0.05 for methaqualone, 0.025 for phencyclidine, and 0.05 for propoxyphene. Quantitative "false" negative/positive noncongruence between total EMIT cross-reactants and free-drug analyses by gas chromatography/mass spectrometry were 3/4 (n = 50) for amphetamines, 2/0 (n = 60) for barbiturates, 0/0 (n = 47) for methadone, 0/0 (n = 48) for methaqualone, 1/0 (n = 44) for phencyclidine, and 1/2 for propoxyphene (n = 53). Within-day precision, as indicated by the coefficient of variation, of quantitative estimates using low and high controls ranged from 3.7 to 11% and 1.8 to 10.3%, respectively. Using the same control levels, between-day precision of quantitative estimates varied from 5.8 to 30.3% and 3.0 to 11.8%, respectively.

Effects of acute and chronic administration of (+)-SKF 10,047 on body temperature in the rat: cross-sensitization with phencyclidine

The current study investigated the effects of acute and chronic administration of (+)-SKF 10,047 on body temperature in rats. The effect of phencyclidine on body temperature in chronically (+)-SKF 10,047-treated rats was also investigated. The acute administration of (+)-SKF 10,047 at doses of 5 to 40 mg/kg s.c. did not alter body temperature; however, 80 mg/kg produced hypothermia. In contrast, chronic administration of (+)-SKF 10,047 (5-20 mg/kg) produced dose-dependent hyperthermia when tested on day 7 and 10 of chronic treatment. Moreover, sensitization to the hyperthermic effects occurred as the degree of hyperthermia was greater on day 10 compared to day 7. Phencyclidine (20 mg/kg s.c.) produced hypothermia in rats chronically treated with saline for 13 days, but hyperthermia in rats chronically treated with 20 mg/kg of (+)-SKF 10,047 for the same duration. The hyperthermic effect of chronic (+)-SKF 10,047 treatment is similar to the previously reported dose-dependent hyperthermia in chronically phencyclidine-treated animals. The cross-sensitization of chronically (+)-SKF 10,047-treated rats to the hyperthermic effects of phencyclidine supports the hypothesis that there may be common mechanisms underlying the chronic effects of these drugs on body temperature.

Phencyclidine pharmacokinetics and concentration-response relationships in the pigeon

Phencyclidine (PCP) pharmacokinetics and drug discrimination were examined in pigeons (n = 6 in both groups) after intramuscular doses of 1.48 mg/kg. PCP absorption was rapid with maximum measured plasma concentrations ranging from 559 to 1450 ng/ml at 10-30 min after dosing, which corresponded to the time of maximum PCP stimulus effects in the drug discrimination studies. The terminal elimination half-life was 0.88 hr (harmonic mean). Average values for the volume of distribution and total body clearance were 1.6 l/kg and 18.2 ml/min/kg, respectively. In the behavioral studies, pigeons discriminated PCP-like effects from about 2 min to 2 hr after dosing. An average value for response on the PCP-appropriate key and for PCP concentration at each time point from 2 min to 2 hr was calculated from the individual subject data. Least-squares linear regression analysis of these data showed a highly significant relationship between the ability to discriminate PCP and log PCP concentration (y = 103x - 219, r2 = .810, p less than 0.005). This analysis suggests PCP concentration is a good predictor of behavioral efficacy.

Simultaneous screening and quantification of several nonopiate narcotic analgesics and phencyclidine in human plasma using capillary gas chromatography

This paper describes a procedure for the quantitative determination of alfentanil, dextromoramide, fentanyl, methadone, pentazocine, pethidine, phenoperidine and phencyclidine in human plasma. Some drug metabolites were included in the study. The procedure involves a simple alkaline extraction technique and capillary gas chromatography separation followed by a nitrogen-selective detection. Concentrations as low as 10 micrograms/l can be routinely evaluated, making this method suitable for use in overdose drug screening, therapeutic drug monitoring and pharmacokinetic studies.

Screening of blood and urine for drugs of abuse utilizing diagnostic products corporation's Coat-A-Count radioimmunoassay kits

Solid-phase radioimmunoassay methods for the uniform analysis in hemolyzed whole blood and urine of opiates, methamphetamine, cocaine, free morphine, and phencyclidine using Coat-A-Count kits available from Diagnostic Products Corporation were tested for cost effectiveness without compromising the reliability of the results. Results indicate these kits are superior in performance in cross-reactivity studies, noted particularly in the methamphetamine assay, labor conservation, and cost-effectiveness to double-antibody radioimmunoassay methods.

Homicide victims in New Orleans: recent trends

Data are presented on 694 criminal homicide victims killed in the city of New Orleans during four years; 1979, 1982, 1985, and 1986. The homicide rate for black males was 6.5 times higher than that for white males for the years studied. Over 70% of victims were killed by handguns. When victims were assigned to one of five socioeconomic strata, homicide rates for blacks exceeded those for whites by a factor of at least 2.5 times for each socioeconomic stratum. White victims were more likely than were black victims to be legally intoxicated at the time of death, but black victims were nearly four times more likely to have illicit drugs other than alcohol detected. During the time period investigated, there was a marked decrease in the number of victims with pentazocine and tripelennamine ("Ts and blues") detected and an abrupt increase in the number of victims with detectable phencyclidine and cocaine levels. Further studies are needed to investigate risk factors for homicide victimization so that effective intervention strategies can be employed.

Phencyclidine pharmacokinetic scaling among species

Interspecies pharmacokinetic parameters (y) for phencyclidine [1-(1-phenylcyclohexyl)piperidine] were correlated with body weight (B) using linear regression and the allometric equation of the form y = aBx (which also may be written as the linear regression equation, log y = x log B + log a). The data were obtained from previously reported pharmacokinetic studies in mammals (i.e., humans, monkey, dog, rat and mouse) and new pharmacokinetic data for the pigeon. The animal body weights ranged from 32.5 to 77,000 g and included 6 animal species from 2 vertebrate classes. The pharmacokinetic parameters correlated with body weight were T1/2 (T1/2 = 126B0.32, r2 = 0.799), volume of distribution (V beta = 10B0.96, r2 = 0.966) and systemic clearance (CLs = 50B0.64, r2 = 0.891). In addition, clearance values were multiplied by the maximum lifespan potential (MLP) of each animal and correlated with body weight [CLs X MLP = (3.3 X 10(5))B1.0, r2 = 0.991]. This helped normalize for species differences in systemic clearance, which correlated with species longevity. These allometric equations should provide the information for scaling phencyclidine pharmacokinetic data among diverse species.

Gas-liquid chromatography of phencyclidine in serum, with nitrogen-phosphorus detection

We developed a two-step assay of phencyclidine (PCP), in which 2.5 mL of serum is adsorbed onto a disposable solid-phase extraction column and the eluted drug is determined by gas chromatography with nitrogen-phosphorus detection. Methapyriline is the internal standard. The detection limit of this technique is 0.5 microgram/L and the linear range exceeds 200 micrograms/L. Precision (CV) ranges from 30 to 10% with increasing concentration. No interferences were encountered in more than 400 clinical samples. The assay permits serial observation of low concentrations of the drug in serum for pharmacokinetic study and for quantitative clinical correlation with the Brief Psychiatric Rating Scale.

Phencyclidine in CSF and serum: a case of attempted filicide by a mother without a history of substance abuse

A previously healthy 30-year-old black woman with no history of substance abuse was hospitalized after she attempted to drown her 4-year-old son. She had become progressively confused and delusional after a flu-like illness 2 weeks before. Serum and lumbar CSF samples assayed for phencyclidine (PCP) by gas chromatography-mass spectrometry with d5 PCP as an internal standard were positive. The patient recovered rapidly after treatment with haloperidol and acidification of her urine. Suspicion of PCP abuse should remain high among patients with psychosis, even for those with no history of substance abuse.

Relationship of plasma phencyclidine levels to phencyclidine discrimination in the pigeon

Plasma phencyclidine levels were determined in pigeons trained to discriminate 1.5 mg/kg phencyclidine from saline under a second-order schedule using a color-tracking procedure. With both cumulative and non-cumulative dosing procedures, pigeons reliably discriminated plasma phencyclidine levels above 200 ng/ml. When the time course of phencyclidine discrimination was determined and compared with the time course of phencyclidine levels in plasma in a different group of birds, a similar relationship between discrimination and plasma phencyclidine was generally observed. Plasma phencyclidine levels did not correlate well with position responding observed in some birds after lower phencyclidine doses.

Drugs in fatally injured young male drivers

One or more drugs were detected in 81 percent of 440 male drivers, aged 15-34, killed in motor vehicle crashes in California; two or more drugs were detected in 43 percent. Alcohol, the most frequently found drug, was detected in 70 percent of the drivers, marijuana in 37 percent, and cocaine in 11 percent. Each of 24 other drugs was detected in fewer than 5 percent. Except for alcohol, drugs were infrequently found alone; typically, they were found in combination with high blood alcohol concentrations. The causal role of drugs in crashes was assessed by comparing drivers with and without drugs in terms of their responsibility for the crash. Alcohol was associated with increased crash responsibility; the role of other drugs could not be adequately determined.

Ethanol, marijuana, and other drug use in 600 drivers killed in single-vehicle crashes in North Carolina, 1978-1981

Although the use of ethanol, marijuana, and other drugs may be detrimental to driving safety, this has been established by direct epidemiological evidence only for ethanol. In this study, the incidences of detection of ethanol (and other volatile substances), delta-9-tetrahydrocannabinol (THC), barbiturates, cocaine and benzoylecgonine, opiates, and phencyclidine were determined in an inclusive population of 600 verified single-vehicle operator fatalities that occurred in North Carolina in 1978 to 1981. The incidence of detection of amphetamines and methaqualone were determined for drivers accepted for study during the first two years (n = 340) and the last year (n = 260), respectively. Blood concentrations of 11-nor-deta-9-tetrahydrocannabinol-9-carboxylic acid (9-carboxy-THC) were determined in THC positive drivers. EMIT cannabinoid assays were performed on blood specimens from all drivers accepted for study during the third year, and the feasibility of using the EMIT cannabinoid assay as a screening method for cannabinoids in forensic blood specimens was investigated. The incidence of detection of ethanol (79.3%) was far greater than the incidences determined for THC (7.8%), methaqualone (6.2%), and barbiturates (3.0%). Other drugs were detected rarely, or were not detected. Blood ethanol concentrations (BECs) were usually high; 85.5% of the drivers whose bloods contained ethanol and 67.8% of all drivers had BECs greater than or equal to 1.0 g/L. Drug concentrations were usually within or were below accepted therapeutic or active ranges. Only a small number of drivers could have been impaired by drugs, and most of them had high BECs. Multiple drug use (discounting ethanol) was comparatively rare. Ethanol was the only drug tested for that appears to have a significantly adverse effect on driving safety.

The dispositional kinetics of phencyclidine and its N-ethylamine analogue in rats

The uptake kinetics of [3H]-labelled phencyclidine (PCP) and N-ethyl-l-phenycyclohexylamine (PCE) in rats, measured in terms of decreases in the blood concentrations of the drugs after i.v. administration of a single 1.09 mumol dose, were not significantly different. Within a week of administration, the rats excreted about 93% of the [3H]-PCP and about 65% of [3H]-PCE via their urine and faeces; their urine contained nore [3H], mainly as metabolites of [3H]-PCP and of [3H]-PCE, than their faeces. Similarly, more [3H] remained in the tissues of rats treated with [3H]-PCE than in the tissues of [3H4-PCP-treated rats. The fact that PCE is metabolized and excreted more slowly than PCP may account for the higher psychotropic effects of PCE.

Phencyclidine blood protein binding: influence of protein, pH and species

We studied the influence of protein, pH and species on phencyclidine (PCP) protein binding. PCP binding to dog serum was unaffected by high concentrations of PCP and metabolites. The percentage of unbound PCP in pooled human serum and plasma specimens and pooled dog serum specimens was (mean +/- S.D.): 48.3 +/- 2.5; 42.5 +/- 1.8; and 43.3 +/- 1.9%, respectively. The percentage of unbound PCP in human serum albumin (HSA), 81.2 +/- 2.0%, was constant over the physiological HSA concentration range (3.5-5.5 g/dl). The binding of PCP to alpha 1-acid glycoprotein (alpha 1-AGP) increased with increasing alpha 1-AGP concentration (50-200 mg/dl). The binding to HSA or alpha 1-AGP separately did not account for the binding found in whole serum or plasma specimens. However, when a constant concentration of HSA (4.5 g/dl) was added to varying concentrations of alpha 1-AGP, the PCP binding increased dramatically and was similar to the binding found in human serum specimens. The association constant in the presence of both proteins (7.72 X 10(4) M-1) was 4.4 times greater than the association constant for alpha 1-AGP alone (1.74 X 10(4) M-1). This suggested an interaction between the proteins which resulted in enhanced PCP binding. The percentage of unbound PCP increased with decreasing pH in both dog serum and human serum specimens. This change could have possible effects on PCP distribution and elimination. The PCP blood to plasma ratio was 0.94 in pooled human heparinized blood and 1.25 in pooled dog heparinized blood. Neither species showed PCP concentration-dependent partitioning.