Cocaine metabolites in the neonate: potential for toxicity

Prenatal exposure: The effects of prenatal cocaine and methamphetamine exposure on the developing child

Prenatal substance use remains a significant issue in the United States. Initial reports regarding prenatal cocaine and methamphetamine exposure suggested profound adverse effects on child development. However, subsequent prospective, longitudinal investigations have found more subtle effects. What follows is a brief review of the health, growth, behavioral, and intellectual outcomes for children exposed to prenatal cocaine and prenatal methamphetamine. Factors that may mitigate or intensify subtle adverse effects manifested in exposed children will also be discussed. Birth Defects Research (Part C) 108:142-146, 2016. © 2016 Wiley Periodicals, Inc.

Cocaine and its metabolites in the placenta: a systematic review of the literature

It is clear that cocaine and cocaine metabolites are present in the placenta and may harm the fetus. The results of the experimental manipulation of cocaine exposure are not reported in the literature in a consistent manner. We conducted a systematic review of selected articles that demonstrated the analytical detection of cocaine and its metabolites in the placenta and that were published from January 1, 1956-June 30, 2011 using Medline, Toxline and Scopus databases. The collected data confirm that the placenta does not act as a barrier to fetal exposure, that cocaine quickly crosses the placenta and that one of the essential roles of the placenta is to metabolize cocaine during pregnancy. Our systematic review summarized the results showing that cocaine, benzoylecgonine and norcocaine are stored in the myometrium and the placental membrane and maintain continuous drug delivery to the amniotic fluid (and to the fetus) probably via diffusion.

A biomarker validation study of prenatal chlorpyrifos exposure within an inner-city cohort during pregnancy

BACKGROUND

We previously documented significant decreases in chlorpyrifos concentrations in maternal personal and indoor air samples among pregnant African-American and Dominican women from New York City after the 2000-2001 restrictions on its residential use.

OBJECTIVE

We undertook a biomarker validation study within the same cohort to evaluate trends over time in multiple biomarkers of prenatal chlorpyrifos exposure.

METHODS

Subjects were enrolled between February 2001 and May 2004 (n = 102). We measured 3,5,6-trichloro-2-pyridinol (TCPy) in postpartum meconium (n = 83), repeat prenatal maternal spot urine samples (n = 253), and postnatal urine from the mothers (n = 73) and newborns (n = 59). We measured chlorpyrifos in postnatal maternal (n = 92) and umbilical cord (n = 65) blood.

RESULTS

We did not detect TCPy in infant urine, but all other biomarkers showed a highly significant decrease in detection frequencies (chi2 = 7.8-34.0, p < or = 0.005) and mean ranks (p < or = 0.006, Kruskal-Wallis) among subjects enrolled in 2003-2004 compared with those enrolled in 2001-2002. Chlorpyrifos in maternal personal and indoor air declined 2- to 3-fold over the same period (p < 0.05). In 2001-2002 samples, TCPy levels in repeat prenatal urine were positively correlated (r = 0.23-0.56), but within-subject variability exceeded between-subject variability (intraclass correlation coefficient = 0.43); indoor air levels explained 19% of the variance in prenatal urine TCPy (p = 0.001). Meconium TCPy concentrations were positively correlated with chlorpyrifos in maternal and cord blood (r = 0.25-0.33, p < 0.05) and with TCPy in maternal urine (r = 0.31, p < 0.01).

CONCLUSIONS

Results suggest the biomarkers are reliable dosimeters to differentiate between groups with prenatal chlorpyrifos exposures varying by a factor of 2 or more and vividly illustrate the efficacy of residential restriction on chlorpyrifos to reduce the internal dose during pregnancy.

Drugs of abuse testing in meconium

Prenatal substance abuse is an ongoing concern with significant impact on neonatal health and development across socioeconomic lines. Meconium, passed by neonates during their first post-natal bowel movements, is a matrix unique to the developing fetus and contains a long history of prenatal metabolism. Over the last two decades, the use of meconium as a matrix for assessing prenatal exposure to drugs of abuse has yielded methods exhibiting higher sensitivity, easier collection, and a larger window of detection than traditional matrices. Recently, a method has been developed for the analysis of fatty acid ethyl esters in meconium as a biomarker of fetal alcohol exposure, potentially facilitating the future diagnosis of Fetal Alcohol Spectrum Disorder in situations where gestational alcohol consumption history is unknown. Screening for prenatal exposure to illicit and abused licit drugs in meconium is possible by use of a variety of immunoassay methods with conformational analysis usually occurring by GCMS or LCMS. In spite of increased sample preparation time relative to blood and urine, the long metabolic history, coupled with the ease and wide window of collection of meconium make it the ideal matrix for determining fetal drug exposure.

Relative ability of biologic specimens and interviews to detect prenatal cocaine use

For this study, we recruited women admitted to our labor and delivery service, enrolling all consenting patients with a history of prenatal cocaine use and the next admission with no recorded use. During the immediate postpartum period, experienced researchers conducted private, structured interviews to obtain details of prenatal cocaine use and to identify a priori exclusion criteria (other illicit drug use, high alcohol use and chronic illnesses and medications). Specific protocols were used to collect amniotic fluid, cord blood, infant urine, meconium and maternal hair. All specimens were analyzed blind with respect to exposure using gas chromatography/mass spectrometry. Of 115 subjects, 46 had one or more biologic specimens positive for cocaine metabolites and five admitted prenatal use, but had negative specimens. Of these 51 identified as users by any method, 38 admitted, 32 were positive for urine, 28 for hair and 25 for meconium. Of the 38 admitters, 87% had positive specimens; of the 77 denying use, 17% were positive. Urine was most frequently positive in identified users, 67% overall and 62% of users who denied. Hair was next, positive in 65% of all users and 50% of users who denied. Of the 13 subjects who denied use but were positive on at least one specimen, four were identified solely by urine, two only by hair and one only by meconium. Self-report identified five users with all negative specimens. Although no one method identified all users, the single method that maximally identified users was detailed history taken by experienced interviewers.

Fetal Alcohol and Drug Effects

BACKGROUND

Alcohol and drug use by pregnant women are harmful to the developing embryo and fetus. Teasing apart the specific contributions of each substance to adverse child outcome, however, proves difficult in practice. The risks to the neonate include intra-uterine growth retardation, birth defects, altered neurobehavior, and withdrawal symptoms. Subsequent behavior, development, and neurologic function may also be impaired.

REVIEW SUMMARY

Maternal cigarette smoking carries the greatest risk of impaired fetal growth of any of the substances discussed herein and has been linked to subsequent externalizing behaviors. Alcohol is a well-established teratogen. Heavy exposure to alcohol in a subset of infants is associated with fetal alcohol syndrome (FAS). Mental retardation is one of the main sequelae of alcohol exposure in utero. Fetal marijuana exposure has no consistent effect on outcome. Prenatal cocaine exposure has not been shown to have any detrimental effect on cognition, except as mediated through cocaine effects on head size. Although fetal cocaine exposure has been linked to numerous abnormalities in arousal, attention, and neurologic and neurophysiological function, most such effects appear to be self-limited and restricted to early infancy and childhood. Opiate exposure elicits a well-described withdrawal syndrome affecting central nervous, autonomic, and gastrointestinal systems, which is most severe among methadone-exposed infants.

CONCLUSION

Most adverse effects of prenatal drug exposure are self-limited, with catch-up growth and resolution of withdrawal and of prior neurobehavioral abnormalities noted over time. The exception is alcohol, which is linked to life-long impairments (i.e., mental retardation and microcephaly) and possibly cigarette-related behavioral effects. The absence of tangible evidence of detrimental long-term cocaine effects may reflect limitations in the methodology used to identify children at greatest risk for adverse outcome.

Newborn evaluations of toxicity and withdrawal related to prenatal cocaine exposure

The literature on prenatal cocaine exposure is unclear whether immediate postpartum effects on the infant are transient, related to either acute toxicity of cocaine, or to a withdrawal effect as cocaine is metabolized, or whether they might persist. This prospective, longitudinal study was designed to test the hypotheses that newborns urine-positive for cocaine metabolites, compared to those exposed but urine-negative, and to nonexposed controls would (1) have poorer neurobehavioral scores (toxicity effect) and (2) worsen or demonstrate less improvement over the first week (withdrawal effect). We approached over 2500 pregnant women designated to deliver at our referral hospital from public health clinics; 85% consented to participate in a longitudinal study. We excluded women <18 years old with major chronic illness and prenatal drug use except cocaine, marijuana, alcohol and tobacco. From positive urine toxicologies or admissions in private, thorough interviews, 154 were identified as prenatal cocaine users; 154 were selected from noncocaine users matched on socioeconomic status (SES), race, parity and location of prenatal care (that related to perinatal risk), for a total sample size of 308. Included in this article are the 155 surviving infants who were full-term, delivered vaginally and were well and available for testing over the first week postpartum. Infant urine specimens were collected, and neurobehavorial testing was performed by certified, blinded examiners using the Neonatal Behavioral Assessment Scale on days 1, 2-4 and 5-7 postpartum. In toxicity analyses, controlling for amount of prenatal drug exposures, only autonomic regulation demonstrated significant overall and cocaine drug group effects. Urine-positive newborns had the poorest scores (i.e., more startles, tremors). However, given that planned comparisons were not significant, these data provided little support for acute toxicity effects. In withdrawal analyses, only one significant change over time varied among exposure groups. Those infants exposed and positive for cocaine metabolites increased their scores on regulation of state on days 2-4 and decreased them on days 5-7 (when withdrawal might be evident). However, their scores on days 5-7 were not significantly lower than their initial scores, nor different from the days 5-7 scores of the exposed negatives or control infants, lending little support for withdrawal effects. Our data support those of other controlled studies in failing to demonstrate devastating early effects of prenatal cocaine exposure. They add to our understanding that effects observed do not appear to be related to acute toxicity nor to cocaine withdrawal. The uncertainty of persistent effects of cocaine exposure warrants long-term follow-up.

The disposition of benzoylecgonine in maternal and fetal rats

We tested our hypothesis that pregnancy alters the pharmacokinetic profile of benzoylecgonine, and that this metabolite accumulates in the fetus longer than in the mother. Chronically catheterized near-term pregnant and nonpregnant female Sprague-Dawley rats received an intravenous infusion of benzoylecgonine over a period of 30 min. Adult or fetal blood and tissue samples were obtained either at the end of the infusion or 6 h postinfusion for analysis of benzoylecgonine and other cocaine metabolite concentrations via gas chromatography/mass spectrometry (GC/MS). Pregnancy altered benzoylecgonine pharmacokinetics. At the end of the infusion, benzoylecgonine concentration in the fetal plasma was markedly lower than in the maternal plasma with a fetal/maternal ratio of 0.14+/-0.01. A significantly lower concentration of benzoylecgonine was found in both maternal and fetal brain at 0 h postinfusion, with tissue/plasma concentration ratios of 0.04 and 0.24, respectively, suggesting that benzoylecgonine does not readily penetrate into the brain. At 6 h, the fetal concentration of benzoylecgonine was significantly higher than in the corresponding maternal blood and tissues. Ecgonine methyl ester, a metabolite of benzoylecgonine was found in the maternal liver, but not in the fetus. In addition, the amniotic fluid concentration of benzoylecgonine became significantly higher in the 6-h postinfusion samples as compared to the end of infusion value, suggesting that repeated intrauterine exposure to cocaine may cause an accumulation of benzoylecgonine in the fetus.

Understanding drug testing in the neonate and the role of meconium analysis

The use of illicit drugs during pregnancy is a problem that affects a significant number of pregnant women or women of childbearing age. For many reasons, the identification of the drug exposed mother and her infant is a necessary, albeit difficult, task. This article will discuss drug testing to detect the antenatal exposure of the newborn infant to illicit drugs and review the different laboratory methods that are used and the role of meconium analysis in neonatal drug testing.

Long-term intravenous perinatal cocaine exposure on the mortality of rat offspring

To examine the effects of chronic perinatal cocaine exposure, cocaine was administered intravenously throughout pregnancy and the postpartum period to the rat. Pregnant rats were divided into five groups: nontreated (naive); normal saline control (saline); cocaine first generation (cocaine); saline in the first generation and cocaine in the second generation (Sal-2G); and cocaine in both first and second generations (Coc-2G). The rats receiving cocaine in the second generation (Sal-2G and Coc-2G) were offspring of the saline and cocaine group, respectively. All cocaine-treated groups received cocaine 2 mg/kg/day intravenously (IV), and the saline group received normal saline 0.2 ml/day IV from GD 2 to the 21st day postpartum. Mean perinatal mortality was greater in all pups exposed to cocaine in utero during gestation; Cocaine (6.4%); Sal-2G (5.6%); Coc-2G (11.4%) groups than in the noncocaine groups (3.2%, 1.3%). Weight gain, physical, and neurological developments of the offspring were not affected. It was concluded that perinatal cocaine exposure had an increased perinatal mortality even at doses approximately 10 times lower than those previously reported, which were administered by extravascular routes. These findings indicate the importance of the route of drug administration in perinatal cocaine research.

Distribution of cocaine and metabolites in the pregnant rat and fetus in a chronic subcutaneous injection model

We examined the distribution of cocaine and its metabolites benzoylecgonine (BE) and norcocaine (NOR) in pregnant Sprague-Dawley rats and fetuses following twice-daily subcutaneous (s.c.) injections of 20 mg/kg cocaine HCl from gestational day (GD) 8 through GD 20. On GD 21, the animals received a single injection and maternal trunk blood, fetal blood, fetal brains, and amniotic fluid were collected 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, 8 h, or 12 h later for cocaine and metabolite analyses by high-performance liquid chromatography (HPLC) with UV detection. The highest concentrations of cocaine and BE were detected in maternal plasma at 1 h and 4 h respectively. Cocaine peaked at 2 h and BE at 4 h in both fetal plasma and brain. In amniotic fluid, cocaine levels peaked at 2 h, but the highest BE levels were found at 8 h postinjection. An additional group of chronically treated dams was given both cocaine injections on GD 21 and sacrificed 2 h later. Benzoylecgonine concentrations were increased in fetal plasma, fetal brain, and amniotic fluid when compared with the 2-h results following a single cocaine treatment. Moreover, NOR, which had not been previously detected, was now measurable in the amniotic fluid.

Transplacental cocaine exposure. 1: A rodent model

To characterize the transplacental effects of cocaine on the developing brain, we have developed a mouse model of gestational cocaine exposure. Pharmacokinetic analysis revealed that cocaine and its metabolites (BE, BNE, and NC) were found in fetal brain and plasma at 30 and 120 min following SC administration to embryonic day (E) 17 pregnant Swiss Webster mice. Pregnant dams injected twice daily with cocaine HCl at 20 mg/kg SC from gestational day E8 to E17 (COC) demonstrated less food intake and lower percentage weight gain than vehicle-injected dams allowed access to food ad lib (SAL). A nutritionally paired control group of dams injected with saline vehicle and pair-fed with the COC dams (SPF) demonstrated the lowest percentage weight gain of all three groups. The surrogate fostered offspring of COC and SPF dams demonstrated persistent growth retardation [on postnatal days (P) 1, P9, and P50] and transient brain growth retardation (on P1 and P9) when compared to pups born to SAL dams. We conducted behavioral tests that allowed us to dissociate the indirect effect of cocaine-induced malnutrition from a direct effect of prenatal cocaine administration in altering postnatal behavior. Pups from all three groups were tested for first-order Pavlovian conditioning on P9 or P12, or for the ability to ignore redundant information in a blocking paradigm on P50 or P100. Unlike the SPF and SAL controls, COC mice (i.e., mice born to COC dams) were unable to acquire an aversion to an odor previously paired with shock on P9. This learning deficit was transient because on P12, COC mice trained on the same conditioning task displayed an aversion to the odor that was indistinguishable from the SPF and SAL controls. P50 and P100 COC mice (and to a lesser extent, SPF mice) demonstrated a persistent behavioral deficit in the blocking paradigm, which may reflect alterations in selective attention. We discuss how these findings in our rodent model have developmental implications for human infants exposed to cocaine in utero.

Transplacental cocaine exposure. 3: Mechanisms underlying altered brain development

In a mouse model of transplacental cocaine exposure we have demonstrated alterations in brain structure and function of offspring including disturbances of brain growth, disruption of neocortical cytoarchitecture, and transient as well as persistent behavioral deficits. One mechanism by which cocaine may alter fetal brain development is through cocaine-induced alpha-adrenergic-mediated (uterine) arterial vasoconstriction. In this study pregnant Swiss Webster (SW) mice were injected with cocaine HCl (20 or 40 mg/kg, SC) without any changes evident in mean arterial blood pressure (MAP) measurements. These physiology results suggest that in our mouse model, cocaine's transplacental effects on the fetus are not due to cocaine-induced maternal vasoconstriction, nor concomitant hypoperfusion of the fetus. In a separate series of experiments, pregnant SW dams were administered cocaine HCl at 40 mg/kg/day (COC 40), 20 mg/kg/day (COC 20), or 10 mg/kg/day (COC 10) [SC, divided in two daily doses, from embryonic day (E) 8 to E17 inclusive]. Additional groups of cocaine-treated dams were administered phentolamine (5 mg/kg, SC), a short-acting alpha-adrenergic antagonist, 15 min prior to each cocaine dose (Phent COC 40, Phent COC 20, Phent COC 10). Animals born to Phent COC 40 dams demonstrated transient postnatal brain growth retardation and behavioral deficits in first-order conditioning of P9 mice comparable to mice born to COC 40 dams, which received the same regimen of cocaine injections without phentolamine pretreatment. Like COC 40 offspring, Phent COC 40 offspring also demonstrated a persistent deficit in the blocking paradigm. The behavioral and growth findings confirm and extend the physiology data, and imply that in our rodent model, alpha-adrenergic mechanisms (including maternal vasoconstriction) are unlikely to mediate these toxic effects of transplacental cocaine exposure on developing brain.

Natural inhibitors of cholinesterases: implications for adverse drug reactions

PURPOSE

Acetylcholinesterase and butyrylcholinesterase are two closely related enzymes important in the metabolism of acetylcholine and anaesthetic drugs, including succinylcholine, mivacurium, and cocaine. The solanaceous glycoalkaloids (SGAs) are naturally occurring steroids in potatoes and related plants that inhibit both acetylcholinesterase and butyrylcholinesterase. There are many clinical examples of direct SGA toxicity due to cholinesterase inhibition. The aim of this study was to review the hypotheses that (1) SGAs may be the evolutionary driving force for atypical butyrylcholinesterase alleles and that (2) SGAs may adversely influence the actions of anaesthetic drugs that are metabolized by acetylcholinesterase and butyrylcholinesterase.

SOURCE

The information was obtained by Medline search and consultation with experts in the study of SGAs and cholinesterases.

PRINCIPAL FINDINGS

The SGAs inhibit both acetylcholinesterase and butyrylcholinesterase in numerous in vitro and in vivo experiments. Although accurate assays of SGA levels are difficult, published data indicate human serum SGA concentrations at least ten-fold lower than required to inhibit acetylcholinesterase and butyrylcholinesterase in vitro. However, we review evidence that suggests the dietary ingestion of SGAs can initiate a cholinergic syndrome in humans. This syndrome appears to occur at SGA levels lower than those which interfere with anaesthetic drug catabolism. The world distribution of solanaceous plants parallels the distribution of atypical alleles of butyrylcholinesterase and may explain the genetic diversity of the butyrylcholinesterase gene.

CONCLUSION

Correlative evidence suggests that dietary SGAs may be the driving force for atypical butyrylcholinesterase alleles. In addition, SGAs may influence the metabolism of anaesthetic drugs and this hypothesis warrants experimental investigation.

Neurologic and ophthalmologic findings in children exposed to cocaine in utero

We studied a cohort of 73 children exposed to cocaine in utero to characterize the spectrum of neurologic and ophthalmologic abnormalities; 36 children with no documented in utero drug exposure were selected as a control group. Most referrals of cocaine-exposed children to the child neurologist were made in the 1st year of life (81%). Reasons for referral were hypertonia (29%), seizures (22%), developmental delay (11%), tremulousness (11%), and hypotonia (4%). The most common abnormal finding in the cocaine-exposed children was hypertonia/hyperreflexia (63%), which was rarely seen in the control group. In addition, hypertonia/hyperreflexia was underdiagnosed by referring physicians. Similarly, hypotonia was seen on neurologic examination of cocaine-exposed children more frequently than documented by referral (16% versus 4%). Hypotonia was rarely seen in the control group. Twelve (43%) of 28 cocaine-exposed children seen by a pediatric ophthalmologist had structural ophthalmologic abnormalities. Neurologic and ophthalmologic findings suggesting structural lesions of the nervous system must be considered in cocaine-exposed children.