Physiologically-Based Pharmacokinetic Modeling to Investigate the Effect of Maturation on Buprenorphine Pharmacokinetics in Newborns with Neonatal Opioid Withdrawal Syndrome.

Neonatal opioid withdrawal syndrome (NOWS) is a major public health concern whose incidence has paralleled the opioid epidemic in the United States. Sublingual buprenorphine is an emerging treatment for NOWS, but given concerns about long-term adverse effects of perinatal opioid exposure, precision dosing of buprenorphine is needed. Buprenorphine pharmacokinetics (PK) in newborns, however, is highly variable. To evaluate underlying sources of PK variability, a neonatal physiologically-based pharmacokinetic (PBPK) model of sublingual buprenorphine was developed using Simcyp (version 19.1). The PBPK model included metabolism by cytochrome P450 (CYP) 3A4, CYP2C8, UDP-glucuronosyltransferase (UGT) 1A1, UGT1A3, UGT2B7, and UGT2B17, with additional biliary excretion. Maturation of metabolizing enzymes was incorporated, and default CYP2C8 and UGT2B7 ontogeny profiles were updated according to recent literature. A biliary clearance developmental profile was outlined using clinical data from neonates receiving sublingual buprenorphine as NOWS treatment. Extensive PBPK model validation in adults demonstrated good predictability, with geometric mean (95% confidence interval (CI)) predicted/observed ratios (P/O ratios) of area under the curve from zero to infinity (AUC0-∞ ), peak concentration (Cmax ), and time to reach peak concentration (Tmax ) equaling 1.00 (0.74-1.33), 1.04 (0.84-1.29), and 0.95 (0.72-1.26), respectively. In neonates, the geometric mean (95% CI) P/O ratio of whole blood concentrations was 0.75 (95% CI 0.64-0.87). PBPK modeling and simulation demonstrated that variability in biliary clearance, sublingual absorption, and CYP3A4 abundance are likely important drivers of buprenorphine PK variability in neonates. The PBPK model could be used to guide development of improved buprenorphine starting dose regimens for the treatment of NOWS.

Stereoselective Analysis of Methadone and EDDP in Laboring Women and Neonates in Plasma and Dried Blood Spots and Association with Neonatal Abstinence Syndrome.

OBJECTIVE: This pilot study evaluated the relationship between maternal and neonatal R- and S-methadone and R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) exposure and the severity of neonatal abstinence syndrome (NAS). The use of dried blood spots (DBS) as an alternative for plasma in assessing methadone and EDDP was also assessed. STUDY DESIGN: Women receiving methadone for medication assisted treatment of opioid use disorder during pregnancy were eligible for recruitment. Plasma and DBS samples were collected from mothers during labor, from cord blood, and from newborns during genetic screen. R-/S-methadone and EDDP were measured by high-performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS). Associations between methadone exposure, neonatal morphine requirements, and severity of NAS were examined. RESULTS: Twenty women and infants completed the study. Maternal methadone dose at delivery was 112 mg/day (range = 60-180 mg/day). Sixteen neonates experienced NAS requiring morphine; three also required phenobarbital. Higher cord blood concentrations of R-methadone, R- and S-EDDP were associated with higher maximum doses of morphine (p < 0.05). CONCLUSION: Maternal methadone and cord blood concentration at delivery are variable and may be potential markers of neonatal abstinence syndrome.

The evaluation of lymphopenia in infants exposed to opioids in-utero.

BACKGROUND: Chronic use of opioids is associated with hematologic and immunologic effects, including lymphopenia. Despite an increase in opioid use during pregnancy, little is known about the potential immunologic effects on the neonate after exposure to opioids in-utero. We aimed to evaluate the presence of lymphopenia among neonates exposed to opioids in-utero. METHODS: We conducted a retrospective chart review of infants admitted to the neonatal intensive care unit (NICU) of a single institution after exposure to opioids in-utero. We compared the lymphocyte counts of this population to a control NICU population. RESULTS: A higher percentage of neonates exposed to opioids in-utero were lymphopenic compared to our control population (44% vs 24%, p = 0.035). CONCLUSIONS: This is the first study we are aware of, that investigated an association between neonatal lymphopenia and opioid exposure in-utero. Further studies to explore clinical implications of this finding are needed.

Validation of a HPLC/MS method for simultaneous quantification of clonidine, morphine and its metabolites in human plasma.

A high-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of morphine, morphine's major metabolites morphine-3-glucuronide and morphine-6-glucuronide, and clonidine, to support the pharmacokinetic analysis of an ongoing double-blinded randomized clinical trial that compares the use of morphine and clonidine in infants diagnosed with neonatal abstinence syndrome. Plasma samples were processed by solid-phase extraction and separated on an Inertsil ODS-3 (4 µm) column using an 0.1% formic acid in water-0.1% formic acid in methanol gradient. Detection of the analytes was conducted in the positive multiple reaction monitoring mode. The range of quantitation was 1-1000 ng/mL for morphine, morphine-3-glucuronide and morphine-6-glucuronide, and 0.25-100 ng/mL for clonidine. Intra-day and inter-day accuracy and precision were ≤15% for all analytes across the quantitation range. Extraction recovery rates were ≥94% for morphine, ≥90% for M3G, ≥87% for M6G and ≥ 79% for clonidine. Matrix effect ranged from 85-94% for clonidine to 101-106% for M3G. The method fulfilled all predetermined acceptance criteria and required only 100 µL of starting plasma volume. Furthermore, it was successfully applied to 30 clinical trial plasma samples.

Methadone dosing strategies in preterm neonates can be simplified.

AIMS: A dramatic increase in newborn infants with neonatal abstinence syndrome has been observed and these neonates are frequently treated with complex methadone dosing schemes to control their withdrawal symptoms. Despite its abundant use, hardly any data on the pharmacokinetics (PK) of methadone is available in preterm neonates. Therefore we investigated developmental PK of methadone and evaluated current dosing strategies and possible simplification in this vulnerable population. METHODS: A single-centre open-label prospective study was performed to collect PK data after a single oral dose of methadone in preterm neonates. A population PK model was built to characterize developmental PK of (R)- and (S)-methadone. Model-based simulations were performed to identify a simplified dosing strategy to reach and maintain target methadone exposure. RESULTS: A total of 121 methadone concentrations were collected from 31 preterm neonates. A one-compartment model with first order absorption and elimination kinetics best described PK data for (R)- and (S)-methadone. Clearance increases with advancing gestational age and differs between R- and S-enantiomer, being slightly higher for the former (0.244 vs 0.167 L/h). Preterm neonates reached target exposure after 48 hours with currently used dosing schedules. Output from simulations revealed that target exposures can be achieved with a simplified dosing strategy during the first 4 days of treatment. CONCLUSION: Methadone clearance in preterm neonates increases with advancing gestational age and its disposition is influenced by its chirality. Simulations that account for developmental PK changes indicate a shorter methadone dosing strategy can maintain target exposure to control withdrawal symptoms.

In Utero Oxcarbazepine Exposure and Neonatal Abstinence Syndrome: Case Report and Brief Review of the Literature.

Oxcarbazepine is a second-generation antiepileptic drug that is used to treat partial seizures. Although it has been increasingly used in pregnant women, its fetal safety has not been fully validated. We describe a 12-hour-old neonate who developed neonatal abstinence syndrome (NAS) after intrauterine exposure to oxcarbazepine. The neonate was born via cesarean section to a mother who took oxcarbazepine 300 mg/day for treatment of seizures throughout her pregnancy. Approximately 12 hours after birth, the infant developed paroxysmal jitter, which mainly presented as increased excitability, irritability, limb shaking, and increased muscle tone. These symptoms resolved by day 9 of life. Although NAS occurs most often after in utero exposure to opioids, exposure to other drugs during pregnancy may contribute to a small proportion of NAS cases. To our knowledge, this is the second case report of oxcarbazepine-induced NAS. Pregnant women with epilepsy should weigh the pros and cons of continuing oxcarbazepine during their pregnancy when they are prescribed this drug. For infants with in utero oxcarbazepine exposure, comprehensive assessments and examinations are necessary for screening oxcarbazepine-induced NAS.

Pharmacokinetics and Pharmacogenetics of Selective Serotonin Reuptake Inhibitors During Pregnancy: An Observational Study.

BACKGROUND: An involvement of selective serotonin reuptake inhibitors (SSRIs) in increasing the risk of malformations, neonatal withdrawal syndrome, has been suggested recently. Here, we aimed to investigate the contribution of individual pharmacogenetics of SSRI on infants' outcome. We also estimated the umbilical/maternal plasma SSRI concentration ratio in the pregnant women still on SSRI therapy at the time of delivery. METHODS: Thirty-four pregnant women, referred to our hospital from January 2011 to July 2015, who were given SSRIs in the third trimester, and related children, were considered. The umbilical/maternal plasma SSRI concentration ratio was estimated in 15 mothers still on SSRI therapy at the time of delivery. For patients with pharmacokinetic analyses, blood samples were collected for pharmacogenetic analyses. RESULTS: Nineteen newborns presented clinical signs possibly related to drug toxicity. A high umbilical/maternal plasma ratio of SSRI was observed in 10 of the 15 evaluated newborns. Five mothers were intermediate metabolizers and 1 a poor metabolizer for the major CYP enzyme involved in pharmacokinetic pathway. CONCLUSIONS: Individualized psychopharmacologic treatment that takes into account the mother's exposure to SSRI concentrations and eventually her genetic background may become the standard of care to maximize drug benefit and minimize risks to the newborn.

Skin conductance in neonates suffering from abstinence syndrome and unexposed newborns.

UNLABELLED: The aims of this study were to compare the skin conductance (SC) of newborns with opiate-induced neonatal abstinence syndrome (NAS) to that of unexposed newborns and to evaluate the potential of SC readings to detect distress in the context of NAS objectively. The SC of 12 newborns with NAS and 12 unexposed newborns was measured at nine specific times during their first 6 weeks of life. The number of SC fluctuations per second (NSCF/s), the amplitude of SC fluctuation, and the mean level of SC were recorded and analyzed. The SC of newborns treated for symptoms of NAS differed significantly from the SC of unexposed newborns with regard to the NSCF/s (p = 0.04). With the mean level of SC, we observed an interaction between groups over time (p value for interaction = 0.02). With increasing postnatal age, we observed higher values in all three SC parameters. CONCLUSION: The NSCF/s and the mean level of SC appear to be suitable to reflect the distress of newborns suffering from NAS. As it is known that the sensitivity of SC increases with the level of stress experienced, its potential to indicate elevated stress levels in infants with NAS should be investigated in future studies evaluating different therapy regimens. WHAT IS KNOWN: • Skin conductance is a result of the filling of palmar and plantar sweat glands innervated by the sympathetic nervous system • Skin conductance can be used as a measure of stress and pain in newborns What is New: • Skin conductance of newborns with neonatal abstinence syndrome (NAS) differs significantly from the SC of non-substance-exposed newborns during the first 6 weeks of life • Skin conductance appears to reflect the increased distress of infants with NAS.

Mechanistic Population Pharmacokinetics of Morphine in Neonates With Abstinence Syndrome After Oral Administration of Diluted Tincture of Opium.

Conducting and analyzing clinical trials in vulnerable neonates are extremely challenging. The aim of this analysis is to develop a morphine population pharmacokinetics (PK) model using data collected during a randomized control trial in neonates with abstinence syndrome (NAS). A 3-compartment morphine structural PK model after intravenous (IV) administration from previously published work was utilized as prior, whereas an allometric scaling method with physiological consideration was used to extrapolate a PK profile from adults to pediatrics. The absorption rate constant and bioavailability were estimated in NAS after oral administration of diluted tincture of opium (DTO). Goodness-of-fit plots along with normalized prediction distribution error and bootstrap method were performed for model evaluation. We successfully extrapolated the PK profile from adults to pediatrics after IV administration. The estimated first-order absorption rate constant and bioavailability were 0.751 hour(-1) and 48.5%, respectively. Model evaluations showed that the model can accurately and precisely describe the observed data. The population pharmacokinetic model we derived for morphine after oral administration of DTO is reasonable and acceptable; therefore, it can be used to describe the PK and guide future studies. The integration of the previous population PK knowledge as prior information successfully overcomes the logistic and practical issue in vulnerable neonate population.

Opioids in pregnancy and neonatal abstinence syndrome.

Opiate use in pregnancy has increased dramatically over the past decade and now represents a major public health problem. More women are using prescription opioids, illegal opioids, and opioid-substitution therapy. These drugs have been associated with numerous obstetrical complications including intrauterine growth restriction, placental abruption, preterm delivery, oligohydramnios, stillbirth, and maternal death. Neonatal complications are also significant, such as an increased risk of mortality as well as neonatal abstinence syndrome (NAS). NAS is a serious and highly variable condition characterized by central nervous system hyperirritability and autonomic nervous system dysfunction. The present review seeks to define current practices regarding the management of opiate dependence in pregnancy and care of the neonate with prenatal opiate exposure. Since genetic factors appear to be associated with the incidence and severity of NAS, opportunities for "personalized genomic medicine" and unique therapeutic interventions could be developed in the future.

Genetic determinants of fetal opiate exposure and risk of neonatal abstinence syndrome: Knowledge deficits and prospects for future research.

Opiate-dependent pregnant women receive opiate maintenance medications to prevent illicit use and withdrawal. Fetal opiate exposure causes central nervous system (CNS) alterations which manifest as postnatal physical withdrawal. The extensive variability in the Neonatal Abstinence Syndrome phenotype remains unexplained and may be related to variability in fetal exposure and response. Improved understanding of functionally significant genetic variants in pathways influencing placental opiate transfer and fetal response can lead to personalized maternal therapy and optimized neonatal outcomes.

Evidence-based nurse-driven interventions for the care of newborns with neonatal abstinence syndrome.

Neonatal abstinence syndrome (NAS) is a growing problem in the United States, related to increased maternal substance use and abuse, and a set of drug withdrawal symptoms that can affect the central nervous system and gastrointestinal and respiratory systems in the newborn when separated from the placenta at birth. Infants with NAS often require a significant length of stay in the neonatal intensive care unit (NICU). Pharmacologic treatments and physician-directed interventions are well researched, but nursing-specific interventions and recommendations are lacking. A thorough review and analysis of the literature and interviews with neonatal experts guided the development of a nursing clinical practice guideline for infants with NAS in a level IV NICU. Recommended nursing-specific interventions include methods for maternal drug-use identification, initiation and timing of the Finnegan Scoring System to monitor withdrawal symptoms, and bedside interventions to lessen the drug-withdrawal symptoms in the newborn with NAS.

Neonatal toxicity following maternal citalopram treatment.

Late gestational exposure to citalopram, may be associated with a neonatal toxicity syndrome with immediate onset at birth or soon after birth and sometimes may be mistaken for neonatal withdrawal syndrome. A 3860 g infant was delivered at 40 weeks gestation. The mother had been taking citalopram 20 mg/day until the day of delivery. Fifteen minutes after birth, the baby became hypertonic. Neonatal serotonin toxicity due to citalopram seems the most likely mechanism, though an important differential diagnosis is a citalopram withdrawal syndrome. We suggest the hypothesis that neonatal withdrawal syndrome may follow citalopram serotonin toxicity.

Infants born to mothers under phenobarbital treatment: correlation between serum levels and clinical features of neonates.

OBJECTIVE: Phenobarbital crosses the placenta quickly, and the balance between maternal and fetal blood is achieved in a few minutes. Data on the clinical outcomes of infants born to mothers under phenobarbital treatment during pregnancy show that they are at risk of adverse events, such as sedation and abstinence syndrome. The aim of this study was to analyse the correlation between serum levels of phenobarbital and clinical features of neonates. STUDY DESIGN: Twenty-three infants born between 2001 and 2008 were studied. Maternal, neonatal and pharmacological variables were considered. RESULTS: Eleven infants displayed symptoms related to phenobarbital. Withdrawal syndrome was seen in seven infants and sedation syndrome was seen in four infants. One infant had severe cardiorespiratory depression at birth. None of the infants had severe neonatal abstinence syndrome. No statistically significant differences were found between symptomatic and asymptomatic infants. At birth, the mean serum level of phenobarbital of the 23 infants was 15.4 [standard deviation (SD) 6.2] µg/ml. A peak (16.1 µg/ml, SD 5.5) was seen on Day 3, followed by a gradual decrease to non-therapeutic levels (<10 µg/ml) by Day 8 (9.3 µg/ml, SD 1.0). Phenobarbital levels were higher in symptomatic infants than asymptomatic infants, although the difference was not statistically significant. CONCLUSIONS: Serum levels of phenobarbital remained in the therapeutic range for both mothers and infants, and reduced gradually in infants. However, some infants displayed symptoms related to phenobarbital. As such, a clinical pharmacological surveillance protocol is necessary.

Clonidine clearance matures rapidly during the early postnatal period: a population pharmacokinetic analysis in newborns with neonatal abstinence syndrome.

The population pharmacokinetic (PK) profile of oral clonidine was characterized in newborns with neonatal abstinence syndrome, and significant covariates affecting its PK parameters were identified. Plasma clonidine concentration data were obtained from a clinical trial in which 36 newborns, aged 1 to 25 days (postnatal age, PNA) and weighing 2.1 to 3.9 kg, were enrolled to take multiple oral doses of clonidine. The population PK model of clonidine was developed by NONMEM, and significant covariates were identified, followed by nonparametric bootstraps (2000 replicates) and simulation experiments. A 1-compartment open linear PK model was chosen to describe plasma concentrations of clonidine, and body weight and PNA were significant covariates for apparent clearance (CL/F) as follows: CL/F (L/h) = 15.2 × [body weight (kg)/70](0.75) × [PNA (day)(0.441)/(4.06(0.441) + PNA (day)(0.441))]. Furthermore, CL/F of clonidine increased rapidly with PNA during the first month of life after body weight was adjusted. Any optimal dosage regimen for clonidine in term neonates should be based on infant's age and body weight, and 1.5 µg/kg every 4 hours is proposed starting the second week of life based on the simulation results.

Sublingual buprenorphine for treatment of neonatal abstinence syndrome: a randomized trial.

OBJECTIVE: In utero exposure to drugs of abuse can lead to neonatal abstinence syndrome, a condition that is associated with prolonged hospitalization. Buprenorphine is a partial mu-opioid agonist used for treatment of adult detoxification and maintenance but has never been administered to neonates with opioid abstinence syndrome. The primary objective of this study was to demonstrate the feasibility and, to the extent possible in this size of study, the safety of sublingual buprenorphine in the treatment of neonatal abstinence syndrome. Secondary goals were to evaluate efficacy relative to standard therapy and to characterize buprenorphine pharmacokinetics when sublingually administered. METHODS: We conducted a randomized, open-label, active-control study of sublingual buprenorphine for the treatment of opiate withdrawal. Thirteen term infants were allocated to receive sublingual buprenorphine 13.2 to 39.0 mug/kg per day administered in 3 divided doses and 13 to receive standard-of-care oral neonatal opium solution. Dose decisions were made by using a modified Finnegan scoring system. RESULTS: Sublingual buprenorphine was largely effective in controlling neonatal abstinence syndrome. Greater than 98% of plasma concentrations ranged from undetectable to approximately 0.60 ng/mL, which is less than needed to control abstinence symptoms in adults. The ratio of buprenorphine to norbuprenorphine was larger than that seen in adults, suggesting a relative impairment of N-dealkylation. Three infants who received buprenorphine and 1 infant who received standard of care reached protocol-specified maximum doses and required adjuvant therapy with phenobarbital. The mean length of treatment for those in the neonatal-opium-solution group was 32 compared with 22 days for the buprenorphine group. The mean length of stay for the neonatal-opium-solution group was 38 days compared with 27 days for those in the buprenorphine group. Treatment with buprenorphine was well tolerated. CONCLUSIONS: Buprenorphine administered via the sublingual route is feasible and apparently safe and may represent a novel treatment for neonatal abstinence syndrome.

Paroxetine toxicity in a newborn after in utero exposure: clinical symptoms correlate with serum levels.

There are several case reports and case series that have examined the acute effects of selective serotonin reuptake inhibitors (SSRIs) on the newborn. There is considerable controversy whether the reported symptoms represent withdrawal from the SSRI or toxicity caused by the SSRI. A case of an infant who was exposed to paroxetine during pregnancy is presented. This case supports the notion of serotonin toxicity and is believed to be the first report that substantiates clinical symptoms with serum levels of the offending SSRI.

Can methadone concentrations predict the severity of withdrawal in infants at risk of neonatal abstinence syndrome?

AIM: To assess the usefulness of cord and serum methadone concentrations at 2 days of age in predicting the severity of neonatal abstinence syndrome (NAS) in infants whose mothers received methadone during pregnancy. METHODS: After informed consent, infants were enrolled if they were delivered at 35 weeks gestation or greater. Relevant information was collected from maternal notes. A sample of cord blood was taken at delivery, with a follow up sample at 48 hours of age. The samples were analysed in batches, and the results were unavailable to the attending clinical staff. Infants were treated for NAS on clinical grounds according to a standardised scoring system. RESULTS: Twenty five of 36 eligible infants over the 21 month period of the study were enrolled. Of these, 12 required treatment for NAS. Maternal methadone dose did not predict the need for treatment. However, infants who required treatment had significantly lower methadone concentrations in cord blood than the group who did not receive treatment (31 v 88 ng/ml respectively; p = 0.029). Paired blood samples for methadone concentrations were available for 17 infants. All but one of the 12 infants who required treatment had undetectable concentrations of methadone in the postnatal sample, whereas the median postnatal methadone concentration in untreated infants was 23 ng/ml (p = 0.002). CONCLUSIONS: Methadone concentrations taken from cord blood may identify infants at greater risk of neonatal withdrawal and therefore requiring treatment.

Pharmacologic factors associated with transient neonatal symptoms following prenatal psychotropic medication exposure.

BACKGROUND: Selective serotonin reuptake inhibitor antidepressants (SSRIs) and benzodiazepines are frequently used to treat maternal depression and anxiety disorders during pregnancy. Recent reports suggest that prenatal SSRI exposure is associated with a neonatal discontinuation syndrome. It remains unclear whether these symptoms are directly related to SSRI exposure alone or are due to concurrent pharmacologic factors. Also, this study explores relationships between neonatal outcomes and medication levels during pregnancy, at delivery, and in the newborn period. METHOD: This study sought to compare newborn behavior following second and third trimester exposure to either single-agent SSRIs (group 1) or SSRIs combined with clonazepam (group 2). A prospective cohort of mothers and their infants (N = 46) who had received SSRI medication alone or in combination with clonazepam were studied from June 1996 through June 2000 and compared with a nonexposed control group (N = 23). Infants were assessed in the newborn period for signs suggestive of a "discontinuation syndrome." Maternal drug levels were measured during the pregnancy and at delivery. Infant drug levels from cord blood and at day 2 of life were also obtained. RESULTS: Overall, 30% of the exposed infants (groups 1 and 2, N = 14) showed symptoms of transient poor neonatal adaptation compared with 9% (N = 2) of control infants. In group 1, 25% had symptoms (fluoxetine N = 3; paroxetine N = 3; sertraline N = 1) and in group 2, 39% of infants had symptoms (paroxetine with clonazepam, N = 7). Symptoms were typically mild respiratory distress and, less commonly, hypotonia. Symptoms were self limited and not associated with other neonatal conditions. When paroxetine was combined with clonazepam, infants with symptoms had significantly elevated paroxetine levels when compared with similarly exposed infants without symptoms (p <.05). Among single-agent paroxetine-exposed infants, drug levels did not differ significantly between those with and without symptoms. Maternal dose of clonazepam was significantly higher (p <.05) during pregnancy and at delivery among symptomatic infants compared with nonsymptomatic infants. Developmental outcomes at 2 and 8 months of age did not differ between symptomatic and nonsymptomatic infants. CONCLUSION: While transient neonatal symptoms were found in infants after single-agent prenatal exposure to SSRIs and when paroxetine was combined with clonazepam, the addition of clonazepam appeared to alter paroxetine metabolism, leading to increased drug levels and risk for transient neonatal symptoms. These data highlight the importance of accounting for a variety of pharmacologic factors beyond single-agent SSRI exposure that may lead to poor neonatal adaptation. Further studies are needed with a larger sample of infants to determine the role of clonazepam and whether similar outcomes occur when exposure includes other SSRIs in combination with clonazepam.

Neonatal thrombocytosis resulting from the maternal use of non-narcotic antischizophrenic drugs during pregnancy.

Neonatal thrombocytosis can result from maternal narcotic drug abuse. The case of a male infant is reported who was born to a woman with schizophrenia treated with non-narcotic psychotropic drugs during pregnancy; he developed severe prolonged thrombocytosis. The platelet count reached 1310 x 10(9)/l on day 15. This thrombocytosis persisted for three months. The patient was treated with dipyridamole. A bone marrow aspirate showed normal myeloid and erythroid precursors with an increased number of megakaryocytes. Plasma concentrations of interleukin 6 and thrombopoietin were suppressed. No obvious complications from the thrombocytosis occurred, and the platelet count fell to within the upper limit of normal after 3 months of age. This case indicates that thrombocytosis may occur in infants born to mothers treated with non-narcotic psychopharmaceutical drugs during pregnancy. The thrombocytosis in this case may have been induced by factors other than interleukin 6 or thrombopoietin.