Myoclonic seizures in a preterm baby: is this a presentation of venlafaxine withdrawal?

Pregnancy exposure to venlafaxine-Therapeutic drug monitoring in maternal blood, amniotic fluid and umbilical cord blood and obstetrical outcomes

BACKGROUND

For treatment with psychotropic drugs during pregnancy, extended therapeutic drug monitoring is recommended for individual therapy adjustment. We measured venlafaxine (VEN), O-desmethylvenlafaxine (ODV) and active moiety, AM (sum of VEN+ODV) concentrations in maternal serum, amniotic fluid and umbilical cord blood.

METHODS

Concentrations of VEN, ODVEN and AM were measured in nine mother-infant pairs at time of delivery; in five cases, amniotic fluid samples were available. Concentrations are reported as median values, first (Q1) and third (Q3) quartiles and ranges. Penetration ratio was calculated by dividing concentrations of VEN, ODVEN and AM in amniotic fluid and umbilical cord blood by maternal serum concentrations.

RESULTS

Median daily dosage of venlafaxine was 75 mg (range 37.5-225 mg). There were no significant correlations between daily dose, maternal serum, umbilical cord blood and amniotic fluid concentrations. Median penetration ratio into amniotic fluid was 2.5 (range 0.56-4.48). Median penetration ratio into fetal circulation was 1.05 (range 0.62-2.08). Median concentration of AM was 223.8 ng/mL, range 33.9-338.0 ng/mL (maternal serum), 789.0 ng/mL, range 309-1052.5 ng/mL (amniotic fluid) and 291.0 ng/mL, range 21.1-448.4 ng/mL (cord blood).

DISCUSSION

VEN, ODVEN and AM concentrations in maternal serum, amniotic fluid and umbilical cord blood indicate that the fetus might have been exposed to relatively high concentrations throughout pregnancy. High concentrations in amniotic fluid indicate an increased penetration into and/or accumulation within amniotic fluid and a decreased elimination out of amniotic fluid. Findings indicate that fetal in-utero exposition to venlafaxine is higher compared to other antidepressants.

Neonatal venlafaxine discontinuation syndrome: A mini-review

During pregnancy, the developing fetal brain may be exposed to a range of psychotropic medications. The serotonin-noradrenergic reuptake inhibitor venlafaxine is one such drug, when used as a maternal antidepressant. Here we review the discontinuation phenomenon that may follow in exposed neonates following birth. Adults who abruptly stop taking venlafaxine can experience withdrawal symptoms. Venlafaxine and its metabolites cross the placenta and so the newborn can be exposed to this risk, as well as potential toxicity. Several case reports document features of encephalopathy following birth in exposed neonates. It is suggested that a possible combination of partial toxicity together with withdrawal may lead to these symptoms - a discontinuation syndrome. The underlying neurobiology is not yet established. Common symptoms and signs seen in affected neonates include poor feeding, jitteriness, respiratory distress and myoclonic seizure-like activity. Onset is typically between birth and day 4 of life with resolution by 2-21 days of life. Electroencephalography does not necessarily correlate with clinical seizures, or response to anticonvulsants. In limited follow-up data, no long-term consequences of this discontinuation syndrome are reported. We suggest where it is not possible for mothers to be switched from venlafaxine to other antidepressant drugs, that their infants are observed closely for 2-4 days following delivery. In symptomatic neonates, following exclusion of other causes, supportive care including breastfeeding may be sufficient for management. Clinicians should be vigilant to venlafaxine discontinuation as a cause for encephalopathy or paroxysmal episodes in exposed neonates.