Cholinesterases placental

Several centers have been collecting human samples, including urine, breast milk, peripheral blood, cord blood, meconium, vernix, saliva, hair, and placental tissue (Eskenazi et al. 2005). The samples have been analyzed for the presence of numerous substances, such as mercury, lead, cotinine, pesticides, phthalates, PAHs, PAH-DNA adducts, allergens, endotoxin, antioxidant micronutrients, cytokines, immunoglobulin E, cholinesterase, and thyroid hormones. The centers have also been storing samples for future research purposes (Eskenazi et al. 2005). 

Physostigmine is very sluggishly absorbed from the GI-tract. The drug gets hydrolyzed by the enzymes cholinesterases, and is also metabolized in the liver. It is excreted mostly in the urine as its metabolites and partly as unchanged drug. The drug happens to cross the placental barrier and only very small quantum are usually excreted in the breast-milk. However, the penetration into the CNS is comparatively veiy slow. 

From a search of the literature on pesticides and placental toxicokinetics, it is obvious that not much specific infonna-tion is available. Most. studies are on the effects of pesticide administration during pregnancy on experimental animals, mainly rabbits, rats, and mice, in which the fetal outcome and sometimes the presence of residues ttt the fetal tissue.s have been observed (Gupta, 1995). Naturally, if specific effects in the fetus, such as inhibition of cholinesterase or compound-related residues in the fetus and the placenta, have been observed, it is relatively safe to make the conclusion that the pe.sticide has been transferred from the mother to the fetus. Otherwise, very little direct infonnation is available. 

Chloroprocaine (N,N -diethylaminoethyl 4-amino-2-chlorobenzoate) is a very short-acting, amino ester-type local anesthetic used to provide regional anesthesia by infiltration as well as by peripheral and central nerve block, including lumbar and caudal epidural blocks. The presence of a chlorine atom ortho to the carbonyl of the ester function increases its rate of hydrolysis by plasma cholinesterase at least threefold compared to procaine and benzocaine. Thus, chloroprocaine may be used in maternal and neonatal patients with minimal placental passage of chloroprocaine. The lower plasma cholinesterase activity in the maternal epidural space must still have sufficient activity for degrading chloroprocaine and, thus, not allowing it to cross the placenta barrier. 

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