Risks to the infant
What is currently known about the influence of venlafaxine on breastfeeding and its impact on the baby rests in little information, not based on randomized controlled trials but in some cases studies, so any statement is made considering the inadequacy of the information available and the caution needed in these cases. Very little is known of venlafaxine and other antidepressants regarding to breastfeeding .
No adverse effects have been reported in infants as a result of the administration of venlafaxine to mothers. One study estimated the average dose ingested by infants was 7.6% of the maternal dose adjusted by weight. Were not found influences on children, although the authors draw attention to how high this dose is compared with that received by other SSRI antidepressants through milk. Hendrick et al report that in the children of two female infants treated with 75 and 150 mg of venlafaxine respectively at 3 and 4 weeks did not detect any amount of drug in the blood, while did find concentrations of O-desmethylvenlafaxine 16 and 21 ng / ml, respectively. In three infants aged between 2 weeks and six months, whose mothers received venlafaxine at doses between 3 and 8 mg / kg, the drug was undetectable in plasma, while the O-desmethylvenlafaxine blood values ??reached between 23 and 225 ng / ml. In none of these five cases were recorded implication for infants.
In three breastfed infants of less than six months of age whose mothers took from 75 to 225 mg of venlafaxine levels were found in 10.2% of the concentration of the mothers, mostly in the form of O-desmethyl derivative . Other preliminary data show that the amount ingested by infants can reach 9.2% of the maternal dose.
Another three cases of infants exposed to the drug for six months through breast milk, whose mothers took an average dose of 162.5 mg / day, showed normal weight . In a study of seven cases of infants between 3 and 10 months, the Denver test was normal. Five of the seven infants showed normal development and in the other two showed a decrease in weight gain. 
In summary, it is know a total of about 18 infants whose mothers took venlafaxine during lactation. Except as said the preceding paragraph, there were no adverse effects of the drug on children. In cases studied, levels of venlafaxine, O-desmethylvenlafaxine or both, the concentrations can reach 2.5 and 2.7 times those in maternal plasma. The drug exposure varies between 6.4% and 10.2% of the dose given to the mother, a percentage close to the level that is generally considered of concern (10%), unlike other SSRI antidepressants that are undetectable in infants .
Exposure to antidepressants through breast milk does not seem to affect the child's weight. However, infants exposed to maternal depression for two or more months seem to experience less weight gain statistically significant that euthymic female infants or mothers experiencing depressive episode during an interval of shorter duration .
Influence on lactation
Case data on the possible influence of the drug on lactation are very limited. It has reported a case of milk secretion decreased one month after initiation of treatment with venlafaxine. 
Levels of venlafaxine and its active metabolite peaked milk value between one and three hours after dosing in two of three women. . In five other women found similar results; venlafaxine peak was reached between 1.7 and 2.8 hours, while for the active metabolite are reached somewhat later (1.8-4.2 hours). The slow release form did average at 5.7 and 7.7 hours after dosing respectively for the preparation of venlafaxine or its O-desmethyl derivative .
Venlafaxine can increase prolactin. It have reported three cases of galactorrhea associated with the administration of the drug, although it is unknown the possible importance of this on the nursing woman. As in the case of other enhancers of prolactin, the final effect on breastfeeding is very low if exists. Probably, have not been posted any negative impact on breastfeeding by this reason.
Venlafaxine is considered not incompatible with breastfeeding, but the children of mother receiving this antidepressant should be followed carefully, especially newborns and preterm infants, monitoring for possible excessive sedation and checking that the infant undergoes adequate weight gain.
Although not a routine clinical method, the determination of the active metabolite of venlafaxine, O-desmethylvenlafaxine, can serve as a guide in selected cases. Given the lack of information about this medicine, it is preferable to starting antidepressant treatment with another substance. For some authors, the drugs of choice could be nortriptyline, paroxetine or sertraline.
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3. Ilett KF, Hackett LP, Dusci LJ, Roberts MJ, Kristensen JH, Paech M, Groves A,Yapp P. Distribution and excretion of venlafaxine and O-desmethylvenlafaxine in human milk. Br J Clin Pharmacol. 1998 May;45(5):459-62.
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6. Ilett KF, Kristensen JH, Hackett LP, Paech M, Kohan R, Rampono J. Distribution of venlafaxine and its O-desmethyl metabolite in human milk and their effects in breastfed infants. Br J Clin Pharmacol. 2002 Jan;53(1):17-22.
7. Pae CU, Kim JJ, Lee CU et al. Very low dose quetiapine-induced galactorrhea in combination with venlafaxine. Hum Psychopharmacol. 2004;19:433-4.
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10. American Academy of Pediatrics. Committee on Drugs. The transfer of drugs and other chemicals into human milk. Pediatrics. 2001;108:776-89.
Warning of the manufacturer:
Do not use during lactation.