Breast pumping and lactational state exert differential effects on ethanol pharmacokinetics

Abstract

Prior research revealed that breast stimulation altered the way the lactating body handles alcohol. Its effects depended upon when it occurred relative to drinking. The goal of the present study was to determine whether breast pumping works independently of the physiological and metabolic changes that accompany lactation. To this end, we tested 12 women when they were exclusively breastfeeding 3-5-month-old infants and then again several months after lactation had ceased. Subjects were randomly assigned to one of two groups that differed in the timing of breast pumping relative to drinking a 0.4g/kg dose of alcohol: one group breast pumped 0.6h after drinking (pumped after group) and the other pumped 1h before drinking (pumped before group). For each reproductive stage, subjects were tested on 2 separate days, consuming a standardized meal 1 h before drinking during 1 test day and remaining fasted during the other. Breath alcohol concentrations (BrAC) and temperature readings were obtained before and at fixed intervals after drinking. Pumping before drinking significantly decreased BrAC during both reproductive stages, whereas pumping after drinking resulted in different BrAC time curves during lactation when compared with after lactation. That is, levels were significantly lower during the descending phase of the time curve during than after lactation. The interactions between pumping and reproductive stage were most apparent during fed condition. Furthermore, women were more sensitive to hypothermic effects of both fasting and drinking alcohol during lactation. These findings add to the growing literature that lactating women metabolize alcohol differently, in part, due to the frequent breast stimulation during breastfeeding and the pronounced physiological changes that accompany one of the most energetically costly mammalian activities.

Figure 1

Schedule of Events. Two groups of women were tested on two days separated by one week at two time periods: during and after lactation. Conditions were the same during both time periods. At time 0, women drank a 0.4 g/kg body weight dose of alcohol following a 12-hour overnight fast during one test session (Fasted Condition) or 1 hr after the consumption of a standard breakfast during the other (Fed Condition). Group PB breast pumped for 16 minutes one hour before circles) whereas Group PA breast pumped for 16 minutes beginning 35 min (0.6 hours) after (triangles) drinking alcohol. The symbol × denotes timing and number of breath alcohol concentrations (BrAC) and ear temperature measurements.

Figure 2

BrAC curves over time in two groups of women tested during (open symbols) and after lactation (solid symbols). Group PB breast pumped one hour before (N=5; circles) whereas Group PA breast pumped beginning 0.6 hours after (N=7; triangles) drinking a 0.4g dose of ethanol per kg of body weight. Panel A depict values obtained during Fed Condition and Panel B depict values obtained after an overnight Fasted Condition. Timing of breast pumping is indicated by hatched box and meal ingestion (for Fed Condition) by arrow. For both food conditions, reproductive stage significantly interacted with group and time (Fed condition: F(14,140)=2.86; p<0.001; Fasted condition: F(14,140)=5.93; p<0.0001). See text for further analyses.

Figure 3

Temperature Response to Fasting and an Alcohol Challenge. Panel A. Ear temperature (°C) before and after women (Groups PA and PB combined) drank a 0.4g/kg dose of alcohol (at time 0) during fed (solid) and fasted (open) conditions. Temperature readings taken during lactation are depicted as squares and those taken after lactation are depicted as triangles. There were a significant interaction between reproductive stage (during lactation, after lactation, condition (fed, fasted) and time since alcohol consumption (F(12,108)=1.84; p=0.05). See text for further analyses. Panel B. Delta temperature scores relative to respective baseline values during fed (solid) and fasted (open) conditions and during lactation. Delta temperatures from lactating women are depicted as squares and those of women post lactation are depicted as triangles.

Figure 3

Temperature Response to Fasting and an Alcohol Challenge. Panel A. Ear temperature (°C) before and after women (Groups PA and PB combined) drank a 0.4g/kg dose of alcohol (at time 0) during fed (solid) and fasted (open) conditions. Temperature readings taken during lactation are depicted as squares and those taken after lactation are depicted as triangles. There were a significant interaction between reproductive stage (during lactation, after lactation, condition (fed, fasted) and time since alcohol consumption (F(12,108)=1.84; p=0.05). See text for further analyses. Panel B. Delta temperature scores relative to respective baseline values during fed (solid) and fasted (open) conditions and during lactation. Delta temperatures from lactating women are depicted as squares and those of women post lactation are depicted as triangles.