As a breastfeeding mom, you should be able to enjoy the occasional alcoholic beverage from time to time without fear of harming your baby, provided you drink responsibly. Your concern over how to resume breastfeeding after enjoying a cocktail is a common one, and it is a good question to ask.
Not Necessary to Pump and Dump Breastmilk
While you might think that you must "pump and dump" your breastmilk after you have finished drinking alcohol, it is completely not necessary to do for your baby's sake. The only reason you would need to pump your milk would be to relieve any discomfort you are experiencing from engorgement. If you need to express milk to relieve pain, the breastmilk pumped during this time should be thrown out.
If you aren't bothered by the lapse of feedings, then the simplest thing to do is give yourself time and allow your blood-alcohol levels to return to normal.
The explanation of when it is safe to breastfeed after drinking alcohol is a bit complicated. However, the really short answer is when your body has rid itself of alcohol, breastfeeding can safely continue. The complex part is that the amount of time it takes for alcohol to leave your system will vary based on several factors such as your body weight, how much alcohol you drank over a period of time, and the amount of alcohol in your beverage of choice.
The bottom line: it isn't necessary for you to pump and dump your milk after a night of drinking. Time is all you need and the alcohol will naturally leave your breastmilk just as it does your blood.
For more information on how alcohol affects milk supply, safety issues with breastfeeding and alcohol, and other facts read Alcohol and Breastfeeding:What You Need to Know about Breastfeeding and Drinking Alcohol