Potentially deadly. But this depends on what kind of drugs you are taking with alcohol. There are usually no immediate symptoms that you are causing internal damage until it is too late. Typical signs of internal bleeding are usually visible in your faeces black tarry with suspended blood are the danger signs.

Opiate based drugs such as Morphine, Codine & Demerol combine badly with alcohol and certain popular brands of opiate based pain killers such as Vicodin also contain acetaminophen (contained in Tylenol and many other painkillers) Acetaminophen is one of the main causes of overdose and liver failure in the US.

Other groups of drugs such as anti depressants, Antipsychotics (like thorazine) and sedatives or Hypnotic drugs Like Valium and Ativan can also lead to death when combined with alcohol.

To be safe, never combine alcohol with prescription medication. At the very least it will reduce the effectiveness at worst it could kill you.

Death by liver failure and other effects caused by ingesting prescription medication and alcohol can be a very long painful and unpleasant process.

You need to talk to your doctor about the prescriptions you take and find out if there are one's that you need to avoid when you drink alcoholic beverages. Some combinations can be lethal. If it states on the bottle (usually on a sticker) to avoid alcohol you know it's not a good combination it's either lethal or it can make the side effects worse.

If your experiencing internal bleeding you need to seek medical attention. Black stool could be an indicator of internal bleeding also. There could be bleeding ulcer, Crohn's Disease, polips, cancer, or bad case of hemmroids from the medication drying out the intestinal lining in your colon. There are numerous reasons, bleeding is always serious though if you haven't had medical attention for it, you must seek it to eliminate further serious health issues. In February 1998 my brother was 39 years old, started having black stool, he started having severe pain in his back, he had never went to the doctor. He went to the emergency room the docters there were going to release him with painkillers, he demanded they find out what was causing the severe pain, the next day the doctors called in an Oncologist. He was diagnosted on February 25, 1998 with a form of Hodgkin's, he had cancer in his speen, liver, and intestines. It was the kind of cancer that is hereditary, forms for about 5 years prior to symptoms and by the time they discover it, it's to late. He lost his battle with it on April 25, 1998 and we placed him to rest on April 27, 1998.

If nothing else call 1411 or 800-555-1212 for the National Poison Control Center, they can go over that with you and advise you on the phone what you need to do or avoid.