You can take anything >you< want, but it is irresponsible to recomend anything unless you know the possible side/harmful effects it could have. More specifically when taking harsh chemicals like aspirin etc on an empty stomach like on the MC.
This site and the internet have an incerdible amount of readily accesible info. You should do a little research before recomending anything that you either don't know anything about the possible effects or even if you're not sure. Some of the folks looking into the Master-Cleanse might be quite ill and your "uninformed" recomendation could cause them great harm.
Some info on aspirin:
"Aspirin, like other salicylates, has the property that in concentrated solution can attack and dissolve tissues. An aspirin in the stomach may attach to the stomach wall and cause a bleeding ulcer."  A recent report from the Boston University school of Medicine confirms that aspirin can irritate the stomach lining, sometimes causing severe upper gastrointestinal bleeding and, in rare instances, death. [3,4].
Certain drugs, such as aspirin, cortisone, and other anti-inflammatory agents, and cinchophen, are known to provoke ulcers and gastric hemorrhage. This is especially the case when a deficiency of ascorbic acid [vitamin C] is present.
"It is drugs, especially the analgesics and antipyretics such as aspirin, that are responsible for most of the five thousand deaths by poisoning that occur each year in the United States. Of that mournful total about twenty-five hundred are children. About four hundred of these children die each year of poisoning by aspirin (acetylsalicylic acid) and some other salicylate
"Some people show a severe sensitivity to aspirin, such that a decrease in circulation of the blood and difficulty in breathing follow the ingestion of 0.3 g to 1 g (one to three tablets.)
More common side effects may include:
Abdominal cramps or pain, abdominal discomfort, bloating and gas, constipation, diarrhea, dizziness, fluid retention and swelling, headache, heartburn, indigestion, itching, loss of appetite, nausea, nervousness, rash, ringing in ears, stomach pain, vomiting
Less common or rare side effects may include:
Abdominal bleeding, anemia, black stool, blood in urine, blurred vision, changes in heatbeat, chills, confusion, congestive heart failure, eepression, dry eyes and mouth, emotional volatitity, fever, hair loss, hearing loss, hepatitis, high or low blood pressure, hives, inability to sleep, inflammation of nose, inflammation of the pancreas or stomach, kidney or liver failure, servere allergic reactions, shortness of breath, skin eruptions or peeling, sleepiness, stomach or upper intestinal ulcer, ulcer of gums, vision loss, vomiting blood, wheezing, yellow eyes and skin.
Special warnings about this medication:
Peptic ulcers and bleeding can occur without warning.
This drug should be used with caution if you have kidney or liver disease, or are severely dehydrated; it can cause liver or kidney inflammation or other problems in some people.
Motrin may cause vision problems. If you experience any changes in your vision, inform your doctor.
Mortin may prolong bleeding time. If you are taking blood-thinning medication, this drug should be taken with caution.
This drug can cause water retention. It should be used with caution if you have high blood pressure or poor heart function.
Motrin may mask the usual signs of infection or other diseases. Use with care in the presence of an existing infection.
If you have diabetes, remember that the suspension contains 1.5 grams of sucrose and 8 calories per teaspoonful.