Known interactions between the following drugs: Cephadyn, Doxycycline

Butalbital increases the rate at which doxycycline is broken down and removed from the body. If this happens, then less doxycycline is available for your body to use. This may decrease the antibacterial effectiveness of doxycycline. If butalbital and doxycylcine are taken together, the dose of doxycycline may need to be increased. You may want to ask your healthcare provider about this potential interaction if you think you are having problems.

Acetaminophen is broken down and removed from the body by the liver. If this happens too quickly, then potentially less of the drug would be available for the body to use and blood levels could become too low. This could either make acetaminophen less effective or delay its pain relieving and fever reducing effects. It could also increase the formation of byproducts from acetaminophen. Excessive levels of these byproducts can be harmful to the liver. Butalbital may cause acetaminophen to be broken down at a faster rate than normal. Based on information from several studies, the risk of experiencing liver damage is the greatest when a high dose of butalbital has been used, or when butalbital has been taken for a long period of time and an overdose of acetaminophen is consumed. However, this potential interaction does not appear to cause any harmful effects when the recommended doses of butalbital and acetaminophen are used. You may want to ask your healthcare provider about this potential interaction if you think you are having problems.