Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracyclines in conjunction with penicillin.
Source: FDA drug label - doxycycline hyclate
Doxycycline Hyclate Interactions
Brand names: Doxycycline Hyclate
5 interactions on record
Drug Interactions Because tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage. Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracyclines in conjunction with penicillin. Absorption of tetracyclines is impaired by antacids containing aluminum, calcium, or magnesium, and iron-containing preparations.
Source: FDA drug label - doxycycline hyclate
Barbiturates, carbamazepine, and phenytoin decrease the half-life of doxycycline.
Source: FDA drug label - doxycycline hyclate
However, there has been evidence of oncogenic activity in rats in studies with the related antibacterial drugs, oxytetracycline (adrenal and pituitary tumors), and minocycline (thyroid tumors).
Source: FDA drug label - doxycycline hyclate
However, there has been evidence of oncogenic activity in rats in studies with the related antibacterial drugs, oxytetracycline (adrenal and pituitary tumors), and minocycline (thyroid tumors). Likewise, although mutagenicity studies of doxycycline have not been conducted, positive results in in vitro mammalian cell assays have been reported for related antibacterial drugs (tetracycline, oxytetracycline).
Source: FDA drug label - doxycycline hyclate