Since bacteriostatic drugs may interfere with the bactericidal action of penicillins, it is advisable to avoid giving tetracycline-class drugs in conjunction with penicillin.
Source: FDA drug label - demeclocycline hydrochloride
Demeclocycline Hydrochloride Interactions
Brand names: Demeclocycline Hydrochloride
2 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 penicillins, it is advisable to avoid giving tetracycline-class drugs in conjunction with penicillin. Concurrent use of tetracyclines with oral contraceptives may render oral contraceptives less effective.
Source: FDA drug label - demeclocycline hydrochloride