Vibramycin Drug Interactions

There have been reports of prolonged prothrombin time in patients taking warfarin and doxycycline. Because the 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 doxycycline in conjunction with penicillin.
Absorption of tetracyclines is impaired by antacids containing aluminum, calcium, magnesium or other drugs containing these cations, iron-containing preparations and bismuth salts.
Alcohol, barbiturates, carbamazepine and phenytoin decrease the half-life of doxycycline.
The concurrent use of tetracyclines and methoxyflurane has been reported to result in fatal renal toxicity.
Concurrent use of tetracyclines may render oral contraceptives less effective.
Laboratory Test Interactions: False elevations of urinary catecholamine levels may occur due to interference with the fluorescence test.