Phenytoin and valproate increase the content of phenobarbital in the blood serum.
The effect of phenobarbital decreases with simultaneous administration with reserpine, increases when combined with amitriptyline, nialamide, diazepam, chlordiaazepoxide.
Reduces the effectiveness of oral contraceptives and salicylates.
Reduces the blood levels of indirect anticoagulants, glucocorticosteroids, griseofulvin, doxycycline, estrogens and other drugs that metabolize in the liver along the oxidation pathway (speeds up their metabolism).
Strengthens the effect of alcohol, neuroleptics, narcotic analgesics, miorslaksantov sedatives and hypnotics.
Acetazolamide alkalizing urine, reduces the reabsorption of phenobarbital in the kidneys and weakens its effect.
Reduces antibacterial activity of antibiotics and sulfonamides, antifungal action of griseofulvin.