Retinol weakens the anti-inflammatory properties of glucocorticoids. It is forbidden to use it in combination with cholestyramine, as well as nitrites, as they violate the absorption of the substance. In addition, retinol is prohibited to be taken with retinoids, because such a combination is toxic.
Because of the risk of hypervitaminosis type A it is forbidden to combine with other drugs, which contain retinol.
Ascorbic acid potentiates the toxic properties and effectiveness of sulfanilamides (can develop crystalluria), as well as penicillin. In addition, it enhances the absorption of iron and aluminum (therefore it must be carefully combined with aluminum-containing antacids) and weakens the effectiveness of the anticoagulants with indirect action and heparin. The medicine in high doses weakens the medicinal properties of tricyclics with neuroleptics (phenothiazine derivatives), and in addition the processes of reabsorption of amphetamine substance inside the tubules. In addition, hexavit disrupts renal excretion of mexiletine.
Ascorbic acid is allowed to be consumed no earlier than 2 hours after the injection of deferoxamine.
Long-term use of the vitamin complex in high doses weakens the effectiveness of therapy with disulfiram.
Vitamin C increases the overall value of ethanol clearance. It also increases the secretion of oxalates along with urine and increases the likelihood of developing crystalluria in the case of salicylates.
Absorption of ascorbic acid decreases in the case of a combination with oral contraception, as well as with vegetable or fruit juices and alkaline drink.
Thiamin can affect the polarization inside the synapses of the muscles and nerve endings, so that it can reduce the curare like effect from the muscle relaxants.
Riboflavin has an incompatibility with streptomycin, and also reduces the impact of antibacterial drugs (such as doxycycline with oxytetracycline and lincomycin, as well as tetracycline and erythromycin). Amitriptyline with tricyclics and imipramine slows the metabolism of riboflavin (especially inside the heart tissue).
Pyridoxine reduces the effectiveness of levodopa, and in addition prevents or reduces the toxicity of isoniazid and other antituberculous drugs.
In the case of a combination of niacin with lovastatin, rhabdomyolysis can sometimes develop.