Coadministration has not been studied. Nicotinamide is metabolized by nicotinamide methyltransferase to N-methylnicotinamide which is then metabolized by xanthine oxidase and aldehyde oxidase. Renal elimination of unchanged nicotinamide is minimal. A pharmacokinetic interaction is unlikely with nicotinamide itself. However, nicotinamide can be found in multivitamin preparations which may also contain polyvalent cations. As the effect of cationic complexation with raltegravir cannot be excluded, caution is recommended as raltegravir concentrations may be reduced.