Hydroxychloroquine and possibly chloroquine may increase theblood levels of metoprolol,but this is probably not clinically important.
Clinical evidence,mechanism, importance and management
Hydroxychloroquine 400mg daily for 8 days increased AUC and peak plasma levels of a single 100mg dose of metoprolol by 65 % and 72%, respectively, in 7 healthy subjects who were of extensive CYP2D6 metaboliser phenotype,(See reference number 1)see Genetic factors, . Hydroxychloroquine may inhibit metabolism of metoprolol by cytochrome P450 isoenzyme CYP2D6. The clinical significance of this interaction is unknown, but changes of this size in AUC of beta blockers have proved not to be clinically important. Other beta blockers that are extensively metabolised (see table 1 below,.) may behave like metoprolol, but those that are excreted unchanged in urine would not be expected to interact. In vitro study suggests that chloroquine may interact with metoprolol in same way as hydroxychloroquine (See reference number 2). More study is needed.
Somer M,Kallio J, Pesonen U, Pyykkö K, Huupponen R, Scheinin M. Influence of hydroxychloroquine on the bioavailability of oral metoprolol. Br J Clin Pharmacol (2000) 49, 549–54.
Lancaster DL,Adio RA, Tai KK, Simooya OO, Broadhead GD, Tucker GT, Lennard MS. Inhibition of metoprolol metabolism by chloroquine and other antimalarial drugs. J Pharm Pharmacol (1990) 42, 267–71.