Serious muscle problems are more common when Vytorin is first started or when the Vytorin dosage is increased, but it can happen at any time. There are also certain medicines that, when taken simultaneously with Vytorin, can increase the risk for serious muscle problems. These medicines include:
Some of these medications should not be combined with Vytorin at all, while others can be taken as long as the Vytorin dosage is reduced (see Vytorin Drug Interactions for more information).
Keep in mind that the risks increase with higher Vytorin dosages and appear to be highest in the first year of use. The highest Vytorin dosage (10/80 mg a day) should be reserved only for people who have already been on that dosage for a year or more without any muscle problems. For everyone else, the maximum dosage is 10/40 mg a day (or even less, in some situations).
Grapefruit juice and grapefruit products, including grapefruit supplements, should also be avoided (see Grapefruit Juice and Vytorin).