Unfortunately not. Unlike mineral supplements (like calcium) which compete for absorption with other minerals
and should ideally be taken apart from large doses of one another, the interactions of St. John's wort are due to its effects on how drugs are metabolized after they have been absorbed, so it can still affect drugs taken hours later. In addition, St. John's wort is typically given three times each day, so there is not much time when it will not be active and potentially interfere with other drugs.
More about the drugs with which St. John's wort can interact is found in the Concerns and Cautions section of the St. John's Wort Supplements Review
and the Drug Interactions section of the Encyclopedia article about St. John's wort