Coadministration has not been studied. Ispaghula husk passes predominantly unchanged through the gastrointestinal tract and there is little opportunity for marked absorption into or metabolism by the body. The mode of action of ispaghula husk is physical and does not depend on absorption into the systemic circulation. However, ispaghula husk may delay or reduce gastrointestinal absorption of other drugs and it is advisable to separate administration of ispaghula husk and orally administered drugs by 1 hour. [Note: this interaction is not specific for elvitegravir/cobicistat, emtricitabine and tenofovir alafenamide, but for any oral medication taken with ispaghula husk.]