At least one solid drug form (2) is fed into a capsule (4), housed inside a pocket (8) on a first conveyor (5) movable along an endless first path (P1) extending in a given first plane (S1), by means of a seat (27) on a second conveyor (22) movable along an endless second path (P2) extending in a second plane (S2) parallel to the first plane (S1) the seat (27) receiving the solid form (2) from a vibratory distributor plate (10), and releasing the solid form (2) to the pocket (8).