Hi, Reese s pinworm medication contains pyrantel pamoate which is effective against pin worm infection. But repeated use may have caused resistance in the worms and they may have stopped responding to treatment. I suggest to get in touch with your GP for change of anti-helminthic prescription. Pyrvinium pamoate and Mebendazole are effective alternatives. Repeated infection can be prevented by: Treatment of other members in the family. Improved personal hygiene and cleanliness is very important. Cut your nails short. Washing your hands before eating is a must. Bed linens and night clothes need to be washed regularly. I hope this advice helps you to deal with the infection effectively. thanks.