Rectal suppositories are used to administer a predetermined drug dosage to treat a variety of diseases and symptoms in a variety of patient populations. Certain medical conditions, such as digestive disorders, may be more effectively treated when the suppository is placed in a particular location of the patient's anal canal or rectum. An apparatus for inserting a suppository can include an applicator having a barrel, such as a hollow cylindrical body, and a plunger, such as a substantially cylindrical elongated body. The apparatus can include features to ensure that beneficial gas flow paths associated with the plunger or the barrel are maintained or that the apparatus can accommodate suppositories of different sizes. Embodiments may include features to facilitate gripping and manipulation of the apparatus for use by patients with limited dexterity. These benefits may encourage patients to maintain a course of treatment, thereby potentially avoiding additional complications, hospitalization, and costs.