Suppositories

A suppository is a solid or semisolid dosage form intended for insertion into a body orifice (e.g., rectum, vagina, urethra). Suppositories are used to deliver drugs for their local or systemic effects.

Suppositories differ in shape and size. Rectal suppositories are usually cylindrical and tapered to a point, forming a bullet–like shape. As the rectum contracts, a suppository of this shape moves inward rather than outward. Suppositories for adults weigh approximately 2 g. Suppositories for children and infants are smaller. Vaginal suppositories are oval and typically weigh approximately 5g. Drugs administered by this route are intended for a local effect, but systemic absorption may occur. Antiseptics, contraceptive agents, and drugs used to treat trichomonal, monilial, or bacterial infections are often formulated as suppositories. Urethral suppositories are typically long and tapered. They are approximately 60 mm long and 4–5 mm in diameter They are administered for a local effect and are most commonly used as antiinfective agents.

Rectal suppositories are often used for systemic effects (e.g., relief of hemorrhoids) Rectal suppositories are useful when oral administration is inappropriate, as with infants, debilitated or comatose patients, and patients who are nauseous, vomiting, or have gastrointestinal disturbances. Some drugs can irritate the stomach, therefore, the use of suppositories is preferable.

Suppositories are prepared by hand–rolling, compression or molding. Hand–rolling involves molding the suppository with the fingers after a plastic suppository mass has been formed. Compression is generally used when cocoa butter is used as a base. The fusion method is the principal technique for commercial manufacture of the suppository.

Suppository bases should meet the following criteria. They should: 1) remain firm at room temperature to allow insertion. The suppository should not soften at temperatures below 30 °C to avoid melting during storage; 2) dissolve rapidly in the cavity fluid; 3) be inert and compatible with a variety of drugs; 4) be nonirritating and nonsensitizing; 5) have an acid value of less than 0.2, a saponifying value of 200–245, and an iodine value of less than 7 if the base is fatty. If an oil–soluble drug is incorporated into an oily base, then the rate of absorption is somewhat less than that achieved with a water–soluble base. Conversely, a water–soluble drug tends to pass more rapidly from the oil phase to the aqueous phase. Therefore, if rapid onset of action is desired, the water–soluble drug should be incorporated into the oily base.

Bases that melt include cocoa butter and combinations of fats and waxes. Cocoa butter (theobroma oil) is the most widely used suppository base. It is firm and solid up to the temperature of 52 °C, at which point it begins to soften. At 34–35 °C, it melts to produce a thin, bland, oily liquid. Cocoa butter is a good base for a rectal suppository, but it is less suitable for vaginal and urethral suppositories. Polyethylene glycol (PEG) derivatives are water–soluble bases suitable for vaginal and rectal suppositories.

Containers for the suppositories are determined by the preparation method and the base used. Hand–rolled and molded suppositories should be dispensed in special boxes that prevent the suppositories from coming into contact with each other. If appropriate, a «refrigerate» label should appear on the container. Regardless of the base or medication used in the formulation, the patient should be instructed to store the suppositories in a cool dry place.

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