March 23 - Suppositories Flashcards
What are suppositories? Why are they used for? Describe their shape
Suppositories are solid dose forms for insertion into the body orifices where they melt, soften or dissolve releasing drug for local or systemic effect. Most commonly used for rectal or vaginal insertion. Shape and size such that easy to insert and remain in place after insertion. Rectal usually bullet-shaped and for adults about 2 g. For children smaller and more cylindrical. Vaginal ovoid shape about 5 g.
How do suppositories exert their local and/or systemic action? How do rectal suppositories work? What do rectal suppositories typically contain?
After insertion mass melts, it softens or dissolves and medication is released to surrounding tissues. Rectal suppositories for local effect used to treat pain, inflammation and itchiness associated with hemorrhoids or other anal-rectal conditions. Contain components like local anesthetics, vasocontrictors, astringents, analgesics, emollients and protective agents. Some used to treat constipation and contain glycerin which has a mild local irritating effect and lubricates. Some may contain laxative agents
How do vaginal suppositories work?
Vaginal inserts usually used for local effect. Includes contraceptive effects, antiseptics for hygiene or local delivery of agent to treat infection due to yeast like Candida or protozoa like Trichomonas sp
How do systemic suppositories work? Why do we use systemic suppositories? What are the advantages of systemic suppositories? What is a disadvantage of systemic suppositories?
Systemic effect may be achieved using suppository and examples include drugs for treating nausea and vomiting, drugs to treat migraine headaches, some analgesics and some tranquilizers. Advantages for systemic use include: bypasses GI tract and first-pass metabolism, drugs irritating to stomach can be given this way, for patient unable to use oral route (vomiting, unconscious). Disavantage is absorption is erratic with inter-patient variability
What factors affect drug absorption?
Physiological
Physiochemical
Describe the physiological factors that affect absorption. Describe the rectum and how the rectum absorbs drug. What can affect drug absorption?
Adult rectum is about 20 cm long containing 2-3 ml of inert mucous fluid. Absorption is efficient due to the large surface area and extensive blood and lymphatic vascularization. Conditions like inflammation, diarrhea, tissue dehydration, presence of tumors or polyps will affect absorption. Drugs avoid first-pass metabolism and are picked up by both blood and lymphatic vessels
Describe the physiochemical factors that affect absorption
Contents of empty colon have neutral pH with little buffer capacity. Ionic form of the drug when it is administered will not be affected. Usual properties of solubility, partition coefficient and particle size will affect extent or rate of absorption. Properties of base will affect absorption (melt or dissolves, hydrophilic/hydrophobic will interact with the drug)
Describe suppository bases. What is important with bases? How do bases affect the drug release? How are bases classified?
Suppository base must remain solid at room temperature but soften, melt or dissolve at body temperature (37ºC). Drug release can be affected by base: cocoa butter melts readily at body temperature but immiscible with colonic fluid so fat-soluble drugs remain in base, lipid-soluble drugs better released from water soluble polyethylene glycol (PEG). Bases may be classified as oleaginous and water soluble or miscible
Describe oleaginous bases. Give an example of an oleaginous base. What’s the melting point? What happens when you melt these bases? What happens if you were to add phenol? What are other examples of oleaginous bases? What is the benefit with oleaginous bases?
Cocoa butter is widely is used and is in this group. They are triglycerides which melts at 30-36ºC. Forms polymorphs and if heated beyond melting point forms alpha polymorph which is liquid at room temperature. Material like phenol lower mp of cocoa butter so you can add up to 4% beeswax to compensate. Some semi-synthetic bases which do no form low temperature melting polymorphs available. Fattibase - triglycerides from palm and coconut oil. Witepsol - triglycerides for C12-C18 saturated fatty acids. These bases are good for rectal irritation
Describe water soluble and miscible bases. What does this group consist of? What is important about PEG? How is the medication released? What is important about storage? What is important for patient to know? When is glycerinated gelatin used? What is the make up of these suppositories? How is the medication released form these suppositories? What are glycerin bases made up of?
Group consists of polyethylene glycols (PEG) and glycerinated gelatin. PEG come in variety of molecular weights designated by values of 200-8000 with lower values being liquid. Higher value, higher melting point. Usually use a combination of PEG, fuse and incorporate medication. Release medication by slowly dissolving. Hydroscopic so need to protect from moisture but moisten just prior to use otherwise stinging sensation. Glycerinated gelatin is often used for vaginal inserts. Consist of about 20% gelatin, glycerin 70% and water 10%. Release slow and through softening and dissolution. Miscible with vaginal secretions. Glycerin base can be made with glycerin 85%, sodium stearate 9.5% and water 5.5%
Describe the preparation of suppositories. How are suppositories prepared? What is the most common method? What are the steps?
They are prepared by molding, compression or hand rolling and shaping. Molding is the most common. First, melt the base using the least possible amount of heat (water-bath). Incorporate medicinal substances by mixing with some molten base using spatulation. Pour into mold cavities (careful with suspended materials). Stir while pouring just above congealing temperature to prevent material from settling in the tip. Pour a small excess to allow for contraction. After the mass has set, remove (if appropriate) and package.
What preparing suppositories, what should be taken into account?
Metal molds should be lubricated prior to use
Excess material should be scraped away prior to opening
Care should be taken not to scratch the surfaces of the mold
Always prepare an excess to allow for losses
Describe the molds used to prepare suppositories
Made of metal and come in a variety of sizes and shapes
Plastic molds are available as well and plastic shells become part of the packaging system
How should suppositories be stored?
Suppositories containing glycerin should be in glass or otherwise protected from moisture and may need to be refrigerated
PEG bases may also need protection from moisture
Cocoa butter based products should be individually wrapped to prevent adhesion
What is important with regards to patient counseling about suppositories?
Inform regarding storage
Ensure they any wrapping is removed prior to use
Explain the function of shape and which end is to be inserted
If half a suppository is prescribed, cut lengthwise
Dip PEG or glycerin based products in water prior to use to avoid burning sensation
