Suppositories
are solid dosage forms intended for insertion into body orifices, i.e.,
rectum, where they melt, soften or dissolve and exert local or systemic effects
Suppositories have various
shapes and weights; the shape and size must be such that it can easily be inserted into the intended orifice without causing undue distension, and once inserted, it must be retained for the appropriate period of time
Rectal suppositories are inserted
with the fingers
Inserts
are solid dosage forms that are inserted into a naturally occurring
(nonsurgical) body cavity other than the mouth or rectum, i.e., vagina and urethra
Certain vaginal inserts (and tablets) may be inserted
high in the tract with the aid of an appliance
Rectal suppositories characteristics
Usually about 32 mm (1.5 in.) long
- are cylindrical
- and have one or both ends tapered
- Some shaped like a bullet, torpedo or the little finger
Depending on the density of the base and the medicaments in the suppository, their
weights may vary
Adult rectal suppositories weigh approximately 2 g when cocoa butter (theobroma oil) is
employed as the base
– Ones used for infants and children are about half the weight and size and assume a more
pencil-like shape ( 1g)
Vaginal inserts
Also called vaginal suppositories and pessaries
- can be tablets
Vaginal inserts characteristics
Usually globular, oviform or coned-shaped and weigh about 5 g when cocoa butter is the base
Urethral inserts
Also called urethral suppositories and bougies
Urethral inserts characteristics
Slender, pencil-shaped and intended for insertion into the male or female urethra
- For males, may be 3 to 6 mm in diameter and approximately 140 mm long, although
this may vary
• When cocoa butter is employed as the base, these weigh approximately 4 g
• For females, are about half the length and weight of the male verversions, being about 70 mm long and weighing about 2 g, when made of cocoa butter
Urethral inserts are used for
the treatment of local infections and erectile dysfunction
Local and systemic action of suppositories and insert
Once inserted, the suppository base melts, softens or dissolves, distributing its
medicaments to the tissues of the region
Rectal suppositories intended for local action are most frequently used to
relieve constipation or the pain, irritation, itching and inflammation associated with
hemorrhoids or other anorectal conditions
Vaginal inserts intended for local effects are employed mainly as
contraceptives, antiseptics in feminine hygiene, and as specific agents to combat an invading pathogen
Mucous membranes of the rectum and vagina permit
absorption of many soluble
drugs
– Rectal used frequently, the vagina not as frequently for systemic absorption
Why might it not be practical for oral administration of a drug
in some circumstances during nausea and vomiting or convulsions, in uncooperative patients and before surgery)
The rate and extent of rectal drug absorption are
often lower than with oral
absorption, possibly an inherent factor owing to the relatively small surface area available for drug uptake
Some advantages of rectal
administration
- Drugs avoid, at least partially, the first-pass effect
- Drugs destroyed or inactivated by the pH or enzymatic activity of the stomach or
intestines need not be exposed to these destructive environments - Larger doses can be administered, compared to oral administration
- Drugs irritating to the stomach may be given without causing such irritation
- No taste limitations
- Convenient for administration of drugs to patients who are unable or unwilling to
swallow medication, i.e., infants - An effective route in the treatment of patients with vomiting
- Achievement of a rapid drug effect systemically, as an alternate to injection
Some disadvantages of rectal administration
- Not preferred by patients
- Rectal absorption can be erratic
- Can be expelled after insertion
- The absorbing surface area of the rectum is much smaller than that of the small intestine
- The fluid content of the rectum is much less than that of the small intestine, which may affect dissolution
- Local irritation – Long term medication with rectal ergotamine and acetylsalicylic acid, for example, may result in rectal ulceration, and irritation after a single
administration of several drugs and formulations has been described
Factors that affect rectal absorption of drug
- Physiologic factors
2. Physicochemical factors of the drug and the base:
Physiologic factors
- Colonic content
- Circulation route
- Essentially neutral pH and lack of buffering capacity of the rectal fluid
Physicochemical factors of the drug and the base:
- Lipid-water solubility
- Particle size
- Nature of the base
Colonic content –
Greater absorption when rectum is empty
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Thermodynamics60
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Drug Absorption and Oral Route I and II109
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Powders57
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Tablets50
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Capsules40
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Drug stability58
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Drug stability II62
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Oral Delivery of Modified Release solid dosage forms84
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Semisolid dosage forms and rheology86
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Semisolid dosage forms and rheology part II48
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Suppositories and inserts57
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Solutions in Therapy85
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Introduction to surfactants51
