د.قاسم

Pharmaceutical preparations for external use

When any drug is manufactured so that it is used externally, it will contain the label For external use only this means that the drug should neither be swallowed nor injected.
There are two main types of externally used preparations:
Preparations which are applied to the skin.(topical preparations).
Preparations which are applied to the mucus membranes.
In either case the desired action of the drug could be either:
Local action.
Systemic action.
Preparations applied to the skin:
The stratum conium (the superficial skin layer) is the principle barrier to penetration of drugs to the skin, but at the same time it acts as a reservoir for drugs; a corticosteroid may be detectable even 4 weeks after a single application.
Drugs are presented in vehicles, e.g. cream, ointment, lotion, and these vehicles vary in the extent to which they increase the hydration of the stratum conium.
Absorption of the active ingredient (drug) through the skin varies with the site e.g. it is relatively low from the palm of the hand and soul of the foot, but increases progressively on the forearm, the scalp, the face, until on the scrotum and vulva the absorption is very high.
When the skin is damaged by inflammation, burn, or exfoliation absorption is further increased.
Preparations applied to the skin include the following:
Lotion, cream, ointment, liniment, gel, solution, spray, dusting powder, shampoo, and dermal patch

Lotion:

Is a liquid preparation which contains a cooling substance like menthol, which is used to cleans, cool, & relieve pruritus in acutely inflamed lesions. It is applied frequently to the skin. e.g. Calamine lotion.
Cream:
It is a semisolid preparation in which the drug is mixed with a fatty base in the form of emulsion which is miscible with water; creams are applied on wet surfaces because they mix well with secretions.
Ointment:
Is a semisolid preparation consists of a fatty (greasy) substance mixed with the active drug; the base could be soft paraffin, wax, or vasaline.
Ointments are generally immiscible with water and are used to treat dry surfaces such as psoriasis and chronic eczema.
Liniment:
It is a semisolid or liquid preparation which is thinner than ointment; it is applied to the skin by friction and it contains irritant substances such as camphor, salicylates, menthol, and capsaicin.
Liniments lead to vasodilatation at the area and are used to relieve pain due to musculoskeletal conditions.
Transdermal delivery of drugs: (Trasdermal Patch)
Drug is released by a rate-controlling membrane which provides a relatively stable plasma concentration of the drug; It overcomes 1st pass elimination in the liver.
e.g. postmenopausal hormone replacement therapy.
Preparations applied to the mucus membranes:
1-Preparations applied to the Eye, Ear, and Nose.
2-Local mouth preparations
3-Rectal preparations
4-Vaginal preparations
Preparations applied to the Eye, Ear, and Nose:
Eye drop: is an isotonic sterile solution which is instilled into the eye by a dropper.
Eye ointment: same as skin ointment but usually contains less concentration of the active ingredient and should not be irritant to the eye, it could be applied to the ear or nose.
Ear drop: is a watery or oily solution which is instilled into the ear, it might contain an antibiotic, antifungal, local steroid, or substance that dissolves wax in the external ear.
Nasal drop: is an isotonic solution which is instilled to the nose by a dropper, it usually contains a decongestant drug.
Nasal spray: it can be used either for local action like corticosteroid drugs, or for systemic action like some hormones e.g. hr- PTH, or Desmopressin.
Local Mouth preparations:
Mouth wash: (gargle) is used for local antiseptic action (e.g. chlorhexidine) which is used to treat local mouth infection, mouth wash is not suitable for children under six years of age.
Gels or jellies: are semisolid colloidal solutions or suspensions that can be used as a vehicle to drugs, e.g. antifungal agents.
Rectal preparations:
Rectal suppository: Conical shaped preparation containing a fatty base which melts at body temperature. Used either for:
Local action: e.g. in the treatment of hemorrhoids, or as laxative.
Systemic action: e.g. paracetamol suppository.
Rectal cream: can also be used for local action e.g. in treatment of hemorrhoids.
Enema: is a liquid that is forced into the rectum, either to
1- Induce bowel movement (laxative effect).
2- Prednisolone enema is used in treatment of ulcerative colitis (local and systemic effect).
3-Barium enema is used as a diagnostic procedure.
Advantages of suppository:
Avoids stomach irritation .e.g. indomethacin suppository.
To get sustained action during night. e.g. aminophylline.
Used in uncooperative patient e.g. children.
To get local action, e.g. in treatment of hemorrhoids.
Patient who cannot take oral therapy
Vaginal preparations:
These are used for local vaginal action in the form of:
1-Vaginal tablet (ovule, pessary) e.g. metronidazole
2-vaginal cream e.g. triple sulfa cream
3-vaginal douche
Certain applicator is used to insert the medication.


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عملي (8) 24/11/2016