Semi-Solid Dosage Forms

• Semisolid dosage forms are topical medications for therapeutic, protective, or cosmetic use.
• They can be applied to the skin, nasally, vaginally, or rectally.

Site of applications of SSD

• Semi-solid dosage (SSD) forms are a type of medication that is neither solid nor liquid.
• These medications can be applied to the skin, nasal mucosa, cornea, and rectal or vaginal tissue (often via suppository).
• They may also be applied to buccal tissue, ear, or urethral membrane.

Rationales behind SSD

• SSDs have fewer side effects and avoids first-pass metabolism.
• SSDs act locally and are convenient for unconscious patients or patients having difficulty with oral administration.
• SSDs are a suitable dosage form for bitter-tasting drugs and are more stable than liquid dosage forms.

Disadvantages of semi-solid dosage form

• SSDs do not have dosage accuracy, and the base used in the semi-solid dosage form can be easily oxidized.
• SSDs may cause staining and are bulky to handle.
• Application with a finger may cause contamination, and SSDs are less stable than solid dosage forms.
• SSDs may cause irritation or allergy in some patients.

PHYSICAL PROPERTIES OF SEMISOLIDS

• Smooth texture
• Non-gritty
• Elegant in appearance
• Non-dehydrating
• Non greasy and non staining
• Non-hygroscopic

PHYSIOLOGICAL PROPERTIES OF SEMISOLIDS

• Should not alter membrane functioning
• Non-irritating

APPLICATION PROPERTIES OF SEMISOLIDS

• High aqueous wash ability
• Easily applicable with efficient drug release

INGREDIENTS USED IN PREPARATION

• Bases, preservative, humectants, antioxidants, emulsifier, gelling agent, permeation enhancer, and buffers

BASES

• Bases are the most important ingredient used in the formulation of semisolid dosage forms.
• Ointment bases do not merely act as carriers of medicaments, but they also control the extent of absorption of medicaments.

CLASSIFICATION OF BASES

• Ointment bases are classified by the USP into four general groups.
• A- hydrocarbon bases (oleaginous bases) (Petrolatum, Paraffin, Lanolin.....)
• B- absorption bases (cold cream, anhydrus lanolin ...)
• C- water-removable bases (oil in water)
• D- water-soluble bases (polyethylene glycol)

ANTIOXIDANTS

• Oxygen is a highly reactive atom capable of becoming part of potentially damaging molecules commonly called "free radicals.”

PERMEATION ENHANCERS :

• Skin can act as a barrier.
• With the introduction of various penetration enhancers, penetration of the drug through the skin can be improved.

EMULSIFIER

• An emulsifier (emulgent) is a substance that stabilizes an emulsion by increasing its kinetic stability.

Antimicrobial preservatives

• Antimicrobial preservatives inhibit the growth of contaminating microorganisms, so addition of chemical antimicrobial preservatives to the formulation is required.
• Example: para-hydroxybenzoates (parabens)

Ointments

• Ointments are homogenous, translucent, viscous semi-solid preparations, most commonly a greasy, thick oil (oil 80% - water 20%) intended for external application to the skin or mucous membrane.
• Ointments may be medicated or non-medicated
• They are used as: emollient, lubricant, protective, therapeutic and prophylactic purpose

When to use ointments????

• Ointments are thicker than creams and lotions, making them ideal for treating conditions like eczema.
• Ointments provide a layer of protection for the skin.

Evaluation of ointments

• Includes assessment of penetration, rate of release of medicaments, absorption of medicaments into the bloodstream, and irritant effect

Penetration evaluation of ointments

• Weighed quantities of the ointments are rubbed over definite areas of the skin for a given length of time.
• Thereafter the unabsorbed ointment is collected from the skin and weighed.
• The difference between the two weights roughly represents the amount absorbed.

Rate of release of medicament

• To assess rate of release of medicament, a small amount of the ointment can be placed on the surface of nutrient agar contained in a Petri dish.

Rate of absorption of medicament

• A definite amount of ointments should be rubbed through the skin.
• Under standard conditions and medicaments are estimated in the blood plasma or urine

CREAMS

• Pharmaceutical creams are semisolid preparations containing one or more medicinal agents dissolved in either an o/w or w/o emulsion.
• Their consistency depends on the type of emulsion, and on the nature of the solids in the internal phase.

GELS

• Gels are homogeneous, clear, semisolid systems consisting of dispersions of small or large molecules in an aqueous liquid vehicle rendered jellylike by the addition of a gelling agent.

LOTIONS

• Lotion is a low-viscosity topical preparation intended for application to the skin.
• Lotion may be used as a medicine delivery system; many lotions, especially hand lotions and body lotions and lotion for allergies, are meant instead to simply smooth, moisturize, soften, and sometimes perfume the skin.
• Some skincare products, such as sunscreen and moisturizer, may be available in multiple formats, such as lotions.