Topical Dosage Forms: Gels, Creams, Liniments, and Local Delivery

Flashcards covering gels, creams, liniments, and targeted local delivery from the lecture notes.

What is a gel?

A solid or semisolid system of dispersion of small or large molecules in an aqueous liquid vehicle rendered jellylike by a gelling agent.

Name gelling agents used in gels.

Synthetic: carboxymethyl cellulose (CMC) or hydroxyethyl cellulose (HEC); natural gums: tragacanth; carbomers: high molecular-weight, water soluble.

What are the two gel classifications?

Single phase and two phase.

What is a cream?

A semisolid preparation with lower viscosity that is either O/W or W/O, forming two phases.

What causes light scattering in creams?

Light scattering is due to reflection of light from the internal dispersed phase.

Cold creams are which type of emulsion?

W/O (water-in-oil) emulsion.

What are the current and most common O/W creams described?

Fatty acid micro-dispersion or vanishing creams.

Why are creams considered a good delivery system?

They provide good delivery and have good patient acceptance (compliance).

What happens when water evaporates from a cream applied to the skin?

The drug is concentrated on the skin surface.

What must be avoided regarding drug stability in creams?

Drug crystallization must be avoided.

What is a liniment?

A semi-solid preparation with high oil content intended for rubbing or massaging into the skin to provide relief.

Name some oils used in liniments.

Mineral oil, castor oil, olive oil; emollients such as lanolin or beeswax.

What kinds of active ingredients are found in liniments?

Analgesics, counterirritants (menthol, camphor), rubefacients (capsaicin), anti-inflammatory agents (salicylates), muscle relaxants, antifungal agents.

Capsaicin in liniments

Counter irritant or rubefacient for external use only.

What is a rubefacient?

A substance that produces redness by dilation of capillaries and increased blood circulation, often acting as a counterirritant.

Name common rubefacients.

Capsaicin (from Cayenne), salicylates (oil of wintergreen, methyl salicylate), nicotinate esters.

Through what mechanism do rubefacients often act?

They act via transient receptor potential (TRP) ion channels.

What is ThermaCare?

A heat therapy product that uses capsaicin (0.1%) for pain relief.

What is targeted (local) delivery in topical products?

Delivery to epidermal and dermal layers without systemic delivery for local effects.

Give examples of targeted local delivery products.

Antiseptics (Purell, Aloe Vera); Antipyretics (Calamine Lotion); Hydrocortisone and camphor; Keratolytics (Compound W, Salicylic acid, sulfur); Antibiotics (Neosporin, Polysporin); Antifungals (Polyenes, Imidazoles, Allylamine); Astringents (Preparation H, Xylocaine, Zinc Oxide).