Semisolid dosage forms

The chemical stability of active ingredients incorporated into ointments or creams is frequently dependent on the namre of the ointment 

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B. Semisolid Dosage Forms Ophthalmic Ointments and Gels... 

The present chapter deals with calculations involving topical semisolid dosage forms, which include ointments, creams, and pastes. 

Amongst the various types of semisolid preparations, ointments represent the type of extemporaneous preparations most likely to be prepared by a pharmacist. A variety of ingredients may be included in the formula of semisolid dosage forms. 

The practicing pharmacists may be called upon to prepare a semisolid dosage form in large quantity. The formulae for such preparations, in general, indicate proportional parts (or relative quantities) of ingredients to be used in compounding the desired total quantity. 

S. Proniuk, S. E. Dixon, and J. Blanchard. Investigation of the utility of an in vitro release test for optimizing semisolid dosage forms. Pharm. Dev. Technol. 6 469-476 (2001). 

SUPAC-SS Nonsterile semisolid dosage forms. Scale-up and postapproval changes chemistry, manufacturing, and controls in vitro release testing and in vivo bioequivalence documentation (May 1997). 

SUPAC-SS Nonsterile semisolid dosage forms manufacturing equipment addendum (December 1998, draft). 

Semisolid Dosage Forms The nature of the base (vehicle) used for the fabrication of semisolid dosage forms affects their hydrolytic stability. Increased degradation of benzylpenicillin sodium in hydrogels of various natural and semisynthetic polymers has been reported [14]. Also at pH 6 in Carbopol hydrogels, the percentage of undecomposed pilocarpine at equilibrium is a function of the apparent viscosity of the medium [15]. 

Semisolids dosage forms, as a class, are plastic in behavior, i.e., they retain their shape until acted upon by an outside force, in which case they deform and the deformations are permanent. The common denominator to all semisolid systems which gives them their special rheological character is that they all have a permanent three-dimensional structure. This structure is sufficient when undisturbed to impart solid-like properties but which is easily broken down and realigned under some strain or applied force (4). The semisolid systems used pharmaceutically include... 

Pastes may be defined as a semisolid dosage form that contains a large proportion (i.e., 20-50%) of solids finely dispersed in a fatty vehicle (basically an ointment base) for external application to the skin. The presence of a high concentration of solids makes them much stiffer than ointments. Like ointments, pastes form an unbroken... 

Tan E, Shah H, Leister K, et al. Transforming growth factor-a (TGF-a) in a semisolid dosage form preservative and vehicle selection. Pharma Res 1993 10(8) 1238 1242. 

The design of in vivo bioequivalence studies for semisolid dosage forms varies depending on the pharmacological activity of the drug and dosage form. A brief general discussion of such tests follows. 

For semisolid dosage forms the strength is usually stated as a weight/weight (w/w)... 

Guidance for Industry — SUPAC-SS Nonsterile Semisolid Dosage Forms... 

Preservatives such as sodium benzoate, sorbic acid, and methyl and propyl parabens have been used in liquid and semisolid dosage forms. There have been reports that the parabens have been inactivated when used in the presence of various surfactants. This loss of activity was thought to be due to the formation of complexes between the preservative and the surfactant. The interaction between polysorbate (Tween) 80 and the parabens has been demonstrated by a dialysis technique (Ravin and Radebaugh, 1990). It has also been shown that molecular complexes form when the parabens are mixed with polyethylene glycol (PEG) and methylcellulose. The degree of binding was less than that observed with Tween 80. Sorbic acid also interacts with Tweens but does not interact with PEGs. The quaternary ammonium compounds are also bound by Tween 80, which reduces their preservative activity. 

Changes in nonsterile semisolid dosage forms should be reviewed against the November 1999 FDA guidance for industry Changes to an Approved NDA or ANDA and the SUPAC Guidance for Industry Nonsterile Semisolid Dosage... 

CDER, FDA. Guidance for Industry, Nonsterile Semisolid Dosage Forms. U.S. Department of Health and Human Services (May 1997). 

The higher viscosity of semisolid dosage forms and transdermal systems may cause the rate of migration of leachable substances into these dosage forms to be slower than for aqueous solutions. Due to extended contact, the amount of leach-ables in these drug products may depend more on a leachable material s affinity for the liquid/semisolid phase than on the rate of migration. 

Semisolid dosage forms are traditionally used for treating topical ailments. The vast majority of them are meant for skin applications. They are also used for treating ophthalmic, nasal, buccal, rectal, and vaginal ailments. Various categories of drugs... 

The formulation, evaluation, and regulatory feature of the three most commonly used semisolid dosage forms, ointments, creams, and gels, are described in this chapter. 

Guidance for industry, Nonsterile semisolid dosage forms Scale-up and postapproval changes, U.S. Food and Drug Administration, May 1997, pp. 1-37. 

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