After considerable research by the present author, a standard design for 5-gram zinc acetate lozenges can be recommended, although advanced 3.5- to 5-gram designs based upon the standard design are also presented and are preferred.

Standard 23-mg zinc lozenges having a ZIA value of 148+12.5 when used 9 times per day, are compounded with 77.2 mg zinc acetate dihydrate USP (Heico Chemicals, Delaware Gap, Pennsylvania) in a 7/8-inch diameter, 5-gram directly compressible dextrose (Emdex(r) - Edward Mendell Co., Carmel, New York) base. The preferred flavoring is peppermint oil (0.5 to 5 mg). The most economic application of peppermint oil is by direct spraying and thorough mixing of peppermint oil with Emdex(r), as flavor oil requirements are reduced by two-thirds compared with platting peppermint oil onto silica gel. Sodium saccharin (1 to 10 mg), menthol (1 to 10 mg), and magnesium stearate lubricant (0.5 to 1.25 percent) are used as needed. The first stability constant for zinc and dextrose is log K₁ = 0.01, showing essentially complete lack of stability.(13) Binders, lake colors, and ionic additives (other than chemically insignificant amounts of sodium saccharin) are not added to preclude inadvertent zinc chelation.

When sufficiently hard throughout (about 6 to 10 tons applied pressure with precompression), these lozenges produce 47.5 grams saliva and dissolve in about 41.6 minutes. Resultant salivary pH is 5.5 to 6, and salivary Zn²⁺ ion concentration is 8.3 mMolT. Zn²⁺ ion concentration is slightly greater than the concentration used in the successful trial in 1984 by Eby and co-workers.

Zinc acetate lozenges taste pleasant but are astringent, with astringency increasing with increased zinc acetate content. Strong flavoring and sweetness stimulate saliva flow and reduce lozenge ZIA values, while increases in zinc increase astringency and reduce saliva production. In standard design lozenges, least cost, best taste, and maximum ZIA values occur in lozenges having minimal sweetness and flavor.

The standard lozenge design suggested relies upon Emdex(r) as a tablet-base in preference to other bases because data as to the very low stability constant exists for zinc and dextrose, absolutely eliminating chelation by the tablet base as a source of lozenge failure.

Comparison of Zinc Gluconate and Zinc Acetate in Identical Tablet Bases

Because zinc acetate releases 3.33 times more Zn²⁺ ion than zinc gluconate at physiologic pH 7.4, much more latitude is available using zinc acetate in the design of high ZIA lozenges. Standard design zinc acetate lozenges with an Emdex(r) base producing an average ZIA value of 148+12.5 can be expected to perform well against common colds in essentially all patients. A favorable response with zinc acetate lozenges could even be expected in patients like Tester #2 who produced very large amounts of saliva. Had zinc gluconate -- rather than zinc acetate -- been used in the standard design Emdex(r) base and tested by Tester #2, the value would have been ZIA 33 rather than 109. Limited efficacy against colds in Tester #2 may be theorized to have then resulted.

Medicinal Additives

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Table 12. Medicinal ingredients for incorporation into common cold lozenges

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		 	anesthetics, such as lidocaine
		 	other antiviral agents
		 	antimycoplasmal agents
		 	anti-inflammatory agents
		 	interferon
	 		antibiotics
	 		nasal decongestants 
	 		antihistamines
		 	antinausea agents
		 	analgesics
		 	cough relievers
	 		waxes 
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