A lot of metals are essential trace elements for vital body function: they are part of enzymes and have wide therapeutic activity. Drugs containing bismuth, zinc, silver, iron are used as antiseptic, drying, astringent, cauterizing, anti-inflammatory and antianemic agents.
Pharmaceutical products containing bismuth have signified astringent and anti-inflammatory effects. Getting into the acidic stomach medium bismuth preparations form chelate complexes as a of protective film on the damaged mucous membrane surface and as result protect gastrointestinal tract from effects of aggressive acids, salts and enzymes.
Lack of iron leads to iron deficiency anemia. It can be treated by iron containing medications.
Zinc is essential element for the proper function of many enzymes and plays an important role in skin regeneration processes, hair and nail growth.
Silver. Silver nitrate denatures protein molecules and has bactericidal and bacteriostatic effect. Such pharmaceutical compositions as collargol and protargol contain silver as highly dispersed colloidal particles of metallic or partically oxidized silver, stabilized by hydrolysated protein (casein, albumin, gelatin). In comparison with ionic silver, colloidal products are less toxic and do not have a cauterizing and irritating effect; they can be considered as a deposited and prolonged form of ionic silver.
Physical and physico-chemical properties
Physical and physicochemical properties of active pharmaceutical ingredients containing metal are given in the Table 4.1.
Table 4.1. Properties of drug substances containing bismuth, zinc, silver and iron
| Chemical formula | Appearance |
| Bismuth subnitrate Bismuthisubnitras Bismuth nitrate basic Bi6O5(OH)3(NO3)5 · 3H2O Contains not less than 79.0% and not more than 82.0% of bismuth Bi2O3 (dried substance) | White or almost white amorphous powder, hygroscopic It dissolves in nitric and 25% hydrochloric acids with decomposition, practically insoluble in water and 96 percent alcohol and chloroform. The powder moistened with water turns blue litmus paper red. It has gastroprotective action, enveloping, astringent, anti-inflammatory effects. Is included into such pharmaceutical compositions like Vikalin, Vikair and number of others |
Zinc sulfate heptahydrate Zinci sulfas heptahydricus &hide_Cookie=yes) ZnSO4 · 7H2O M.m. 287.54 Contains not less than 99.5% and not more than 102.0% of zinc sulfate heptahydrate | Colorless transparent crystals or fine crystalline powder, efflorescent. in air. The aqueous solution is acidic. Very soluble in water, soluble (slowly) in glycerin, practically insoluble in 96 percent alcohol. Has antiseptic, anti-inflammatory, astringent, irritant, cauterizing, emetic effects. It is included into eye drops, suppository Relief Ultra, Anusol and other. It is included into vitamin compositions, e.g., Complivit, Centrum, etc. |
| Zinc oxide Zinci oxidum ZnO ZnO M.m. 81.41 Contains not less than 99.0% of zinc oxide on ignited substance | White or faintly yellowish, amorphous, odorless powder; absorbs carbon dioxide from air;freely soluble in acetic acid diluted 30%, soluble in diluted mineral acids, practically insoluble in water and 96 percent alcohol. Included into such pharmaceutical compositions as Teymur paste, baby powder, zinc ointment, zinc magma (Cindol). Drying, antiseptic, anti-inflammatory |
Silver nitrate Argentinitras &hide_Cookie=yes) AgNO3 M.m. 169.87 Contains not less than 99.75% of silver nitrate | White or almost white, crystalline powder or transparent, colorless crystals, odorless; it darkens on exposure to light; very soluble in water, soluble or slightly soluble in 96 percent alcohol. It has bactericidal, antiseptic, astringent, cauterizing effect |
| Chemical formula | Appearance |
| Protargol. Protargolum (Argentum proteinicum) Contains not less than 7.5% and not more 8.5% of silver | A brownish yellow or brown light amorphous powder, odorless; freely soluble in water, practically insoluble in 96 percent alcohol, ether and chloroform; hygroscopic. It has antiseptic, anti-inflammatory, astringent effect |
| Collargol. Collargolum (Argentum colloidale) Contains not less than 70.0 % of silver | Greenish or bluish-black metallic shiny plates; soluble in water, forms a colloidal solution. Colloidal sol (1:2000) has a yellowish or reddish-brown color, transparent in transmitted light and slightly opalescent in reflected light. It has an antiseptic, anti-inflammatory, astringent effect |
| Ferrous sulfate heptahydrate Ferri (II) sulfas heptahydricus FeSO4 · 7H2O M.m. 278.03 Contains not less than 99.0% and not more than 101.0% | Prismatic transparent bluish-green crystals or crystalline pale green powder; freely soluble in water, practically insoluble in alcohol 96 percent alcohol, efflorescent in air. The aqueous solution is acidic. It is a part of many complex iron pharmaceutical preparations: Fenuls, Ferrogradument, Ferroplex, Aktferrin, etc., used in case of iron deficiency anemia |
Active pharmaceutical ingredients (APIs) of this group are stored in an airtight container with a ground stopper to avoid the crystalline hydrates efflorescence (zinc sulfate, ferrous sulfate) or carbon dioxide absorption (zinc oxide).