ALPHA GLYCERIN AND ICHTHAMMOL

Indications

• Constipation
• Decreased intraocular pressure

Dosage

Children: For children, refer to the BNF for Children for appropriate glycerin dosing guidelines.

Adults: For constipation, glycerin can be administered rectally as a suppository. Follow specific product guidelines for dosage.

Mechanism of action

When administered rectally, glycerine exerts a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexively stimulating evacuation. Additionally, glycerine decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, leading to fluid movement out of the aqueous and vitreous humors into the bloodstream.

Pharmacodynamics

Glycerine is commonly classified as an osmotic laxative but may also exert local irritant effects, lubricating, and fecal softening actions. Its onset of action typically occurs within 15 to 30 minutes when used as a suppository.

Pharmacokinetics

Glycerine is readily absorbed and metabolized in the body. It undergoes glycerol metabolism pathways, contributing to various biochemical processes including phospholipid biosynthesis. The pharmacokinetic profile of glycerine indicates a rapid onset of action due to its osmotic properties.

Adverse effects

• Abdominal cramps
• Diarrhea
• Nausea
• Vomiting
• Electrolyte imbalance

Precautions

• Use with caution in patients with renal impairment
• May cause dehydration if used excessively
• Monitor for electrolyte disturbances in prolonged use

Pregnancy

Glycerin is generally considered safe to use during pregnancy for indicated conditions. Always consult a healthcare provider before use.

Breast-feeding

Glycerin is unlikely to be harmful in breastfeeding mothers. Consult a healthcare provider for specific guidance.

Storage

Store in a cool, dry place, away from direct sunlight. Keep out of reach of children.

Formulations

• Suppositories
• Oral solution

Indications

• Eczema
• Psoriasis
• Chronic lichenified eczema
• Mild inflammatory skin disorders associated with infection

Dosage

Children: Consult product literature for specific dosing recommendations.

Adults: Apply 1–3 times a day to the affected area.

Mechanism of action

Ichthammol works by reducing inflammation and irritation in the skin. It may act by promoting the normalization of skin function and by exerting an anti-inflammatory effect, although the precise mechanism of action is not fully understood. Its keratolytic properties help in the softening and removal of scales and crusts associated with various skin conditions.

Pharmacodynamics

Ichthammol exhibits anti-inflammatory and antiseptic properties, which help in reducing redness, swelling, and discomfort associated with skin conditions. The keratolytic effect promotes the shedding of dry, scaly skin, facilitating the healing process.

Pharmacokinetics

Ichthammol is applied topically, leading to localized effects. Systemic absorption is minimal, and therefore, it is primarily confined to the site of application. The pharmacokinetic profile in humans has not been extensively studied, but the local effects are significant in managing skin conditions.

Pregnancy

Tetracyclines should not be given to pregnant women. Effects on skeletal development have been documented when tetracyclines have been used in the first trimester in animal studies. Administration during the second or third trimester may cause discoloration of the child's teeth.

Breast-feeding

Tetracyclines should not be given to women who are breast-feeding, although absorption and therefore discoloration of teeth in the infant is probably prevented by chelation with calcium in milk.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• Cream
• Ointment

Mechanism of action

When administered rectally, glycerin exerts a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexively stimulating evacuation. Glycerin decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, causing fluid to move out of the aqueous and vitreous humors into the bloodstream. Glycerin (glycerol) and sorbitol are hyperosmotic laxatives. When administered rectally, glycerin and sorbitol exert a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexly stimulating evacuation. The extent to which the simple physical distention of the rectum and the hygroscopic and/or local irritant actions are responsible for the laxative effects of some of these drugs is not known. Only extremely high oral doses of sorbitol (25 g daily) or glycerin exert laxative action. /Glycerin/ decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, causing fluid to move out of the aqueous and vitreous humors into the bloodstream. The physicochemical effects of a series of alkanols, alkanediols and glycerol on erythrocyte shape and hemolysis at 4 and 20 degrees C were examined. We calculated the dielectric constant of the incubation medium, Ds, and the dielectric constant of the erythrocyte membrane Dm in the presence of organic solutes. The ratio Ds/Dm = -38.48 at 20 degrees C defines the normal biconcave shape in a medium without hemolytic agents. A decrease in Ds/Dm favors externalization or internalization with consequent hemolysis. Alkanols and alkanediols convert biconcave erythrocytes into echinocytes, which is accompanied by an increase in the projected surface area. Glycerol converts biconcave erythrocytes into stomatocytes, which was accompanied by a marginal decrease in the projected surface area. Progressive externalization in alkanols and alkanediols or internalization in glycerol resulted in a decrease in the projected surface area and the formation of smooth spheres. The degree of shape change induced was related to the degree of hemolysis and the ratio Ds/Dm. A decrease in temperature reduced both the degree of shape change and hemolysis. .../Thus/ physicochemical toxicity may be a result of a temperature dependent hydrophobic interaction between the organic solutes and the membrane and is best interpreted by the ability of the solutes to change Ds and Dm.

Pharmacodynamics

Glycerin is commonly classified as an osmotic laxative but may act additionally or alternatively through its local irritant effects; it may also have lubricating and fecal softening actions. Glycerin suppositories usually work within 15 to 30 minutes.

Mechanism of action

The precise mechanism by which hydroxyurea produces its antineoplastic effects cannot, at present, be described. However, the reports of various studies in rat and human tissue cultures lend support to the hypothesis that hydroxyurea causes an immediate inhibition of DNA synthesis, by acting as a ribonucleotide reductase inhibitor, without interfering with the synthesis of ribonucleic acid or of protein. Hydroxyurea probably acts by decreasing the rate of conversion of ribonucleotides and deoxyribonucleotides. This effect is particularly apparent in cells with a high rate of proliferation. Particularly, hydroxyurea reduces the tyrosyl free radical at the active site of the M2 via a one-electron transfer reaction through the –NH2-OH moiety. Three mechanisms have been postulated for the potentiation of the therapeutic effects of irradiation by hydroxyurea on squamous cell (epidermoid) carcinomas of the head and neck. In vitro studies utilizing Chinese hamster cells suggest that hydroxyurea is lethal to normally radioresistant S-stage cells and holds other cells of the cell cycle in the G1 or pre-DNA synthesis stage where they are most susceptible to the effects of irradiation. The third mechanism of action has been theorized on the basis of in vitro studies of HeLa cells: it appears that hydroxyurea, by inhibition of DNA synthesis, hinders the normal repair process of cells damaged but not killed by irradiation, thereby decreasing their survival rate; there is no alteration of RNA and protein syntheses. Another proposed mechanism of action of hydroxyurea is the elevation of HbF concentrations in Sickle Cell Disease patients. HbF interferes with the polymerization of HbS (sickle haemoglobin) and thus impedes the sickling of red blood cell. Recently, hydroxyurea has shown to be associated with the generation of nitric oxide, suggesting that nitric oxide stimulates cyclic guanosine monophosphates (cGMP) production, which then activates a protein kinase and increases the production of HbF. Other known pharmacological effects of hydroxycarbamide which may contribute to its beneficial effects in Sickle Cell Disease include decrease of neutrophils, improved deformability of sickled cells, and altered adhesion of red blood cells to the endothelium. The exact mechanism of antineoplastic activity of hydroxyurea has not been fully determined. Some studies indicate that hydroxyurea interferes with the synthesis of DNA without interfering with the synthesis of RNA or protein. Although hydroxyurea may have multiple sites of action, it appears likely that the drug inhibits the incorporation of thymidine into DNA; in addition, it may directly damage DNA. Hydroxyurea can destroy the tyrosyl free radical that is formed as the catalytic center of ribonucleoside diphosphate reductase, the enzyme that catalyzes the reductive conversion of ribonucleotides to deoxyribonucleotides; this conversion is a critical and probably rate-limiting step in the synthesis of DNA. The drug is an S-phase inhibitor and may cause cells to arrest at the G1-S border, decrease the rate of cell progression into the S phase, and/or cause cells to accumulate in the S phase as a result of inhibiting DNA synthesis. Animal studies indicate that the cytotoxic effects of hydroxyurea are limited to those tissues with high rates of cellular proliferation and the effects are evident only in those cells that are actively synthesizing DNA. Hydroxyurea, a drug widely used in therapy of several human diseases, inhibits deoxynucleotide synthesis and, consequently, DNA synthesis by blocking the cellular enzyme ribonucleotide reductase. Hydroxyurea inhibits human immunodeficiency virus type 1 (HIV-1) DNA synthesis in activated peripheral blood lymphocytes by decreasing the amount of intracellular deoxynucleotides, thus suggesting that this drug has an antiviral effect. Hydroxyurea has now been shown to block HIV-1 replication in acutely infected primary human lymphocytes (quiescent and a

Pharmacodynamics

The correlation between hydroxyurea concentrations, reduction of crisis rate, and increase in HbF, is not known.