Bayamectin 1%

Indications

• Onchocerciasis (river blindness)
• Strongyloidiasis
• Scabies (especially hyperkeratotic or crusted scabies)
• Lymphatic filariasis
• Other helminth infections

Dosage

Children: Child 6 months–17 years: 100 mg for 1 dose;

Adults: Adult: Initially 1 mg/kg daily on the first day, then increased to 6 mg/kg daily in divided doses, gradually increased over 3 days. Maximum 9 mg/kg per day. For scabies, 100 mg for 1 dose; if reinfection occurs, a second dose may be given after 2 weeks.

Mechanism of action

Ivermectin binds selectively to glutamate-gated chloride channels, leading to increased permeability of the cell membrane to chloride ions. This results in hyperpolarization of the nerve or muscle cells in the parasites, causing paralysis and death. It also interacts with other chloride channels, which may contribute to its antiparasitic effects.

Pharmacodynamics

Ivermectin exhibits broad-spectrum activity against a variety of parasites, including nematodes and arthropods. Its effectiveness is attributed to its ability to paralyze and kill parasites, thus facilitating their expulsion from the host. The drug has a long half-life, allowing for effective dosing regimens, and it is generally well-tolerated in patients.

Pharmacokinetics

Ivermectin is rapidly absorbed following oral administration, with peak plasma concentrations occurring within 4 to 6 hours. It is extensively distributed throughout the body, including the central nervous system. The drug undergoes hepatic metabolism, primarily via cytochrome P450, and is eliminated with a half-life of approximately 18 hours. Excretion occurs mainly in the feces, with a smaller proportion eliminated in urine.

Contra-indications

• Blood disorders
• Epilepsy
• Sjögren’s syndrome

Adverse effects

• Diarrhoea
• Dizziness
• Headache
• Influenza-like illness
• Insomnia
• Myalgia
• Nausea
• Rash
• Seizure
• Taste alteration
• Vomiting
• Skin reactions
• Abnormal sensation in eye
• Anaemia
• Appetite decrease
• Asthenia
• Asthma exacerbated
• Chest discomfort
• Confusion
• Conjunctival haemorrhage
• Constipation
• Gastrointestinal discomfort
• Headache
• Hepatitis
• Hypotension
• Joint disorders
• Leukopenia
• Myalgia
• Nausea
• Oedema
• Pain
• Psychiatric disorder
• Severe cutaneous adverse reactions
• Stupor
• Tachycardia
• Tremor
• Urinary incontinence
• Vertigo

Interactions

• Coumarins: Unknown (increases anticoagulant effect)
• Levamisole: Unknown (increases exposure)

Precautions

• Use with caution in hepatic impairment
• Avoid sun exposure when using topical formulations

Pregnancy

Embryotoxic in animal studies, avoid if possible.

Breast-feeding

Manufacturer advises avoid-limited information available; ensure infant does not come in contact with treated areas.

Storage

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

Formulations

• Tablets
• Topical formulation

Indications

• Constipation
• Bowel cleansing

Dosage

Children: Child 1–11 months: 1 g as required, Child 1–11 years: 2 g as required, Child 12–17 years: 4 g as required.

Adults: 4 g as required, usually administered rectally.

Mechanism of action

When administered rectally, glycerol exerts a hygroscopic and/or local irritant action, drawing water from the tissues into the feces and reflexively stimulating evacuation. It decreases intraocular pressure by creating an osmotic gradient between the blood and intraocular fluid, causing fluid to move from the aqueous and vitreous humors into the bloodstream. Glycerol is classified as a hyperosmotic laxative and may also have lubricating and fecal softening effects.

Pharmacodynamics

Glycerol is commonly classified as an osmotic laxative, acting through its local irritant effects and possibly having lubricating and fecal softening actions. Glycerol suppositories usually produce effects within 15 to 30 minutes, providing quick relief from constipation.

Pharmacokinetics

Glycerol is rapidly absorbed through the gastrointestinal tract. It is metabolized in the liver and other tissues, with a half-life that varies depending on the route of administration. Following rectal administration, glycerol is primarily excreted in urine. The pharmacokinetics may vary based on dosage forms and individual patient factors.

Contra-indications

• Acute abdominal conditions
• Acute inflammatory bowel disease
• Intestinal obstruction
• Severe dehydration

Adverse effects

• Abdominal cramps
• Asthenia
• Gastrointestinal disorders
• Hypermagnesaemia
• Skin reactions
• Urine discolouration

Precautions

• Avoid prolonged contact with skin, especially in incontinent patients or infants wearing nappies due to the risk of irritation and excoriation.
• Excessive use may cause diarrhea and related effects such as hypokalaemia.

Pregnancy

Manufacturers advise avoidance due to limited information available.

Breast-feeding

Manufacturers advise avoidance as there is no information available.

Storage

Store at room temperature, away from direct sunlight.

Formulations

• Glycerol 1g suppositories
• Glycerol 2g suppositories
• Glycerol 4g suppositories
• Glycerol oral suspension

Indications

• Disinfectant
• Preservative
• Sterilization of medical instruments
• Formalin for histology and pathology specimens

Dosage

Children: Refer to local guidelines and recommendations, as doses may vary based on the specific clinical situation and formulation used.

Adults: Refer to local guidelines and recommendations, as doses may vary based on the specific clinical situation and formulation used.

Mechanism of action

Formaldehyde acts primarily as a cross-linking agent, covalently binding to proteins and nucleic acids. This mechanism is responsible for its effectiveness as a preservative and disinfectant, as it disrupts cellular metabolism and integrity in microorganisms, leading to cell death.

Pharmacodynamics

The pharmacodynamics of formaldehyde involves its ability to inactivate proteins and DNA through cross-linking, which interferes with cellular functions. This action results in its antimicrobial and preservative effects, although it also contributes to toxicity. The compound can elicit inflammatory responses in tissues and has been associated with respiratory irritations and carcinogenic effects upon prolonged exposure.

Pharmacokinetics

Formaldehyde is rapidly absorbed via inhalation and dermal routes, and it is metabolized mainly by the enzyme formaldehyde dehydrogenase to formic acid, which is then converted to carbon dioxide and water. The elimination half-life in the body is relatively short due to its rapid metabolism. Formaldehyde is distributed widely in body tissues, but due to its reactivity, it does not accumulate significantly.

Pregnancy

Safety in pregnancy has not been established.

Breast-feeding

It is unknown whether this drug is excreted in human milk.

Storage

Store at room temperature, away from moisture and heat.

Dosage

Children: Refer to the BNF for Children for appropriate dosing information in paediatric cases, especially in instances of overdose.

Adults: Refer to the BNF for specific dosing information based on clinical circumstances, particularly in cases of overdose.

Mechanism of action

Ethylene glycol is metabolized by alcohol dehydrogenase to glycoaldehyde, which is subsequently converted to glycolic, glyoxylic, and oxalic acids. These metabolites contribute to anion gap metabolic acidosis and are responsible for tissue injury through the formation of insoluble calcium oxalate crystals.

Pharmacodynamics

The toxicity of ethylene glycol arises from its metabolites, particularly glycolic and oxalic acids. These compounds induce metabolic acidosis, lead to renal failure through calcium oxalate crystal deposition in the kidneys, and can cause neurological impairment. The anion gap increases due to the accumulation of these acids, leading to complications such as cardiovascular instability and potential multi-organ failure.

Pharmacokinetics

Ethylene glycol is rapidly absorbed after oral ingestion. It undergoes first-pass metabolism primarily in the liver, where it is converted into its toxic metabolites. The elimination half-life of ethylene glycol varies but is generally prolonged in cases of renal impairment. Renal excretion of metabolites contributes to the duration of toxicity, necessitating prompt medical intervention in cases of overdose.

Adverse effects

• Metabolic acidosis
• Renal failure
• CNS depression
• Hypocalcemia
• Cardiovascular collapse
• Pulmonary edema

Precautions

• Use with caution in patients with renal impairment
• Monitor for signs of metabolic acidosis
• Evaluate electrolyte levels, particularly calcium

Pregnancy

There is limited data on the safety of ethylene glycol in pregnancy. It should only be used if clearly needed.

Breast-feeding

It is unknown if ethylene glycol is excreted in human milk. Caution is advised.

Storage

Store in a tightly closed container at room temperature, away from heat and moisture.

Formulations

• Liquid

Indications

• Plant growth regulation
• Agricultural applications as a growth inhibitor

Dosage

Children: Not applicable.

Adults: Refer to the relevant agricultural guidelines for specific applications.

Mechanism of action

In an in vitro study, propylene acts as a plant growth inhibitor by inhibiting the oxidation of indole-3-acetic acid by peroxidase in the presence of superoxide anion radicals. This inhibition is linked to the activation of an iron complex (compound III) shuttle, which enhances the reaction rate between superoxide and peroxidase, ultimately affecting plant growth processes. Propylene is a less effective inhibitor compared to ethylene.

Pharmacodynamics

The pharmacodynamic effects of propylene are primarily observed in its role as a growth inhibitor in plants. By modulating the oxidation of phytohormones like indole-3-acetic acid, propylene can influence various growth responses in plants, potentially affecting processes such as cell elongation and division.

Pharmacokinetics

Information on the pharmacokinetics of propylene in humans is not well-documented, as its primary uses are industrial and agricultural. Its metabolism may be influenced by environmental factors, and its effects are primarily studied in the context of plant biology rather than human pharmacology.

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

Ethylene glycol is metabolized by alcohol dehydrogenase to glycoaldehyde, which is then metabolized to glycolic, glyoxylic, and oxalic acids. These acids, along with excess lactic acid are responsible for the anion gap metabolic acidosis. Oxalic acid readily precipitates with calcium to form insoluble calcium oxalate crystals. Tissue injury is caused by widespread deposition of oxalate crystals and the toxic effects of glycolic and glyoxylic acids.

Mechanism of action

In an in vitro study of the mechanism of action of ethylene as a plant growth inhibitor, the effects of ethylene and some of its analogs, including propylene, on the oxidation of indole-3-acetic acid were examined. Ethylene and its analogs inhibited the oxidation of indole-3-acetic acid by peroxidase under conditions where the iron complex (compound III, an oxy-ferrous complex of peroxidase) shuttle was activated. Inhibition occurred only in the presence of the superoxide anion radical 02(-). Spectral and kinetic data indicated that ethylene and its analogs enhanced the rate of reaction of 02(-) with peroxidase; ie, the iron complex (compound III) shuttle, resulting in the formation of compound III. Propylene was a less effective inhibitor than ethylene.