TEARON EYE DROPS

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

• Constipation
• Bowel preparation for surgery or diagnostic procedures

Dosage

Children: Refer to specific guidelines for paediatric dosing, as it varies based on age and clinical condition.

Adults: Refer to specific guidelines for dosing based on the formulation and indication.

Mechanism of action

Polythylene glycol acts as an osmotic agent that draws water into the intestinal lumen through osmosis. This increase in water content softens the stool and increases the frequency of bowel movements. It does not get absorbed or metabolized in the gastrointestinal tract, ensuring that it acts locally within the bowel.

Pharmacodynamics

The osmotic effect of polyethylene glycol leads to an increased intraluminal pressure, stimulating peristalsis and promoting the evacuation of the bowel. The stool becomes softer and easier to pass, alleviating constipation. The onset of action is usually within 1 to 3 days, depending on the dose and individual patient factors.

Pharmacokinetics

Polythylene glycol is not absorbed in the gastrointestinal tract and is excreted unchanged in the feces. The systemic absorption is negligible, which minimizes the risk of systemic side effects. Its action is confined to the lumen of the intestine, making it effective for bowel cleansing and treating constipation.

Contra-indications

• Hypersensitivity to polyethylene glycol or any component of the formulation
• Bowel obstruction
• Severe inflammatory bowel disease
• Ileus

Adverse effects

• Abdominal bloating
• Diarrhea
• Nausea
• Vomiting
• Cramping
• Electrolyte imbalance

Interactions

• May alter absorption of concurrently administered oral medications
• Caution is advised when used with other laxatives

Precautions

• Use with caution in patients with renal impairment
• Monitor electrolytes in patients with prolonged use
• Not recommended for long-term use
• Ensure adequate hydration

Pregnancy

There are no adequate and well-controlled studies in pregnant women. Polyethylene glycol should only be used if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Polyethylene glycol is considered safe during breastfeeding, but it is advisable to use it under medical supervision.

Storage

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

Formulations

• Oral solution
• Powder for oral solution

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

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.