Movicol Paediatric

Indications

• Metabolic acidosis
• Acid-base imbalance
• Urinary alkalinization
• Treatment of certain poisonings
• Cardiac arrest in the context of metabolic acidosis

Dosage

Children: Refer to the BNF for Children for specific pediatric dosages, as they depend on the clinical condition

Adults: Refer to local guidelines and BNF for specific dosing recommendations as they may vary based on clinical condition and severity. General adult dosing for bicarbonate may range from 1 to 2 mEq/kg IV initially, followed by maintenance doses as needed.

Mechanism of action

Bicarbonate acts as a buffer that neutralizes excess acids in the body. It dissociates in solution to produce bicarbonate ions (HCO3-) which can react with hydrogen ions (H+) to form carbonic acid (H2CO3), subsequently leading to the production of carbon dioxide (CO2) and water (H2O). This process helps to raise the pH of the blood and other fluids, counteracting acidosis. Bicarbonate is involved in several metabolic pathways, including the urea cycle and various biosynthetic pathways.

Pharmacodynamics

Bicarbonate's primary pharmacodynamic effect is its ability to buffer hydrogen ions, thus increasing blood pH. This is essential in conditions such as metabolic acidosis, where the body accumulates excess acid. By raising blood pH, bicarbonate can help alleviate symptoms associated with acidemia, such as fatigue, confusion, and shortness of breath. Its effects can also influence the renal and respiratory systems to regulate acid-base homeostasis.

Pharmacokinetics

Bicarbonate is rapidly absorbed from the gastrointestinal tract. It is distributed throughout the body fluids, and its effects can be seen within minutes of administration. The kidneys play a significant role in bicarbonate homeostasis by reabsorbing bicarbonate from urine and excreting hydrogen ions. The elimination half-life can vary, depending on the patient's metabolic state and renal function.

Pregnancy

Use with caution. Consult with a healthcare provider before use.

Breast-feeding

Use with caution. Consult with a healthcare provider before use.

Storage

Store in a cool, dry place away from light.

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 prior to surgical procedures or diagnostic tests

Dosage

Children: Refer to specific guidelines or BNF for Children for dosing information.

Adults: Refer to specific guidelines or BNF for detailed dosing information.

Mechanism of action

Polyethylene glycol works by osmotically retaining water in the intestinal lumen, which increases the water content of the stool. This enhances the passage of stool through the intestines and promotes bowel movements. The high molecular weight of polyethylene glycol prevents its absorption in the gastrointestinal tract, ensuring that it remains in the lumen to exert its effects.

Pharmacodynamics

The pharmacodynamic profile of polyethylene glycol involves its ability to increase stool water content, thereby reducing stool consistency and facilitating easier passage. It does not stimulate intestinal motility directly but rather relies on the osmotic effect to promote bowel evacuation. The onset of action typically occurs within 24 to 96 hours after ingestion.

Pharmacokinetics

Polyethylene glycol is not absorbed systemically, and its pharmacokinetics are characterized by its presence solely in the gastrointestinal tract. It is excreted unchanged in the stool. The volume of polyethylene glycol administered can influence the effectiveness and timing of its action, but its absorption is negligible, making systemic side effects rare.

Adverse effects

• Abdominal cramping
• Diarrhea
• Nausea
• Vomiting
• Bloating
• Flatulence

Precautions

• Use with caution in patients with gastrointestinal disorders or bowel obstruction.
• Ensure adequate hydration during use to prevent dehydration.

Pregnancy

Polyethylene glycol is generally considered safe during pregnancy, but should be used under medical supervision.

Breast-feeding

Polyethylene glycol is excreted in breast milk in very small amounts and is generally regarded as safe during breastfeeding.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Powder for oral solution
• Liquid formulation

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.