MIRCERA 50

Indications

• Asthma
• Chronic Obstructive Pulmonary Disease (COPD)
• Hypertension
• Heart Failure
• Cardiac Arrhythmias

Dosage

Children: Refer to the BNF for Children for appropriate dosing

Adults: Refer to the BNF for specific dosing guidelines based on the condition being treated and the formulation of the drug used.

Mechanism of action

Beta-adrenergic agonists stimulate beta-adrenergic receptors, leading to increased intracellular cAMP levels, which causes relaxation of bronchial smooth muscle and dilation of the airways. This mechanism is particularly important in the treatment of asthma and COPD, where airway constriction is a major issue. Beta-blockers, on the other hand, inhibit the effects of catecholamines on beta receptors, resulting in decreased heart rate and myocardial contractility, which is beneficial in managing hypertension and certain types of cardiac arrhythmias.

Pharmacodynamics

The pharmacodynamics of beta drugs vary depending on whether they are agonists or antagonists. Agonists lead to a dose-dependent bronchodilation and increased heart rate, while antagonists decrease heart rate and myocardial oxygen demand. The effects of these drugs can be influenced by patient-specific factors such as receptor sensitivity, presence of comorbid conditions, and concurrent medications.

Pharmacokinetics

The pharmacokinetics of beta drugs can differ substantially. Agonists are typically rapidly absorbed and distributed, with onset of action occurring within minutes. They may have short half-lives, necessitating multiple doses throughout the day. Beta-blockers, in contrast, may have longer half-lives and can be administered once or twice daily. Metabolism usually occurs in the liver, and renal excretion is common for both classes, affecting their dosing in patients with renal impairment.

Interactions

• betablockers, selective + aminophylline: Severe (increases risk of bronchospasm)
• dacomitinib + betablockers, selective: Severe (increases exposure)
• mexiletine + betablockers, selective: Severe (increases risk of cardiovascular adverse effects)
• betablockers, selective + theophylline: Severe (increases risk of bronchospasm)
• beta 2 agonists + linezolid: Severe (increases risk of elevated blood pressure)
• mao-b inhibitors + beta: Severe (increases risk of severe hypertension)
• verapamil + betablockers, non-selective: Severe (increases risk of cardiovascular adverse effects)
• cobicistat + beta: Severe (increases exposure)
• dacomitinib + betablockers, non-selective: Severe (increases exposure)
• idelalisib + beta: Severe (increases exposure)

Indications

• Pain relief in emergency settings
• Procedural sedation
• Anesthesia for minor surgical procedures

Dosage

Children: Refer to the BNF for Children for appropriate dosing information in paediatric patients.

Adults: Refer to the BNF for specific dosage recommendations based on the clinical context and patient factors.

Mechanism of action

Methoxyflurane acts primarily as a central nervous system depressant, enhancing the inhibitory effects of gamma-aminobutyric acid (GABA) at GABA-A receptors. This mechanism contributes to its anesthetic properties by reducing neuronal excitability and promoting sedation. Additionally, methoxyflurane may affect other neurotransmitter systems, including glutamate, but the primary action is through GABA modulation.

Pharmacodynamics

Methoxyflurane provides analgesic and sedative effects through inhalation, rapidly inducing loss of consciousness and analgesia. The drug's potency is influenced by its relatively low MAC (minimum alveolar concentration), which indicates the concentration required to prevent movement in response to surgical stimuli in 50% of patients. The analgesic effect is often noted within minutes of administration, making it suitable for acute pain management.

Pharmacokinetics

Methoxyflurane is characterized by high lipophilicity, leading to rapid absorption into the bloodstream via the lungs. It is quickly distributed throughout body tissues, with a rapid onset of action. The metabolism of methoxyflurane occurs primarily in the liver, and renal excretion is a significant pathway for elimination. Due to its nephrotoxic potential, particularly when used in conjunction with other nephrotoxic agents such as rifampicin, careful consideration of renal function is necessary when prescribing methoxyflurane.

Interactions

• rifampicin+methoxyflurane: Severe (increases risk of nephrotoxicity)

Pregnancy

There is limited data on the use of methoxyflurane in pregnancy. Caution is advised.

Breast-feeding

It is not known whether methoxyflurane is excreted in human milk. Caution is advised.

Storage

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

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