Given the interest and popularity of our Blog post entitled ‘Hyoscine Hydrobromide vs Butylbromide: An Overview’ here at www.pharmascholar.co.uk, I thought to produce a similar overview but this time for Morphine and Oxycodone.
The following piece provides a summary of the two drug substances and offers prescribing hints and tips. I hope you enjoy this latest Blog entry!!
Introduction
Morphine and Oxycodone are two widely used opioid analgesics for managing moderate to severe pain. Understanding their pharmacological differences, indications and prescribing guidelines is crucial for healthcare professionals to optimise pain management whilst minimising risks to the patient.
Pharmacology and Mechanisms of Action
Morphine is a naturally occurring alkaloid derived from the opium poppy, Papaver somniferum. It primarily binds to mu-opioid receptors in the central nervous system, inhibiting neurotransmitters such as substance P and glutamate that are involved in pain signal transmission. The molecular structure of Morphine allows it to interact with other opioid receptor subtypes (e.g. delta and kappa), contributing to its broad side effect profile (e.g. constipation and respiratory depression).
Oxycodone is a semi-synthetic opioid that is synthesised from thebaine, which is another alkaloid found in the opium poppy. This drug also binds to mu-opioid receptors but has modifications that enhance its oral bioavailability and potency. The unique interaction of this drug with opioid receptors offers different therapeutic benefits and side effect profiles compared to Morphine.
Indications for Use
Morphine is often prescribed as the first-line opioid for both cancer and non-cancer pain. It is available in various drug formulations (e.g. immediate-release tablets, extended-release tablets, intravenous injections and rectal suppositories). Morphine is particularly effective for severe pain conditions due to its high efficacy in activating mu-opioid receptors.
Oxycodone is typically used as a second-line opioid when Morphine is ineffective or not tolerated. It is available in immediate-release and extended-release formulations, for example. Oxycodone is twice as potent as Morphine, making it suitable for patients requiring stronger analgesia.
Prescribing Information for Clinicians in the UK
When prescribing opioids, clinicians must consider several factors to ensure safe and effective pain management:
Correct Drug, Dose and Formulation:
Ensure the correct opioid is selected based on the patient's pain severity and response to previous treatments.
Be aware of dose equivalence between different opioids and routes of administration.
Immediate-release (IR) formulations act quickly and can be given 'as required' for breakthrough pain, whilst modified-release (MR) formulations control background pain over a 24-hour period.
Brand Prescribing:
Oxycodone should be prescribed by brand to reduce the risk of administration errors and ensure cost-effective prescribing.
Preferred brands for Oxycodone include Longtec® for prolonged-release preparations and Shortec® for immediate-release capsules and solutions.
Morphine MR preparations should also be prescribed by brand, such as Zomorph® and MST®.
Dose Adjustments:
For patients switching from Morphine to Oxycodone, divide the total daily dose of morphine by 1.5 to 2 to determine the appropriate Oxycodone dose.
Regularly review the patient's pain management plan and adjust doses based on efficacy and side effects.
Monitoring and Safety:
Monitor patients for signs of opioid misuse, addiction plus adverse effects.
Educate patients on the correct use of opioids and the importance of adhering to prescribed doses.
Conclusion
Morphine and Oxycodone are essential drugs in pain management, each with unique pharmacological profiles and indications. Healthcare professionals must carefully consider patient-specific factors and adhere to prescribing guidelines to optimise treatment outcomes and minimise risks. By understanding the differences between these opioids and following best practices, healthcare providers can effectively manage pain while ensuring patient safety.
We hope that you have found this Blog entry helpful. It is information like this that is particularly applicable for the Prescribing Safety Assessment (PSA); please see pharmaPSA for more detail on this. If you have any specific questions or need further details, feel free to ask our lead tutor Dr Mike Davies.
The MST Continus Modified Release Product containing Morphine Sulphate.