From the Research
Prolonged-release (PR) paracetamol is typically absorbed over 8-12 hours, compared to immediate-release formulations which are absorbed within 30-60 minutes. This extended absorption profile allows PR paracetamol to maintain therapeutic blood levels for a longer duration, reducing the frequency of dosing to twice daily instead of the usual four times daily regimen required with standard paracetamol. The prolonged absorption is achieved through specialized formulation techniques that delay the release of the active ingredient in the gastrointestinal tract. This slower absorption helps provide more consistent pain relief throughout the day and may improve patient compliance due to less frequent dosing. However, it's essential to note that the onset of action is also delayed compared to immediate-release formulations, making PR paracetamol less suitable for situations requiring rapid pain relief.
The total daily dose should not exceed the recommended maximum for paracetamol (typically 4 grams per day for adults), regardless of the formulation used. According to the most recent study 1, a 12-hour sustained-release acetaminophen formulation was evaluated, and the results showed that the time plasma acetaminophen concentration was ≥4 μg/mL was similar to that from two doses of immediate-release acetaminophen.
Key points to consider:
- The absorption time for PR paracetamol is longer than that of immediate-release formulations
- The prolonged absorption profile allows for less frequent dosing
- The total daily dose should not exceed the recommended maximum for paracetamol
- The onset of action is delayed compared to immediate-release formulations
- PR paracetamol may be less suitable for situations requiring rapid pain relief, as seen in studies such as 2, which reported delayed and prolonged absorption of paracetamol in cases of overdose with modified-release paracetamol.
In terms of morbidity, mortality, and quality of life, the use of PR paracetamol can improve patient compliance and provide more consistent pain relief, which can lead to better outcomes and improved quality of life. However, it's crucial to consider the potential risks and benefits of PR paracetamol, particularly in situations where rapid pain relief is required. As noted in 3, the best route of paracetamol administration after major surgery is not known, and further investigation is needed to determine the clinical impact of the differences in plasma concentrations of paracetamol given rectally versus intravenously.