Selection of 12-Hour Sustained-Release Acetaminophen (Paracetamol) Formulation Through Comparison of Pharmacokinetic Profiles of 4 Sustained-Release Prototype Formulations and Standard Acetaminophen Formulation: An Open-Label, Randomized, Proof-of-Principle Pharmacokinetic Study

Prolonged use of paracetamol and the prescribing patterns on rehabilitation facilities

AIMS AND OBJECTIVES

The study investigated: (a) the usage patterns of paracetamol, and (b) the association between paracetamol use and patient outcomes such as liver and kidney functions among older people.

BACKGROUND

Paracetamol is a well-known analgesic and antipyretic drug, with an excellent safety profile when used within its recommended dose. It is a commonly used drug by people aged over 65 years to treat chronic pain. Prolonged use of paracetamol in the elderly is poorly understood. As such, there is a genuine risk among older people of unintentional overdose.

METHODS

A retrospective analysis of medical records in rehabilitation wards was undertaken from 1 July 2016 to 30 June 2017. Patients' paracetamol use, prescribing patterns and biochemical results were analysed to assess for differences in admission and discharge biochemistry results. The TREND Statement was utilised to guide study reporting (Enhancing the QUAlity and Transparency Of health Research, 2021).

RESULTS

A total of 1119 patients were admitted for seven or more days in a metropolitan tertiary hospital in Melbourne. Almost three-quarters (74%) of patients were administered paracetamol; 76.1% received Immediate-Release Paracetamol (IRP), and 23.9% were given Sustained-release paracetamol (SRP). A proportion (4.5%) of patients in both the IRP and SRP groups received more than the daily recommended dose. There were limited statistically significant differences between patients' admission and discharge biochemistry results; group or time differences were observed, which were indicative of improvements within the paracetamol group.

CONCLUSION

Paracetamol was a commonly used medication among long-stay elderly patients. Precaution to ensure paracetamol use does not exceed recommended daily doses is required. This study suggests that paracetamol used at a therapeutic level in older patients had limited, negative associations with liver and kidney function.

RELEVANCE TO CLINICAL PRACTICE

The clinical practice regarding prolonged use of paracetamol is ambitious. The increased risk of paracetamol toxicity among the frail elderly is a concern. Optimising the dose adjustment in the elderly is important to avoid adverse outcomes.

Evaluation of a 12-Hour Sustained-Release Acetaminophen (Paracetamol) Formulation: A Randomized, 3-Way Crossover Pharmacokinetic and Safety Study in Healthy Volunteers

Acetaminophen (paracetamol) is a first-line treatment for mild and moderate pain. A twice-daily sustained-release (SR) formulation may be more convenient for chronic users than standard immediate-release (IR) acetaminophen. This randomized, 3-way crossover study evaluated pharmacokinetics and safety of single-dose 1500- and 2000-mg SR acetaminophen formulations and 2 doses of IR acetaminophen 1000 mg given 6 hours apart in healthy adults (n = 14). Primary outcome was time that plasma acetaminophen concentration was ≥4 μg/mL (TC≥4μg/mL ). Key secondary outcomes were area under the plasma concentration-time curve (AUC) from time 0 to time t, when plasma acetaminophen was detectable (AUC0-t ), AUC from 0 to infinity (AUC0-inf ), and maximum plasma acetaminophen concentration (Cmax ). TC≥4μg/mL from 2000-mg SR acetaminophen was similar to that from 2 doses of IR acetaminophen, whereas TC≥4μg/mL for 1500-mg SR acetaminophen was significantly shorter than that for IR acetaminophen (P = .004). The extent of acetaminophen absorption from 2000-mg SR and 2 doses of the IR formulation was similar and within bioequivalence limits with regard to AUC0-12 , AUC0-t , and AUC0-inf . The extent of acetaminophen absorption from 1500-mg SR was significantly lower than that from IR acetaminophen. The 2000-mg SR represents a potential candidate formulation for 12-hour dosing with acetaminophen.

Bioequivalence and Safety of Twice-Daily Sustained-Release Paracetamol (Acetaminophen) Compared With 3- and 4-Times-Daily Paracetamol: A Repeat-Dose, Crossover Pharmacokinetic Study in Healthy Volunteers

Twice-daily sustained-release (SR) paracetamol (acetaminophen) offers convenient administration to chronic users. This study investigated at steady state (during the last 24 hours of a 3-day dosing period) the pharmacokinetics, bioequivalence, and safety of twice-daily SR paracetamol compared with extended-release (ER) and immediate-release (IR) paracetamol. In this open-label, randomized, multidose, 3-way crossover study, 28 healthy subjects received paracetamol SR (2 × 1000 mg twice daily), ER (2 × 665 mg 3 times daily), and IR (2 × 500 mg 4 times daily). At steady state, twice-daily SR paracetamol was bioequivalent to ER and IR paracetamol. The 90% confidence intervals for the ratios of geometric means were within the acceptance interval for SR/ER paracetamol (AUC_0-t , 0.973-1.033; AUC_0-24 , 0.974-1.034; AUC_0-∞ , 0.948-1.011; C_max , 1.082-1.212; C_av , 1.011-1.106) and SR/IR paracetamol (AUC_0-t , 0.969-1.029; AUC_0-24 , 0.968-1.027; AUC_0-∞ , 0.963-1.026; C_max , 0.902-1.010; C_av , 1.004-1.098). Given twice daily, the SR formulation demonstrated SR properties as expected. Mean time at or above a 4 μg/mL plasma concentration of paracetamol from 2 daily doses of the SR formulation was significantly longer than that from 4 daily doses of IR paracetamol. SR formulation also had a greater T_max , a longer half-life, and lower C_min compared with ER and IR paracetamol. All formulations were well tolerated.