A five way crossover human volunteer study to compare the pharmacokinetics of paracetamol following oral administration of two commercially available paracetamol tablets and three development tablets containing paracetamol in combination with sodium bicarbonate or calcium carbonate

Rapid identification of potential nonsteroidal anti-inflammatory drug overdose-induced liver toxicity and prediction of follow-up exposure: Integrating bioanalytical and population pharmacokinetic assay

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used drugs that can cause liver toxicity. The aim of this study was to integrate bioanalytical and population pharmacokinetic (PopPK) assay to rapidly screen and quantify the concentrations of NSAIDs in plasma and monitor clinical safety. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantification of acetaminophen (APAP), flurbiprofen (FLB), aspirin (ASP), and ibuprofen (IBP), four commonly used NSAIDs. The PopPK model of the signature toxicant was analyzed based on the published literature. The LC-MS/MS method was successfully validated and applied to determine NSAID concentrations in patient plasma samples. APAP, ASP, and IBP data were best fitted using a one-compartment model, and FLB data were best fitted using a two-compartment model. Bootstrapping and visual predictive checks suggested that a robust and reliable pharmacokinetic model was developed. A fast, simple, and sensitive LC-MS/MS method was developed and validated for determining APAP, FLB, ASP, and IBP in human plasma. Combined with the PopPK model, this method was applied to rapidly analyze the concentrations of NSAIDs in clinical samples from patients presenting to the emergency department with acute liver dysfunction and monitored NSAIDs clinical safety.

Direct visualizing of paracetamol immediate release tablet disintegration in vivo and in vitro

The purpose of the present study was to study tablet disintegration by direct visualization, in vivo and in vitro. Based on literature data, a standard conventional paracetamol (CP) tablet, Panodil®, and a rapidly absorbed paracetamol (RP) tablet, Panodil® Zapp, were chosen as model systems to study tablet disintegration in the human stomach. Based on the obtained in vivo results, an in vitro disintegration method was designed to reproduce the visualized disintegration process occurring in the human stomach. For the clinical study, CP and RP tablets fastened to digital endoscopic camera capsules were administered to fasted human volunteers (n=4). The disintegration time and process were visualized by the real time video recordings, using the endoscopic camera capsule. The average disintegration time was found to be 26 ± 13 min and 10 ± 7 min, for CP (n=4) and RP (n=4) tablets, respectively. It was possible to reproduce the in vivo disintegration data in vitro using a USP 2 dissolution apparatus with 250 mL of viscous Fasted State Simulated Gastric Fluid (vFaSSGF*), simulating the rheological profile of human fasted state gastric fluid following administration of a glass of water. The viscosity of the simulated fasted state gastric fluid was found to have a large impact on the disintegration time of the tested immediate release tablets. Therefore, it is recommended to mimic gastric fluid viscosity during in vitro tablet disintegration studies.

Effect of functional excipients on the dissolution and membrane permeation of furosemide formulated into multiple-unit pellet system (MUPS) tablets

The effect of functional excipients (i.e. chitosan, sodium lauryl sulphate, NaHCO₃, and CaCO₃) formulated in multiple-unit pellet system (MUPS) tablets has been investigated on the dissolution and permeability of furosemide, a BCS class IV compound. Spherical beads were produced and compressed into MUPS tablets. MUPS tablet formulations were evaluated for hardness, disintegration, mass variation, friability, and dissolution (pH 1.2, pH 4.6, and pH 7.4). Ex vivo permeability studies were conducted across excised pig tissues (pyloric antrum and duodenal region) on selected experimental MUPS tablet formulations. Histological analysis was conducted on the tissues after exposure to selected experimental MUPS tablet formulations. Dissolution results in the 0.1 M HCl (pH 1.2) showed the highest effect of the excipients on furosemide release. Dissolution parameters showed increased dissolution of furosemide for the MUPS tablet formulations containing functional excipients: a 4.5-10-fold increase in the AUC values, the %_max showed a 60-70% increase and up to a 19-fold increase in DRi was seen. Permeability results revealed a 2.5-fold higher cumulative percentage transport for selected formulations. The results proved that functional excipients incorporated into beads, compressed into MUPS tablet formulations increased furosemide release as well as permeation across excised intestinal tissues.

COMPARATIVE ANALGESIC EFFECTS OF SINGLE-DOSE PREOPERATIVE ADMINISTRATION OF PARACETAMOL (ACETAMINOPHEN) 500 mg PLUS CODEINE 30 mg AND IBUPROFEN 400 mg ON PAIN AFTER THIRD MOLAR SURGERY

BACKGROUND

Efficacy and rapid onset of postsurgical oral pain relief are critical to improve clinical outcomes and reduce the risk of excessive dosing with analgesic drugs.

PURPOSE

To compare analgesic effects of preoperative administration of paracetamol 500 mg plus codeine 30 mg in single-tablet and effervescent formulation to ibuprofen 400 mg, and placebo in the management of moderate to severe postoperative pain after mandibular third molar surgery.

MATERIALS AND METHODS

One hundred twenty healthy outpatients aged 15-29 years undergoing surgical removal of 1 bony impacted mandibular third molar were enrolled in this, single-center, prospective, randomized, triple-blind parallel-group, placebo-controlled, clinical trial. Study participants were randomly assigned to three treatment arms. According to the concealed allocation, each patient 30 minutes before surgery received paracetamol 500 mg plus codeine 30 mg (group APAP/COD), ibuprofen 400 mg (group IBU) or placebo (group PLA). Rescue therapy allowed in the postoperative period was paracetamol 500 mg plus codeine 30 mg in groups APAP/COD and PLA and ibuprofen 400 mg in group IBU. Patients recorded on Numerical Rating Scale-11 (NRS-11) the pain intensity, total number of postoperative-supplement medications and time of the first intake, until 12-hours after surgery and over extra 2 days, RESULTS: Over postoperative 3 days, patients in the APAP/COD group (2.33 ± 1.99) displayed significantly (P< .001) less pain intensity than IBU (3.43 ± 2.47) and placebo (3.57 ± 2.62) groups. The first-day postoperative pain was significantly (P < .001) higher in group PLA than in groups APAP/COD and IBU, but not between the latter 2 groups. However, at 2 hours postdose, the IBU group displayed average pain intensity lower than APAP/COD group (P> .05). On the next 2 days, pain intensity was significantly (P< .001) lower in group APAP/COD than in groups IBU and PLA but failed to reach statistical significance between groups IBU and PLA. Although the time to the first using rescue therapy was longer (445.88 ± 159.96 minute) in group IBU, compared to groups APAP/COD (392.67 ± 138.90 minutes) and PLA (323.00 ± 143.95 minutes), the number of supplemented tablets was significantly higher in group IBU (2.89 ± 2.13) than in groups APAP/COD (1.24 ± 1.79) (P= .001) and PLA (1.53 ± 1.67) (P = .008). No adverse events were registered for all groups.

CONCLUSIONS

Within the limits of the present study, over postoperative 3 days, a statistically significant intensity pain reduction and decreased rescue therapy consumption were recorded in the paracetamol-codeine group than to ibuprofen group. Nevertheless, lower pain intensity at 2 hours postdose and longer time using rescue therapy was found in the ibuprofen group without statistical significance. No adverse events occurred over the studied period.

A review of emerging technologies enabling improved solid oral dosage form manufacturing and processing

Tablets are the most widely utilized solid oral dosage forms because of the advantages of self-administration, stability, ease of handling, transportation, and good patient compliance. Over time, extensive advances have been made in tableting technology. This review aims to provide an insight about the advances in tablet excipients, manufacturing, analytical techniques and deployment of Quality by Design (QbD). Various excipients offering novel functionalities such as solubility enhancement, super-disintegration, taste masking and drug release modifications have been developed. Furthermore, co-processed multifunctional ready-to-use excipients, particularly for tablet dosage forms, have benefitted manufacturing with shorter processing times. Advances in granulation methods, including moist, thermal adhesion, steam, melt, freeze, foam, reverse wet and pneumatic dry granulation, have been proposed to improve product and process performance. Furthermore, methods for particle engineering including hot melt extrusion, extrusion-spheronization, injection molding, spray drying / congealing, co-precipitation and nanotechnology-based approaches have been employed to produce robust tablet formulations. A wide range of tableting technologies including rapidly disintegrating, matrix, tablet-in-tablet, tablet-in-capsule, multilayer tablets and multiparticulate systems have been developed to achieve customized formulation performance. In addition to conventional invasive characterization methods, novel techniques based on laser, tomography, fluorescence, spectroscopy and acoustic approaches have been developed to assess the physical-mechanical attributes of tablet formulations in a non- or minimally invasive manner. Conventional UV-Visible spectroscopy method has been improved (e.g. fiber-optic probes and UV imaging-based approaches) to efficiently record the dissolution profile of tablet formulations. Numerous modifications in tableting presses have also been made to aid machine product changeover, cleaning, and enhance efficiency and productivity. Various process analytical technologies have been employed to track the formulation properties and critical process parameters. These advances will contribute to a strategy for robust tablet dosage forms with excellent performance attributes.

From the pharmaceutical to the clinical: the case for effervescent paracetamol in pain management. A narrative review

OBJECTIVE

Paracetamol has an established place in the management of mild-to-moderate pain, but has certain limitations, including varying bioavailability, and potential hepatotoxicity if taken in overdose. Effervescent formulations may help to overcome these limitations.

METHODS

Pubmed searches, with no limits on date or language, were conducted in February 2020. Further references were identified from the reference lists of retrieved articles, and from the authors' knowledge of the field.

RESULTS

Effervescent formulations contain an organic acid (usually citric acid) and carbonate or bicarbonate salts (usually sodium bicarbonate). Upon contact with water, these react to form carbon dioxide, which facilitates the disintegration of the tablet and dissolution of the active drug. Moreover, sodium bicarbonate dose-dependently increases gastric emptying, which together with rapid dissolution facilitates drug absorption. In pharmacokinetic studies, effervescent formulations result in faster absorption of paracetamol than conventional oral formulations, and this translates into a faster onset of analgesia in clinical trials. Effervescent paracetamol has a favorable safety profile, with good tolerability. Importantly, the sodium content of some preparations does not appear to increase cardiovascular risk under real world conditions. Effervescent formulations may also offer advantages in terms of ease of administration and palatability.

CONCLUSIONS

Effervescent formulations of paracetamol result in faster drug absorption, and hence more rapid analgesia, than oral tablets, and offer a favorable tolerability and safety profile. The use of such formulations may therefore help to promote appropriate use of paracetamol.

Effect of excipients on oral absorption process according to the different gastrointestinal segments

INTRODUCTION

Excipients are necessary to develop oral dosage forms of any Active Pharmaceutical Ingredient (API). Traditionally, excipients have been considered inactive and inert substances, but, over the years, numerous studies have contradicted this belief. This review focuses on the effect of excipients on the physiological variables affecting oral absorption along the different segments of the gastrointestinal tract. The effect of excipients on the segmental absorption variables are illustrated with examples to help understand the complexity of predicting their in vivo effects.

AREAS COVERED

The effects of excipients on disintegration, solubility and dissolution, transit time, and absorption are analyzed in the context of the different gastrointestinal segments and the physiological factors affecting release and membrane permeation. The experimental techniques used to study excipient effects and their human predictive ability are reviewed.

EXPERT OPINION

The observed effects of excipient in oral absorption process have been characterized in the past, mainly in vitro (i.e. in dissolution studies, in vitro cell culture methods or in situ animal studies). Unfortunately, a clear link with their effects in vivo, i.e. their impact on Cmax or AUC, which need a mechanistic approach is still missing. The information compiled in this review leads to the conclusion that the effect of excipients in API oral absorption and bioavailability is undeniable and shows the need of implementing standardized and reproducible preclinical tools coupled with mechanistic and predictive physiological-based models to improve the current empirical retrospective approach.

Bioavailability of the Common Cold Medicines in Jellies for Oral Administration

Jellies for oral administration have been suggested as alternative dosage forms to conventional tablets for improved palatability and compliances for pediatric and geriatric patients. To evaluate the effect of jelly formulation on the bioavailability of cold medicines, two types of jellies were prepared for a fixed-dose combination of acetaminophen (AAP), chlorpheniramine maleate (CPM), dextromethorphan hydrobromide (DMH), and dl-methylephedrine hydrochloride (MEH). Jelly-S and Jelly-H were fabricated using carrageenan and locust bean gum in the absence and presence of xanthan gum, respectively. In vitro dissolution and in vivo absorption of the four drugs in the jellies were compared with other conventional formulations, a syrup and two types of immediate-release (IR) tablets with different hardness, Tablet-S (15 kPa) and Tablet-H (20 kPa). All the formulations exhibited more than 80% dissolution rate within 2 h even though the syrup, Jelly-S, and Tablet-S showed higher 30-min dissolution compared to Jelly-H and Tablet-H. The dissolution rates from the jellies decreased with increasing pH, which resulted in the slowest dissolution in pH 6.8 compared to the syrup and IR tablets. When administered orally to beagle dogs, all five formulations were determined not to be bioequivalent. However, Jelly-S and Jelly-H showed 0.82-1.05 of the geometric mean ratios (GMRs) of AUC_0-t for all four drugs compared to the syrup suggesting comparable absorption. In two IR tablets, GMRs of AUC_0-t were in a range of 0.55-0.95 indicating a tendency of lower absorption than the syrup and jellies. In conclusion, jelly can be a patient-centered formulation with comparable bioavailability to syrup.

The Role of Functional Excipients in Solid Oral Dosage Forms to Overcome Poor Drug Dissolution and Bioavailability

Many active pharmaceutical ingredients (APIs) exhibit poor solubility and low dissolution rates in aqueous environments such as the luminal fluids of the gastrointestinal tract. The oral bioavailability of these compounds is usually very low as a result of their poor solubility properties. In order to improve the bioavailability of these poorly soluble drugs, formulation strategies have been applied as a means to improve their aqueous solubility and dissolution rates. With respect to formulation approaches, excipients can be incorporated in the formulation to assist in the dissolution process of the drug, or specialized dosage forms can be formulated that improve dissolution rate through various mechanisms. This paper provides an overview of selected excipients (e.g., alkalinizing agents, surfactants and sugars) that can be used in formulations to increase the dissolution rate as well as specialized dosage forms such as self-emulsifying delivery systems and formulation techniques such as inclusion complexes and solid dispersions. These formulation approaches are discussed with available examples with specific reference to positive outcomes in terms of drug solubility and bioavailability enhancement.

Why is the therapeutic effect of acute antimigraine drugs delayed? A review of controlled trials and hypotheses about the delay of effect

In randomised controlled trials (RCTs) of oral drug treatment of migraine attacks, efficacy is evaluated after 2 hours. The effect of oral naratriptan 2.5 mg with a maximum blood concentration (T_max ) at 2 hours increases from 2 to 4 hours in RCTs. To check whether such a delayed effect is also present for other oral antimigraine drugs, we hand-searched the literature for publications on RCTs reporting efficacy. Two triptans, 3 nonsteroidal anti-inflammatory drugs (NSAIDs), a triptan combined with an NSAID and a calcitonin gene-related peptide receptor antagonist were evaluated for their therapeutic gain with determination of time to maximum effect (E_max ). E_max was compared with known T_max from pharmacokinetic studies to estimate the delay to pain-free. The delay in therapeutic gain varied from 1-2 hours for zolmitriptan 5 mg to 7 hours for naproxen 500 mg. An increase in effect from 2 to 4 hours was observed after eletriptan 40 mg, frovatriptan 2.5 mg and lasmiditan 200 mg, and after rizatriptan 10 mg (T_max  = 1 h) from 1 to 2 hours. This strongly indicates a general delay of effect in oral antimigraine drugs. A review of 5 possible effects of triptans on the trigemino-vascular system did not yield a simple explanation for the delay. In addition, E_max for triptans probably depends partly on the rise in plasma levels and not only on its maximum. The most likely explanation for the delay in effect is that a complex antimigraine system with more than 1 site of action is involved.

Robustness of crossover trials against subject drop-out - Examples of perpetually connected designs

When performing a repeated measures experiment, such as a clinical trial, there is a risk of subject drop-out during the experiment. If one or more subjects leave the study prematurely, a situation could arise where the eventual design is disconnected, implying that very few treatment contrasts for both direct effects and carryover effects are estimable. This paper aims to identify experimental conditions where this problem with the eventual design can be avoided. It is shown that in the class of uniformly balanced repeated measurement designs consisting of two or more Latin squares, there are planned designs with the following useful property. Provided that all subjects have completed the first two periods of study, such a design will not be replaced by a disconnected eventual design due to drop-out, irrespective of the type of drop-out behaviour that may occur. Designs with this property are referred to as perpetually connected. These experimental conditions are identified and examined in the paper and an example of at least one perpetually connected uniformly balanced repeated measurement design is given in each case. The results improve upon previous contributions in the literature that have been confined largely to cases in which drop-out occurs only in the final periods of study.

A Comparative Study on Dissolution Enhancement of Acetaminophen by Cooling, Anti-solvent, and Solvent Evaporation Crystallization

The aim of this study was to prepare APAP crystals by cooling, anti-solvent, and solvent evaporation crystallization to enhance its dissolution rate and to make comparisons of the three methods. Agitating speeds and types were regarded as factors affecting crystallization procedure. Samples were made with different ratios of PEG4000. They were characterized by X-ray diffraction and scanning electron microscopy. Dissolution tests were conducted to assess their dissolution property. The proportions of carriers existing in crystals by cooling and anti-solvent crystallization ranged from 1.3 to 5.1%. Mean dissolution time (MDT) of samples by the two methods was about 3 min, which was 17.2 min for untreated APAP. Addition of too much PEG4000 in solvent evaporation crystallization could decrease dissolution rate of APAP. Samples agitated by a rotor with speed of 100, 500, and 1000 rpm dissolved faster than those by a high shear mixer with speed of 3400 and 5000 rpm or by a glass rod. Agitating speed and type could affect particle size and drug dissolution. Dissolution enhancement of APAP might be attributed to decrease of fine particles and increase of particle wettability.

Does a hot drink provide faster absorption of paracetamol than a tablet? A pharmacoscintigraphic study in healthy male volunteers

PURPOSE

To investigate the hypothesis that paracetamol is absorbed faster from a hot drink than from a standard tablet using simultaneous scintigraphic imaging and pharmacokinetic sampling.

METHODS

Twenty-five healthy male volunteers received both paracetamol formulations in a randomised manner. The formulation administered in the first treatment arm was radiolabelled to allow scintigraphic monitoring. In both treatment arms, blood samples were taken for assessing paracetamol absorption.

RESULTS

Following the hot drink, paracetamol absorption was both significantly faster and greater over the first 60 min post-dose compared with the tablet, as evidenced by the median time to reach t0.25 μg/mL of 4.6 and 23.1 min, respectively, and AUC0-60 of 4668.00 and 1331.17 h*ng/mL, respectively. In addition, tmax was significantly shorter for the hot drink (median time = 1.50 h) compared with the tablet (1.99 h). However, Cmax was significantly greater following the tablet (9,077 ng/mL) compared with the hot drink (8,062 ng/mL). Onset of gastric emptying after the hot drink was significantly faster than after the standard tablet (7.9 versus 54.2 min), as confirmed scintigraphically.

CONCLUSIONS

Compared with a standard tablet, a hot drink provides faster absorption of paracetamol potentially due to more rapid gastric emptying.

Efficacy and speed of onset of pain relief of fast-dissolving paracetamol on postsurgical dental pain: two randomized, single-dose, double-blind, placebo-controlled clinical studies

BACKGROUND

Paracetamol (APAP), also known as acetaminophen, is the most commonly used over-the-counter analgesic for the treatment of mild-to-moderate pain. However, the speed of onset of pain relief is limited mainly to the standard, immediate-release formulation. Efficacy and speed of onset of pain relief are critical in acute pain situations such as postsurgical dental pain, because reducing pain can improve clinical outcome and reduce the risk of transition from acute pain to more chronic pain. Efficacy and rapid onset also reduce the risk of excessive dosing with the analgesic.

OBJECTIVE

We sought to investigate the dose-response efficacy and speed of onset of pain relief of a fast-dissolving APAP formulation compared with lower doses of APAP and placebo in dental patients after impacted third molar extraction.

METHODS

Two single-center, single-dose, randomized, placebo-controlled, double-blind, double-dummy, parallel-group studies (Study I and Study II) were conducted to evaluate the efficacy and speed of onset of pain relief of different doses of a fast-dissolving APAP tablet (FD-APAP), standard APAP, and placebo in patients with postsurgical dental pain following third molar extraction. In Study I, a single dose of FD-APAP 1000 mg, FD-APAP 500 mg, or placebo was given to 300 patients; in Study II, a single dose of FD-APAP 1000 mg, standard APAP 650 mg, or placebo was given to 401 patients. All 701 patients from both studies were included in the analysis and safety assessment.

RESULTS

FD-APAP 1000 mg demonstrated significantly greater effect compared with FD-APAP 500 mg, APAP 650 mg, and placebo for all efficacy measurements, including sum of pain relief and pain intensity difference, total pain relief, sum of pain intensity difference, pain intensity difference, and pain relief score during 6 hours after the dose. Onset of confirmed first perceptible relief in subjects treated with FD-APAP 1000 mg was 15 minutes, which was 32% and 25% significantly shorter than onset of pain relief of FD-APAP 500 mg (22 minutes) and standard APAP 650 mg (20 minutes), respectively. FD-APAP 500 mg and APAP 650 mg demonstrated efficacy over placebo for most of the measurements; however, their effects were significantly lower and lasted for a shorter period of time than for FD-APAP 1000 mg. All study treatments were well tolerated.

CONCLUSIONS

FD-APAP 1000 mg tablets demonstrated efficacy over placebo. Also, FD-APAP 1000 mg had significantly superior effect, faster onset, and longer duration of pain relief compared with FD-APAP 500 mg and APAP 650 mg tablets.

Intravenous paracetamol: a review of efficacy and safety in therapeutic use

Paracetamol is well established as a leading nonprescription antipyretic analgesic drug and is available in oral, rectal or intravenous forms. However, except for oral paracetamol, there is a marked discrepancy between the extent to which paracetamol is used and the available evidence for an analgesic effect in postoperative pain. This review mainly focuses on intravenous paracetamol. Its efficacy and safety are analyzed, as well as its use in therapeutics, alone or in combination. The morphine-sparing, additive and antihyperalgesia effects of intravenous paracetamol are also reviewed. The analyses are divided into several sections, comparing the efficacy of intravenous paracetamol with placebo, other forms of paracetamol or analgesic agents and analyzing its efficacy in multimodal therapy combined with NSAIDs or a morphinic agent.

Biowaiver monographs for immediate release solid oral dosage forms: Acetaminophen (paracetamol)

Literature data are reviewed on the properties of acetaminophen (paracetamol) related to the biopharmaceutics classification system (BCS). According to the current BCS criteria, acetaminophen is BCS Class III compound. Differences in composition seldom, if ever, have an effect on the extent of absorption. However, some studies show differences in rate of absorption between brands and formulations. In particular, sodium bicarbonate, present in some drug products, was reported to give an increase in the rate of absorption, probably caused by an effect on gastric emptying. In view of Marketing Authorizations (MAs) given in a number of countries to acetaminophen drug products with rapid onset of action, it is concluded that differences in rate of absorption were considered therapeutically not relevant by the Health Authorities. Moreover, in view of its therapeutic use, its wide therapeutic index and its uncomplicated pharmacokinetic properties, in vitro dissolution data collected according to the relevant Guidances can be safely used for declaring bioequivalence (BE) of two acetaminophen formulations. Therefore, accepting a biowaiver for immediate release (IR) acetaminophen solid oral drug products is considered scientifically justified, if the test product contains only those excipients reported in this paper in their usual amounts and the test product is rapidly dissolving, as well as the test product fulfils the criterion of similarity of dissolution profiles to the reference product.

The influence of excipients on the diffusion of ibuprofen and paracetamol in gastric mucus

The aim of this study was to examine the diffusion of commonly administered analgesics, ibuprofen and paracetamol, through gastric mucus. As ibuprofen and paracetamol are often formulated with alkalising excipients, or are commonly co-administered with antacids that have been demonstrated to alter their absorption, diffusion was also studied in the presence of a range of soluble and insoluble antacids or buffering agents. The effect of pH, which has been demonstrated to modify the properties of mucus, was also studied. Mucus was a significant barrier to diffusion for both drugs, compared to an unstirred aqueous layer with diffusion rates significantly lower in the presence of a mucus barrier for both drugs; ibuprofen diffusion also demonstrated a significant increase in the lag time. Paracetamol diffusion was not significantly affected by addition of any antacid, whereas ibuprofen rates were affected and the diffusion lag time for ibuprofen was significantly reduced in all cases. Isolated increases in pH increased the rate and reduced the lag time for ibuprofen diffusion. It was shown that mucus acts as a passive barrier in the case of paracetamol diffusion, and an interactive barrier to ibuprofen diffusion. Changes in mucus viscosity at different pH values may be responsible for the observed changes in ibuprofen diffusion rate.

Early bioavailability of paracetamol after oral or intravenous administration

BACKGROUND

Paracetamol is a peripherally acting analgesic commonly used in multimodal post-operative pain management to reduce the need for more potent analgesics with their unwanted side-effects. The dose and optimal galenical form for achieving analgesic concentrations is not well defined. The primary aim of this pilot project was to study the early bioavailability for two fixed doses of orally administrated paracetamol and one dose of intravenous propacetamol, all of which were given after minor surgery.

METHODS

Thirty-five patients undergoing day surgery were divided into five groups, seven patients each. Groups received either 1 g of an ordinary paracetamol tablet, 2 g of an ordinary paracetamol tablet, 1 g of a bicarbonate paracetamol tablet, 2 g of a bicarbonate paracetamol tablet or 2 g intravenously of prodrug propacetamol. We studied the plasma concentration of paracetamol during the first 80 min after administration.

RESULTS

Within 40 min, intravenous propacetamol gave a median plasma paracetamol concentration of 85 micromol/l (range 65-161) and decreased thereafter. After oral administration, median plasma paracetamol concentration increased with increasing dose and time, but there were huge inter-individual differences at all time points studied. At 80 min after oral paracetamol the median plasma concentrations were 36 and 129 micromol/l for the 1- and 2-g groups, respectively, with an overall range between 0 and 306 micromol/l.

CONCLUSION

Oral administration of paracetamol as part of multimodal pain management immediately post-operatively resulted in a huge and unpredictable variation in plasma concentration compared with the intravenous administration.

Comparison of the rates of disintegration, gastric emptying, and drug absorption following administration of a new and a conventional paracetamol formulation, using gamma scintigraphy

PURPOSE

To investigate the hypothesis that faster drug absorption from a new paracetamol formulation containing sodium bicarbonate compared to that from a conventional formulation results from a combination of enhanced gastric emptying and disintegration/dissolution.

METHODS

Each formulation was administered in both fasted and fed states to 12 healthy volunteers. Gastric emptying and disintegration times were assessed by gamma scintigraphy, and serum paracetamol concentrations were determined by HPLC.

RESULTS

The mean time to complete disintegration of the new tablets was faster than that for conventional tablets in both fasted (10.2 min vs. 22.5 min) and fed (14.3 min vs. 46.4 min) states, although this difference was statistically significant in the fed state only (p = 0.0053). Mean gastric emptying times for the new tablets, as measured by t50 and t90, were also faster than those for conventional tablets in both fasted (t50 = 22.4 min vs. 47.5 min, t90 = 30.9 min vs. 64.1 min) and fed (t50 = 76.9 min vs. 106.4 min, t90 = 152.7 min vs. 155.5 min) states, although these differences were not statistically significant. Two subjects showed dramatically retarded gastric emptying of the new tablets in the fasted state: if these atypical data are excluded, the differences in both t50 and t90 in the fasted state are significant (p = 0.0110 and 0.0035, respectively). Rate of paracetamol absorption reflected the gastric emptying profiles as shown by significant correlation of emptying times with partial AUC.

CONCLUSIONS

It would seem that a combination of faster disintegration and gastric emptying of the new tablets is responsible for the faster rate of absorption of paracetamol from PA compared to P observed in both this study and in previous studies. The differences in gastric emptying are more pronounced in the fasted state, and the differences in disintegration are more pronounced in the fed state.

A new rapidly absorbed paracetamol tablet containing sodium bicarbonate. II. Dissolution studies and in vitro/in vivo correlation

The objective of this study was to compare the in vitro dissolution profile of a new rapidly absorbed paracetamol tablet containing sodium bicarbonate (PS) with that of a conventional paracetamol tablet (P), and to relate these by deconvolution and mapping to in vivo release. The dissolution methods used include the standard procedure described in the USP monograph for paracetamol tablets, employing buffer at pH 5.8 or 0.05 M HCl at stirrer speeds between 10 and 50 rpm. The mapping process was developed and implemented in Microsoft Excel worksheets that iteratively calculated the optimal values of scale and shape factors which linked in vivo time to in vitro time. The in vitro-in vivo correlation (IVIVC) was carried out simultaneously for both formulations to produce common mapping factors. The USP method, using buffer at pH 5.8, demonstrated no difference between the two products. However, using an acidic medium the rate of dissolution of P but not of PS decreased with decreasing stirrer speed. A significant correlation (r = 0.773; p < .00001) was established between in vivo release and in vitro dissolution using the profiles obtained with 0.05 M HCl and a stirrer speed of 30 rpm. The scale factor for optimal simultaneous IVIVC in the fasting state was 2.54 and the shape factor was 0.16; corresponding values for mapping in the fed state were 3.37 and 0.13 (implying a larger in vitro-in vivo time difference but reduced shape difference in the fed state). The current IVIVC explains, in part, the observed in vivo variability of the two products. The approach to mapping may also be extended to different batches of these products, to predict the impact of any changes of in vitro dissolution on in vivo release and plasma drug concentration-time profiles.

A new rapidly absorbed paracetamol tablet containing sodium bicarbonate. I. A four-way crossover study to compare the concentration-time profile of paracetamol from the new paracetamol/sodium bicarbonate tablet and a conventional paracetamol tablet in fed and fasted volunteers

The primary objective of this four-way crossover study was to compare the concentration-time profile of paracetamol from a new rapidly absorbed paracetamol tablet containing sodium bicarbonate (PS) with a conventional paracetamol tablet (P), in a panel of 28 fed and fasted healthy volunteers. The results demonstrated that paracetamol was absorbed more rapidly from tablets containing sodium bicarbonate compared to conventional tablets, as indicated by a shorter tmax in both the fed and fasted state and a higher Cmax in the fasted state. The two formulations were bioequivalent with respect to area under curve (AUC). Food did not affect the extent of absorption from either formulation, as indicated by AUC, however, food did reduce the rate of absorption from both formulations, as indicated by a longer tmax and a lower Cmax. Metabolic activation of paracetamol to its oxidation metabolites, as assessed by combined partial clearances to subsequent secondary metabolites cysteine and mercapturic acid conjugates, indicated that the two formulations were bioequivalent in this respect.