Determination of ibuprofen in human plasma by high-performance liquid chromatography

Inhibitory neurotransmission drives endocannabinoid degradation to promote memory consolidation

Endocannabinoids retrogradely regulate synaptic transmission and their abundance is controlled by the fine balance between endocannabinoid synthesis and degradation. While the common assumption is that “on-demand” release determines endocannabinoid signaling, their rapid degradation is expected to control the temporal profile of endocannabinoid action and may impact neuronal signaling. Here we show that memory formation through fear conditioning selectively accelerates the degradation of endocannabinoids in the cerebellum. Learning induced a lasting increase in GABA release and this was responsible for driving the change in endocannabinoid degradation. Conversely, Gq-DREADD activation of cerebellar Purkinje cells enhanced endocannabinoid signaling and impaired memory consolidation. Our findings identify a previously unappreciated reciprocal interaction between GABA and the endocannabinoid system in which GABA signaling accelerates endocannabinoid degradation, and triggers a form of learning-induced metaplasticity.

Endocannabinoid levels are controlled by the fine balance between their synthesis and degradation. Here, the authors show that memory formation through fear conditioning selectively accelerates the degradation of endocannabinoids in the cerebellum via a lasting increase in GABA release.

Predicting susceptibility and resilience in an animal model of post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a psychiatric disorder whose pathogenesis relies on a maladaptive expression of the memory for a life-threatening experience, characterized by over-consolidation, generalization, and impaired extinction, which are responsible of dramatic changes in arousal, mood, anxiety, and social behavior. Even if subjects experiencing a traumatic event during lifetime all show an acute response to the trauma, only a subset of them (susceptible) ultimately develops PTSD, meanwhile the others (resilient) fully recover after the first acute response. However, the dynamic relationships between the interacting brain circuits that might potentially link trauma-related experiences to the emergence of susceptible and resilient PTSD phenotypes in individuals is not well understood. Toward the first step to reach this goal, we have implemented our experimental PTSD model previously developed, making it suitable to differentiate between susceptible (high responders, HR) and resilient (low responders, LR) rats in terms of over-consolidation, impaired extinction, and social impairment long after trauma. Rats were exposed to five footshocks paired with social isolation. One week after trauma but before extinction, animals were tested in the Open Field and Social Interaction tasks for the identification of a predictive variable to identify susceptible and resilient animals before the possible appearance of a PTSD-like phenotype. Our findings show that exploratory activity after trauma in a novel environment is a very robust variable to predict susceptibility towards a PTSD-like phenotype. This experimental model is thus able to screen and differentiate, before extinction learning and potential therapeutic intervention, susceptible and resilient PTSD-like rats.

Use of ibuprofen to assess inflammatory biomarkers in induced sputum: Implications for clinical trials in cystic fibrosis

BACKGROUND

High-dose ibuprofen (HDI) is a clinically beneficial anti-inflammatory regimen that may be a useful reagent to study induced sputum inflammatory marker changes over short study periods appropriate for early-phase CF clinical trials.

METHODS

We conducted a 28-day, open-label, randomized, controlled trial among 72 clinically stable CF subjects (FEV1≥40% predicted) randomized to HDI or routine care that assessed IL-6, IL-8, TNF-α, IL-1-β, free neutrophil elastase, and white cell counts with differentials change from baseline in induced sputum.

RESULTS

IL-6 was the only biomarker with significant within-group change: 0.13 log10 pg/mL mean reduction among ibuprofen-treated subjects (p=0.04); and no change in the control group. IL-6 change between groups was statistically significant (p=0.024). No other inflammatory biomarker differences were observed between groups after 28 days.

CONCLUSION

Although we studied only one agent, HDI, these results suggest that one month may be inadequate to assess anti-inflammatory candidates using markers from induced sputum.

Semi-fluorinated alkanes as carriers for drug targeting in acute respiratory failure

Partial liquid ventilation (PLV) with perfluorocarbons may cause pulmonary recruitment in acute lung injury (ALI). Semi-fluorinated alkanes (SFAs) provide biochemical properties similar to perfluorocarbons. Additionally, SFAs are characterized by increased lipophilicity. Therefore, SFA-PLV may be considered for deposition of certain therapeutic drugs into atelectatic lung areas. In this experimental study SFA-PLV was evaluated to demonstrate feasibility, pulmonary recruitment, and efficacy of drug deposition. Feasibility of SFA-PLV was determined in pigs with and without experimental ALI. Animals were randomized to PLV with SFAs up to a cumulative amount of 30 mL x kg⁻¹ or to conventional mechanical ventilation. Pulmonary recruitment effects were determined by analyzing ventilation-perfusion distributions. Efficacy of intrapulmonary drug deposition was evaluated in further experiments by measuring drug serum concentrations in the course of PLV with SFA-dissolved α-tocopherol and ibuprofen. Increasing SFA doses caused progressive reduction of intrapulmonary shunt in animals with ALI, indicating pulmonary recruitment. PLV with SFA-dissolved α-tocopherol had no effect on serum levels of α-tocopherol, whereas PLV with SFA-dissolved ibuprofen caused a rapid increase of serum levels of ibuprofen. The authors conclude that SFA-PLV is feasible and causes pulmonary recruitment in ALI. Effectiveness of drug deposition in the lung obviously depends on the partitioning drugs out of the SFA phase into blood.

Clinical effects and toxicokinetic evaluation following massive topiramate ingestion

Topiramate is used to treat a variety of neurologic and psychiatric diseases due to its benign safety profile. Data regarding the toxicity and toxicokinetics of topiramate in acute overdose are limited. A case of massive, acute ingestion resulting in the highest reported topiramate level is presented, including toxicokinetic evaluation. A 37-year-old woman presented with coma unresponsive to naloxone following topiramate ingestion. She had normal vital signs without respiratory depression. She was intubated for airway protection, given 3.5 mg lorazepam IV for facial and neck muscle twitching, and transferred to our facility. No additional sedation was required for 18 h on the ventilator. Following mental status improvement, the patient was extubated. Confusion, dysarthria, and imbalance resolved over the next 2 days. Nonanion gap metabolic acidosis persisted for 3 days. Peak serum topiramate level was 356.6 microg/ml (reference range, 5-20 microg/ml). Massive topiramate ingestion led to prolonged coma with normal vital signs and nonanion gap metabolic acidosis. Coma of this severity has not been previously reported. Serum half-life, which has not been studied after overdose, was 16 h. Despite the large ingestion and significant presenting symptoms, the patient recovered fully with supportive intensive care alone. Massive acute topiramate ingestion may lead to nonanion gap metabolic acidosis and prolonged coma which resolves with intensive supportive care. Toxicokinetic data following large, suicidal ingestion of topiramate were similar to previously published pharmacokinetic information.

Determination of ibuprofen in dog plasma by liquid chromatography and application in pharmacokinetic studies of an ibuprofen prodrug in dogs

A liquid chromatography (LC) method for the determination of ibuprofen in dog plasma is described. Chromatographic separation was performed on a Diamonsil C18 column with a C18 guard column using a binary mixture of acetonitrile and 0.02 mol/l phosphate buffer (pH 6.5) (35:65, v/v) delivered at a flow rate of 1.2 ml/min. The linear range for ibuprofen was from 1.0 to 40.0 microg/ml with a limit of quantitation of 1.0 microg/ml. Within-run accuracy and precision ranged from -0.1% to 4.0% and from 1.1% to 5.5% and between-run accuracy and precision ranged from -1.1% to 4.7% and from 1.3% to 7.0%, respectively. The mean extraction recoveries of ibuprofen determined over the concentrations of 1.0, 10.0, and 40.0 microg/ml were (100.5+/-1.8)%, (99.8+/-1.0)%, and (99.2+/-2.3)%. The developed LC method greatly simplified the sample preparation and adopted mild conditions to prevent the possible hydrolysis of the prodrug and was successfully applied to the pharmacokinetic studies of an ibuprofen prodrug in dogs.

Effect of ibuprofen on neutrophil migration in vivo in cystic fibrosis and healthy subjects

Long-term treatment with ibuprofen twice daily, at doses that achieve peak plasma concentration (Cmax) >50 microg/ml, slows progression of lung disease in patients with cystic fibrosis (CF). Previous data suggest that Cmax >50 microg/ml is associated with a reduction in neutrophil (PMN) migration into the lung and that lower concentrations are associated with an increase in PMN migration. To estimate the threshold concentration at which ibuprofen is associated with a decrease in PMN migration in vivo, we measured the PMN content of oral mucosal washes in 35 healthy (age 19-40 years) and 16 CF (age 18-32 years) subjects who took ibuprofen twice daily for 10 days in doses that achieved Cmax 8 to 90 microg/ml. Cmax >50 microg/ml was associated with a 31 +/- 7% (mean +/- S.E.M.) reduction in PMNs in CF (n = 11, p < 0.001) and 25 +/- 6% reduction in PMNs in healthy subjects (n = 16, p < 0.001). Increasing concentrations above 50 microg/ml was not associated with a greater decrease in PMNs. The reduction in PMN migration was consistently present 12 h after a dose, but not after 24 h. Cmax <50 microg/ml was associated with an increase in PMNs of approximately 40%. These results suggest that Cmax >50 microg/ml and twice daily dosing of ibuprofen are required to decrease PMN migration, and reinforce the current recommendation that pharmacokinetics should be performed in CF patients prescribed ibuprofen.

High-performance liquid chromatography with a column-switching system and capillary electrophoresis for the determination of ibuprofen in plasma

Quantitative aspects of high-performance liquid chromatography with a column-switching system (CSS-HPLC) and capillary electrophoresis (CE) were investigated for the determination of ibuprofen in plasma. For CSS-HPLC, 100 microl of plasma was directly injected onto the column system for the three separation steps: (1) deproteinization and fractionation of plasma samples with a polymer-coated mixed-function phase column, (2) concentration with an intermediate column and (3) final separation with a main column. For CE, a mixture of 50 microl of plasma and 1 ml of acetonitrile was centrifuged and the supernatant was introduced onto the capillary (66 cmX50 microm I.D.; 62 cm to detector) at 20 degrees C. Run buffer was 250 mM sodium borate buffer (pH 8.5) and applied electric field was 379 V cm(-1). Linear dynamic ranges were 0.1-250 microg ml(-1) in CSS-HPLC and 1-1000 microg ml(-1) in CE. Intra-day and inter-day coefficients of variation were less than 5.6% and 6.5% for CSS-HPLC, 6.3% and 6.5% for CE, respectively. The limits of detection (S/N=3) for CSS-HPLC and CE were 25 ng ml(-1) and 300 ng ml(-1), respectively. CSS-HPLC was superior in simplicity and sensitivity, while CE was better in efficiency, rapidity, and cost.

Analysis of ibuprofen in serum by capillary electrophoresis

A rapid method for analysis of the analgesic drug ibuprofen in serum by capillary zone electrophoresis in a borate buffer 160 mmol/l pH 8.5 is described. The method involves deproteinization with acetonitrile to remove serum proteins followed by direct injection on the capillary. The recoveries of standards added to the serum were 84-92%. The method is suited for analysis of samples with concentrations > 10 mg/l. Many other analgesics such as ketoprofen, daypro and salicylates can also be determined by this method.

Determination of ibuprofen in erythrocytes and plasma by high performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method is described for the determination of ibuprofen in isolated erythrocytes and plasma. Before HPLC analysis ibuprofen was isolated by liquid-liquid extraction from these biological matrices; methylene chloride proved to be the best of the organic solvents tested. For the sample of erythrocytes it was necessary to carry out haemolysis prior to their extraction. HPLC was performed on a C-18 column with a mobile phase of methanol-water (220:100, v/v) acidified with perchloric acid to pH 3. Ultraviolet detection was at 222 nm. This method has been applied to the quantification of ibuprofen in rabbit erythrocytes and plasma for a pharmacokinetics study.

Effect of high-dose ibuprofen in patients with cystic fibrosis

BACKGROUND

Since the inflammatory response to chronic infection contributes to lung destruction in patients with cystic fibrosis, we hypothesized that anti-inflammatory therapy might slow the progression of lung disease.

METHODS

In a double-blind trial, 85 patients, 5 to 39 years of age, with mild lung disease (forced expiratory volume in one second [FEV1], > or = 60 percent of the predicted value) were randomly assigned to receive ibuprofen or placebo orally twice daily for four years. Doses were adjusted individually to achieve peak plasma concentrations of 50 to 100 micrograms per milliliter. Changes in pulmonary function, the percentage of ideal body weight, the chest-radiograph score, and the frequency of hospitalization were assessed.

RESULTS

Patients randomly assigned to ibuprofen had a slower annual rate of change in FEV1 than the patients assigned to placebo (mean [+/- SE] slope, -2.17 +/- 0.57 percent vs. -3.60 +/- 0.55 percent in the placebo group; P = 0.02), and weight (as a percentage of ideal body weight) was better maintained in the former group (P = 0.02). Among the patients who took ibuprofen for four years and had at least a 70 percent rate of compliance, the annual rate of change in FEV1 was even slower (-1.48 +/- 0.69 percent vs. -3.57 +/- 0.65 percent in the placebo group, P = 0.03), and this group of patients also had a significantly slower rate of decline in forced vital capacity, the percentage of ideal body weight, and the chest-radiograph score. There was no significant difference between the ibuprofen and placebo groups in the frequency of hospitalization. One patient was withdrawn from the study because of conjunctivitis, and one because of epistaxis related to ibuprofen.

CONCLUSIONS

In patients with cystic fibrosis and mild lung disease, high-dose ibuprofen, taken consistently for four years, significantly slows the progression of the lung disease without serious adverse effects.

High-performance liquid chromatographic assay for ibuprofen in whole blood using solid-phase extraction

A precise, accurate, reproducible one-step method for the high-performance chromatographic determination of ibuprofen in whole blood is described. Samples were, after haemolysis, prepared by solid-phase extraction. Analyses were performed using reversed-phase chromatography on a Separon SGX C18 column with a mobile phase of methanol-water (pH 3) and ultraviolet detection at 222 nm. The method was used for pharmacokinetic studies in rabbits.

High-performance liquid chromatographic determination of naproxen, ibuprofen and diclofenac in plasma and synovial fluid in man

High-performance liquid chromatographic assay procedures have been developed for naproxen, ibuprofen and diclofenac in human plasma and synovial fluid samples. A single liquid-liquid extraction procedure was used to isolate each compound from acidified biological matrix prior to the quantitative analysis. A Spherisorb ODS column (12.5 cm x 4.6 mm I.D.) was used for all the chromatography. Naproxen was eluted with a mobile phase of methanol-Sörensen's buffer at pH 7 (37:63, v/v). Ibuprofen and diclofenac were eluted using mobile phases of methanol-water at pH 3.3 (65:35, v/v and 63:37, v/v, respectively). Diphenylacetic acid was used as the internal standard for the assay of naproxen and flurbiprofen was used in the analysis of ibuprofen and diclofenac. Inter- and intra-day coefficients of variation were less than 7%. The assays were used in clinical studies of the three drugs in osteo- and rheumatoid arthritis patients.

Ibuprofen in children with cystic fibrosis: pharmacokinetics and adverse effects

Antiinflammatory therapy with ibuprofen has been proposed to retard the progression of lund disease in cystic fibrosis (CF). The pharmacokinetics and toxicity of ibuprofen were investigated in a randomized, double-blind, placebo-controlled, 3-month dose-escalation study in 19 children with CF, 6 to 12 years of age. The subjects received orally and twice daily 300 mg of drug during the first month, 400 mg in the second month, and 600 mg in the third month. Ibuprofen pharmacokinetics and evaluation for adverse effects were performed at the beginning and end of each month. The dose of ibuprofen was increased if peak plasma concentration (Cmax) was less than 50 micrograms/ml. To preserve the blind nature of the study, the dose in matched subjects taking placebo was also increased. The subjects randomly assigned to receive ibuprofen (n = 13) completed 26 months of treatment; placebo subjects (n = 5) completed 12 months. With dose escalation, Cmax and the area under the concentration-time curve from zero to infinity significantly increased (p less than 0.01). The pharmacokinetics of ibuprofen in 13 children with CF who received 13.4 +/- 4.1 mg/kg (mean +/- SD) were compared with those in four healthy children who received a similar dose. Peak plasma concentration (48 +/- 17 micrograms/ml) was decreased by 27% (p = 0.06), the area under the concentration-time curve (6.1 +/- 1.7 mg.min/ml) was decreased by 46% (p less than 0.001), apparent total clearance (2.3 +/- 0.6 ml/min.kg-1) was increased by 77% (p less than 0.01), and apparent volume of distribution during terminal phase (291 +/- 91 ml/kg) was increased by 84% (p = 0.01) in the children with CF. Time to Cmax (66 +/- 20 minutes) and elimination half-life (92 +/- 27 minutes) were not significantly different. No subjects were withdrawn from the study because of side effects. No adverse effects could be attributed to ibuprofen. Thus ibuprofen administration has no significant toxic effects, but Cmax will need to be monitored for effective dosing in patients with CF.

Demonstration of the compatibility of narrow-bore packed column high-performance liquid chromatography with conventional detection systems

A number of commercially available high-performance liquid chromatography detectors fitted with conventionally sized flow cells (4.5 to 14 microliters) have been evaluated for use for narrow-bore (1-3 mm i.d.) packed columns. Contrary to the popular misconception, small flow cell volume (and consequently short path length) does not appear to be a prerequisite for successful use of narrow-bore columns. The 1 mm i.d. columns when used with certain detectors gave up to a 17-fold increase in sensitivity, compared with conventional 4.6 mm i.d. columns. This work, which was carried out using conventional injection volumes (50 microliters), shows that narrow-bore HPLC columns can be used in most laboratories to significant advantage without costly conversion of existing equipment.