GP and patient predictions of sick-listing duration: how well do they correspond? A prospective observational study.

OBJECTIVE: To explore how well physicians and patients predict sick-listing duration and the correspondence between their respective predictions. To study possible gender differences concerning prediction accuracy. DESIGN: Prospective observational study. SETTING: Two medium-sized primary care centres (PCC) in western Sweden. SUBJECTS: GPs at the PCCs and attending patients sick-listed for > 14 days. MAIN OUTCOME MEASURES: Sick-listing duration; patients' and GPs' predictions of the total duration of the individual patient's sick-listing. RESULTS: A total of 127 patients (93 women, 34 men, mean age 45 years) and 10 GPs participated in the study. Neither the GPs nor the patients were able to predict the interval until return to work with high accuracy. The GPs' and the patients' perceptions concurred in only 26% of cases. There was a significant difference in the correspondence between the GPs' and patients' respective predictions of sick-listing duration compared with the actual duration. GPs' predictions were more accurate for medium-length duration (1.5-6 months), while patients' predictions were more accurate for long-duration (> 6 months) sick-listing. Patients with less education predicted long duration of sick-listing more accurately than those with more education. There was no significant difference between male and female patients' accuracy of prediction, or between GPs' accuracy of prediction of male vs. female patients' sick-listing duration. CONCLUSIONS: Prediction of total sick-listing duration was hard for both GP and patient; their respective predictions corresponded in only one-quarter of the cases. No gender differences were observed in the accuracy of prediction.

Cisplatin and oxaliplatin are toxic to cochlear outer hair cells and both target thioredoxin reductase in organ of Corti cultures.

CONCLUSION: Inhibition of thioredoxin reductase (TrxR) may be a contributing factor in cisplatin-induced ototoxicity. Direct exposure of organ of Corti to cisplatin and oxaliplatin gives equal loss of hair cells. OBJECTIVES: Platinum-containing drugs are known to target the anti-oxidant selenoprotein TrxR in cancer cells. Two such anti-cancer, platinum-containing drugs, cisplatin and oxaliplatin, have different side effects. Only cisplatin induces hearing loss, i.e. has an ototoxic side effect that is not seen after treatment with oxaliplatin. The objective of this study was to evaluate if TrxR is a target in the cochlea. Loss of outer hair cells was also compared when cisplatin and oxaliplatin were administered directly to the organ of Corti. METHODS: Organ of Corti cell culture was used for direct exposure to cisplatin and oxaliplatin. Hair cells were evaluated and the level of TrxR was assessed. Immunohistochemical staining for TrxR was performed. An animal model was used to evaluate the effect on TrxR after treatment with cisplatin and oxaliplatin in vivo. RESULTS: Direct exposure of cochlear organotypic cultures to either cisplatin or oxaliplatin induced comparable levels of outer hair cell loss and inhibition of TrxR, demonstrating that both drugs are similarly ototoxic provided that the cochlea becomes directly exposed.

Cochlear pharmacokinetics of cisplatin: an in vivo study in the guinea pig.

OBJECTIVES/HYPOTHESIS: Cisplatin produces toxic lesions to outer hair cells (OHCs) in the cochlear base but not in the apex. The objective of this study was to compare the pharmacokinetic profile of cisplatin in scala tympani (ST) perilymph in the cochlear base and apex, respectively. STUDY DESIGN: In vivo animal study. METHODS: Forty-seven guinea pigs were given an intravenous bolus injection of an ototoxic dose of cisplatin. Ten to 240 minutes after cisplatin was given, blood, cerebrospinal fluid (CSF), and ST perilymph were aspirated within the same target time. ST perilymph was aspirated from the basal turn and from the apex of the cochlea by two different sampling techniques. Liquid chromatography with postcolumn derivatization was used for quantitative determination of the parent drug. RESULTS: Ten minutes after administration, the concentration of cisplatin in ST perilymph was 4-fold higher in the basal turn of the cochlea than in the apex. At 30 minutes, the drug concentrations did not differ. At 60 minutes, the level of cisplatin in ST perilymph and blood UF was equivalent. The perilymph-blood ratio increased thereafter with time. CONCLUSION: The pharmacokinetic findings of an early high concentration of cisplatin in the base of the cochlea and delayed elimination of cisplatin from ST perilymph compared to blood might correlate to the cisplatin-induced loss of OHCs in the base of the cochlea.

Quantitative liquid chromatographic determination of intact cisplatin in blood with microwave-assisted post-column derivatization and UV detection.

The anticancer agent cisplatin (cis-diamminedichloroplatinum(II), cis-[PtCl2(NH3)2]) easily undergoes ligand-exchange reactions, resulting in mainly inactive Pt complexes. This paper presents a method for selective analysis of intact cisplatin in blood using LC and UV detection. Blood samples (hematocrit: 0.22-0.52) were spiked with cisplatin (final concentrations: 2.48 × 10⁻7 M-9.90 × 10⁻6 M) and subjected to centripetal ultrafiltration. The blood ultrafiltrate was separated (loop volume: 5 µl) with a porous graphitic carbon column and a mobile phase of HEPES-buffer (pH 9.3). Prior to UV detection (344 nm), the eluate was mixed with sodium N,N-diethyldithiocarbamate (DDTC) in a microwave field (115 °C) in order to improve the UV absorptivity. Cisplatin eluted as a Pt-DDTC complex after 11.8 min. The peak area was influenced primarily by the hematocrit, the DDTC concentration, and the temperature and residence time in the microwave cavity. The method was robust and sensitive provided preparing a fresh DDTC solution each day and, at the end of a day's run, destroying DDTC remaining in the system. It offers the main advantages of high selectivity, sensitivity, and robustness, minimal sample processing, and the possibility to use small sample volumes.

New insights into the biotransformation and pharmacokinetics of oxaliplatin.

Oxaliplatin is used primarily in the treatment of metastatic colorectal cancer. In this minireview, we discuss potentially important biotransformation pathways in light of its short elimination half-life in vivo. We also highlight new information achieved using a selective analytical technique to measure intact oxaliplatin in pharmacokinetic studies (comprising intravenous, intraperitoneal, and intrahepatic administration) and compare to results obtained by measurements of total platinum. The use of selective analytical techniques is strongly recommended giving kinetic parameters of the parent compound and not only to a complex mixture of platinum containing endogenous compounds.

Cisplatin and oxaliplatin toxicity: importance of cochlear kinetics as a determinant for ototoxicity.

BACKGROUND: Cisplatin is a cornerstone anticancer drug with pronounced ototoxicity, whereas oxaliplatin, a platinum derivative with a different clinical profile, is rarely ototoxic. This difference has not been explained. METHODS: In HCT-116 cells, cisplatin (20 microM)-induced apoptosis was reduced by a calcium chelator from 9.9-fold induction (95% confidence interval [CI] = 8.1- to 11.7-fold), to 3.1-fold induction (95% CI = 2.0- to 4.2-fold) and by superoxide scavenging from 9.3-fold (95% CI = 8.8- to 9.8-fold), to 5.1-fold (95% CI = 4.4- to 5.8-fold). A guinea pig model (n = 23) was used to examine pharmacokinetics. Drug concentrations were determined by liquid chromatography with post-column derivatization. The total platinum concentration in cochlear tissue was determined by inductively coupled plasma mass spectrometry. Drug pharmacokinetics was assessed by determining the area under the concentration-time curve (AUC). Statistical tests were two-sided. RESULTS: In HCT-116 cells, cisplatin (20 microM)-induced apoptosis was reduced by a calcium chelator from 9.9-fold induction (95% confidence interval [CI] = 8.1- to 11.7-fold to 3.1-fold induction) (95% CI = 2.0- to 4.2-fold) and by superoxide scavenging (from 9.3-fold, 95% CI = 8.8- to 9.8-fold, to 5.1-fold, 95% CI = 4.4- to 5.8-fold). Oxaliplatin (20 microM)-induced apoptosis was unaffected by calcium chelation (from 7.1- to 6.2-fold induction) and by superoxide scavenging (from 5.9- to 5.6-fold induction). In guinea pig cochlea, total platinum concentration (0.12 vs 0.63 microg/kg, respectively, P = .008) and perilymphatic drug concentrations (238 vs 515 microM x minute, respectively, P < .001) were lower after intravenous oxaliplatin treatment (16.6 mg/kg) than after equimolar cisplatin treatment (12.5 mg/kg). However, after a non-ototoxic cisplatin dose (5 mg/kg) or the same oxaliplatin dose (16.6 mg/kg), the AUC for perilymphatic concentrations was similar, indicating that the two drugs have different cochlear pharmacokinetics. CONCLUSION: Cisplatin- but not oxaliplatin-induced apoptosis involved superoxide-related pathways. Lower cochlear uptake of oxaliplatin than cisplatin appears to be a major explanation for its lower ototoxicity.

High concentrations of thiosulfate in scala tympani perilymph after systemic administration in the guinea pig.

CONCLUSION: High concentrations of the antioxidant thiosulfate reach scala tympani perilymph after i.v. administration in the guinea pig. Thiosulfate concentrations in perilymph remain elevated longer than in blood. This warrants further studies on the possibility of obtaining otoprotection by thiosulfate administration several hours before that of cisplatin without compromising the anticancer effect caused by cisplatin inactivation in the blood compartment. OBJECTIVE: Thiosulfate may reduce cisplatin-induced ototoxicity, presumably by oxidative stress relief and formation of inactivate platinum complexes. This study aimed to explore to what extent thiosulfate reaches scala tympani perilymph after systemic administration in the guinea pig. MATERIALS AND METHODS: Scala tympani perilymph (1 microl) was aspirated from the basal turn of each cochlea up to 3 h after thiosulfate administration (103 mg/kg b.w., i.v.). Blood samples were also taken. Thiosulfate was quantified by HPLC and fluorescence detection. RESULTS: Substantial thiosulfate concentrations were found in perilymph. The area under the concentration-time curve for thiosulfate in perilymph and blood was 3100 microMxmin and 6300 microMxmin, respectively. The highest thiosulfate concentrations in perilymph were found at the first sampling at about 10 min. Due to a more rapid elimination from blood, perilymph concentrations exceeded those of blood towards the end of the experiment.

Kinetics of Cisplatin and its monohydrated complex with sulfur-containing compounds designed for local otoprotective administration.

The anticancer drug cisplatin can cause permanent inner ear damage. We have determined the second-order degradation rate constant, k(Nu), of cisplatin and its more toxic monohydrated complex (MHC) in the presence of each of the sulfur-containing nucleophiles N-acetyl-l-cysteine, l-cysteine methyl ester, 1,3-dimethyl-2-thiourea, d-methionine, and thiosulfate, compounds that are under evaluation for local administration to prevent cisplatin-induced ototoxicity. MHC was isolated from a hydrolysis solution of cisplatin using liquid chromatography (LC). The degradations were evaluated by measuring the disappearance of MHC and cisplatin at 37 degrees C and pH 7.4 in the presence of each of the nucleophiles using LC and photometric detection. The k(Nu) of MHC and of cisplatin was 0.044 M(-1)sec(-1) and 0.012 M(-1)sec(-1) with N-acetyl-l-cysteine, 0.24 M(-1)sec(-1) and 0.067 M(-1)sec(-1) with l-cysteine methyl ester, 0.16 M(-1)sec(-1) and 0.074 M(-1)sec(-1) with 1,3-dimethyl-2-thiourea, 0.070 M(-1)sec(-1) and 0.069 M(-1)sec(-1) with d-methionine, and 3.9 M(-1)sec(-1) and 0.091 M(-1)sec(-1) with thiosulfate, respectively. Our results suggest that thiosulfate, as being the strongest nucleophile, is a promising candidate for local application in order to reduce the inner ear content of MHC and cisplatin. However, otoprotection is a multifactorial event, and it remains to be established how important nucleophilicity is for the effectiveness of the protecting agent.

Oxaliplatin degradation in the presence of important biological sulphur-containing compounds and plasma ultrafiltrate.

Oxaliplatin undergoes extensive non-enzymatic chemical transformation in the body. Complexes with sulphur-containing compounds have previously been found in plasma from patients treated with oxaliplatin. We have studied the kinetics for the reactions between oxaliplatin and cysteine, methionine, and glutathione, by determination of the degradation of oxaliplatin using liquid chromatography with UV-detection. We also studied the degradation of oxaliplatin in plasma ultrafiltrate (PUF). For the degradation of oxaliplatin in the presence of glutathione, methionine, and cysteine, the second-order rate constants were 4.7M(-1)min(-1) (95% confidence interval [C.I.], 4.4-5.0M(-1)min(-1)), 5.5M(-1)min(-1) (95% C.I., 5.2-5.7M(-1)min(-1)), and 15M(-1)min(-1) (95% C.I., 14-17M(-1)min(-1)), respectively. The reaction rate was much faster than previously reported kinetics for cisplatin. The degradation rate of oxaliplatin in PUF was biphasic. The rate constant for the first phase varied from 9.5x10(-3) to 0.13min(-1) and for the second phase from (1.7 to 1.8)x10(-3)min(-1) in PUF from five healthy volunteers. The first hours of the degradation of oxaliplatin in PUF are accounted for by the degradation of oxaliplatin in a cocktail of sodium chloride and sulphur-containing compounds at physiological plasma concentrations. In conclusion, the rate of the reaction of oxaliplatin with three sulphur-containing compounds was faster for oxaliplatin than what is previously known for cisplatin. This may be important with respect to differences in the cellular effects of cisplatin and oxaliplatin treatment.

High-dose Cisplatin with amifostine: ototoxicity and pharmacokinetics.

OBJECTIVES/HYPOTHESIS: Ototoxicity is a common side effect of high-dose cisplatin treatment. Thiol-containing chemoprotectors ameliorate cisplatin ototoxicity under experimental conditions. The trial was initiated to test the efficacy of amifostine protection in high-dose cisplatin treatment (125-150 mg/m) for metastatic malignant melanoma, to correlate the ototoxic outcome with cisplatin pharmacokinetics, and to evaluate the importance of using a selective analytical method for the quantification of cisplatin. STUDY DESIGN: Prospective study of 15 patients with stage IV malignant melanoma. METHODS: Clinical follow-up of therapeutic response, pure-tone audiometry, and analysis of cisplatin and its monohydrated complex in blood ultrafiltrate by liquid chromatography with postcolumn derivatization were performed. Ultrafiltered blood platinum was analyzed by inductively coupled plasma mass spectrometry. RESULTS: Ototoxicity and gastrointestinal toxicity were the most prominent side effects. Three patients ultimately required hearing aids. All patients had audiometric changes at one or more frequencies after the second treatment course, and all but one patient reported auditory symptoms. No correlation was found between hearing loss and blood cisplatin pharmacokinetics. Platinum levels determined by inductively coupled plasma mass spectrometry were higher than total platinum levels calculated from cisplatin and monohydrated complex concentrations obtained by liquid chromatography analysis. CONCLUSION: Ototoxicity was unacceptable despite amifostine treatment. Cisplatin pharmacokinetics during the first treatment course were not predictive of hearing loss. Amifostine caused a lowering of dose-normalized area under the concentration-time curve for cisplatin and monohydrated complex. Use of the unselective inductively coupled plasma mass spectrometry analysis leads to an overestimation of active drug. Selective analysis of cisplatin is especially important when evaluating cisplatin pharmacokinetics during chemoprotector treatment.

Oxaliplatin degradation in the presence of chloride: identification and cytotoxicity of the monochloro monooxalato complex.

PURPOSE: To study the degradation of oxaliplatin in chloride media and evaluate the cytotoxicity of oxaliplatin in normal and chloride-deficient medium. METHODS: The products of the reaction of oxaliplatin with chloride were separated on a Hypercarb S column with a mobile phase containing 40% methanol in 0.05 M ammonia and subjected to electrospray ionization mass spectrometry. The cytotoxicity of oxaliplatin in normal and chloride-deficient medium was evaluated by 30-min incubations on human colon adenocarcinoma cells (HT-29). RESULTS: We identified a new intermediate degradation product, the monochloro monooxalato complex ([Pt(dach)oxCl]-) and the final product. the dichloro complex (Pt(dach)Cl2), by liquid chromatography-mass spectrometry. [Pt(dach)oxCl]- was found as the negative ion, M-, at m/z 431, and the positive ion, [M+2H]+, m/z 433. Pt(dach)Cl2 was found as the negative ion, [M-H]-, m/z 377, and the positive ion, [M+NH4]+, m/z 396. The fast initial degradation of oxaliplatin can be coupled to the fast formation of [Pt(dach)oxCl]-. In the cytotoxic assay, the cell survival was not affected by the chloride levels. CONCLUSIONS: [Pt(dach)oxCl]-, a new transformation product of oxaliplatin, has been identified. Its in vitro cytotoxic effect does not appear to exceed that of oxaliplatin.

Liquid chromatographic determination of oxaliplatin in blood using post-column derivatization in a microwave field followed by photometric detection.

Oxaliplatin ([(1R,2R)-1,2-cyclohexanediamine-N,N']oxalato(2-)-O,O'-platinum) is the first platinum drug with significant activity for metastatic colon cancer. The analysis of oxaliplatin has previously almost exclusively been based on the determination of the platinum content in plasma or ultrafiltrate using flameless atomic absorption spectroscopy (FAAS) or inductively coupled plasma mass spectrometry (ICPMS). A new method for quantitative determination of the free fraction of the intact drug in blood ultrafiltrate is presented here. Blood was ultrafiltrated centripetally at 4 degrees C and the ultrafiltrate was analyzed by liquid chromatography. Oxaliplatin was separated on a Hypercarb column using a mobile phase of methanol/succinic acid buffer pH 7.0 (9/1, v/v). Post-column derivatization was performed by adding N,N-diethyldithiocarbamate in methanol and with microwave heating of a Teflon tubing. The derivative was quantified by photometric detection at 344 nm. The coefficient of variation of standard blood samples was 4.9 and 2.5% at 0.100 and 1.00 microg/ml, respectively. The limit of quantitation was 0.04 microg/ml.

Ototoxicity, nephrotoxicity and pharmacokinetics of cisplatin and its monohydrated complex in the guinea pig.

PURPOSE: To evaluate and compare the ototoxicity and nephrotoxicity of cisplatin and cis-diammineaquachloroplatinum(II) ion (monohydrated complex of cisplatin, MHC, formed in vivo by hydrolysis of cisplatin) after their separate administration to guinea pigs. METHODS: A dose of 4 mg/kg body weight of MHC was deemed suitable for the toxicity evaluation after dose titration. Electrophysiological hearing thresholds (auditory brainstem response, ABR), plasma creatinine and weight were measured in three groups of animals before and after receiving MHC 4 mg/kg (0.0141 mmol/kg), cisplatin 4.24 mg/kg (0.0141 mmol/kg, i.e. equimolar dose) or cisplatin 8 mg/kg (0.0267 mmol/kg) as an i.v. bolus injection. Cisplatin and MHC were analysed using liquid chromatography with post-column derivatization. RESULTS: Administration of MHC 4 mg/kg caused a moderate ABR threshold shift, a significant increase in creatinine and a significant weight loss, changes similar to those seen after administration of cisplatin 8 mg/kg. Animals given cisplatin 4.24 mg/kg had a slight increase in creatinine, but had no ABR threshold shift and gained weight during the experiment. The pharmacokinetic parameters of cisplatin and MHC were estimated after administration of cisplatin 4.24 mg/kg and MHC 4 mg/kg. The area under the blood-ultrafiltrate concentration versus time curve (AUC) for cisplatin after administration of MHC 4 mg/kg was 23% (56+/-5.0 micro g.min.ml(-1)) (means+/-SD) of that after administration of cisplatin 4.24 mg/kg (240+/-25 micro g.min.ml(-1)). The AUC for MHC after administration of cisplatin 4.24 mg/kg was 20% (30+/-4.9 micro g.min.ml(-1)) of that after administration of MHC 4 mg/kg (149+/-26 micro g.min.ml(-1)). CONCLUSIONS: MHC 4 mg/kg causes ototoxicity, nephrotoxicity and weight loss when administered to guinea pigs. The toxic effects were similar to those seen after administration of cisplatin 8 mg/kg and higher than those seen after administration of cisplatin 4.24 mg/kg.

Hepatic artery infusion using oxaliplatin in combination with 5-fluorouracil, folinic acid and mitomycin C: oxaliplatin pharmacokinetics and feasibility.

BACKGROUND: Several studies have demonstrated the efficacy of systemic oxaliplatin (Oxa) in combination with 5-fluorouracil (5-FU) and folinic acid (FA) for the treatment of colorectal liver metastases (CRLM). However, nothing is presently known about the pharmacokinetics of Oxa administered via the hepatic artery and only very little about the feasibility and toxicity of Oxa used for hepatic artery infusion (HAI). PATIENTS AND METHODS: We designed a phase II trial using Oxa in combination with 5-FU/FA and mitomycin C (MMC) for HAI treatment of patients with isolated non-resectable CRLM. Oxa (130 mg/m2) was delivered on day (d) 1 as a 120-min infusion followed by FA (140 mg/m2) for 10 min and 5-FU (480 mg/m2) for 120 min from d1 to d5 and MMC (7 mg/m2) for 30 min on d5 every 35 days. For Oxa pharmacokinetics, peripheral venous blood was collected before, during and after arterial infusion. Oxaliplatin was determined by liquid chromatography with post-column derivatization in blood ultra filtrate. RESULTS: A total of 33 HAI cycles were administered to 5 patients with tolerable toxicity, which mainly consisted of grade I and II nausea, vomiting, leucopenia, thrombopenia and abdominal pain. During 4 cycles nausea/vomiting III degree occurred, during 3 cycles diarrhoea and abdominal pain III degree. No neurotoxicity > or = II degree and no catheter occlusion was observed. Staging showed 4 PR and 1 PD. Pharmacokinetic analysis revealed an AUC value of 85.3 micrograms x min/ml after HAI. Recalculating these values with the previously reported AUC value for systemic administration (161 micrograms x min/ml) revealed a liver extraction ratio of 0.47 for Oxa. CONCLUSION: We conclude from our results that Oxa in combination with 5-FU/FA and MMC may be a feasible protocol for HAI treatment without major toxicity, especially avoiding higher grade neurotoxicity. This is probably attributable to the low systemic bioavailability of Oxa.

D-Methionine and cisplatin ototoxicity in the guinea pig: D-methionine influences cisplatin pharmacokinetics.

D-Methionine has recently been advocated as a protectant against cisplatin toxicity. The use of systemic D-methionine as a protector was studied in 58 guinea pigs. Kinetics and distribution of [11CH(3)]D-methionine was analysed by positron emission tomography. Cisplatin and the monohydrated complex of cisplatin was quantified in blood ultrafiltrate using reversed-phase liquid chromatography with post-column derivatisation. Administration of 300 mg/kg of D-methionine caused a 30% decrease in the area under the concentration-time curve (AUC) of cisplatin. The toxic effect of cisplatin was studied after dose adjustment of cisplatin, i.e. with similar cisplatin AUC in the group receiving D-methionine and the saline control group. A significant ototoxic effect, measured as difference in pre- and 96 h post-treatment electrophysiological hearing threshold (auditory brainstem response), was observed at stimulus frequencies of 30 and 20 kHz. There was no difference between the groups in the extent of threshold shift. Quantitative outer hair cell counts showed a similar loss of cells in the two groups. All animals had a significant increase in plasma-creatinine but there was no difference between the groups. The results indicate that protection from cisplatin ototoxicity by systemic D-methionine can be explained by a lowered systemic exposure to the drug.