Spinal versus peripheral effects of adjunct clonidine: comparison of the analgesic effect of a ropivacaine-clonidine mixture when administered as a caudal or ilioinguinal-iliohypogastric nerve blockade for inguinal surgery in children

BACKGROUND

The adjunctive use of clonidine to local anaesthetics has been reported to enhance analgesia both after spinal and peripheral administration. However, no attempt has been made to compare spinal and peripheral application of clonidine in the same surgical context in order to further explore the mechanism for the analgesic action of clonidine when administered together with local anaesthetics.

METHODS

Using a prospective, randomized, observer-blinded study design, 40 patients, aged 1-7 years, who were undergoing elective surgery for inguinal hernia repair or orchidopexy, were randomly allocated to receive either a caudal block (group C: n = 20; ropivacaine 0.2%, 1 ml.kg-1 + clonidine 2 micro g.kg-1) or an ilioinguinal-iliohypogastric nerve block (group I: n = 20; ropivacaine 0.2%, 0.4 ml.kg-1 + clonidine 2 micro g.kg-1) following the induction of a standardized sevoflurane based anaesthetic. Postoperative analgesia [maximum Objective Pain Scale (OPS) score and requirement for supplemental analgesia] and sedation (three-point scale) were assessed at predetermined intervals during the first 24 h postoperatively.

RESULTS

Fourteen children in group I and nine children in group C did not require rescue analgesia (P = 0.17). No difference in maximum OPS scores could be detected between the two study groups. The mean time to full recovery regarding sedation was 149 min and 153 min in groups C and I, respectively.

CONCLUSIONS

This pilot study demonstrates a trend for better postoperative analgesia following peripheral administration of clonidine compared with central application. However, the main mechanism for the adjunct analgesic effect of clonidine when administered together with local anaesthetics requires further study.

Pharmacokinetics of doxorubicin in children with acute lymphoblastic leukemia: multi-institutional collaborative study

BACKGROUND

In adults, it has been shown that the pharmacokinetics of doxorubicin are highly variable, despite standardization of the dose based on body surface area (BSA). The purpose of this study was to determine the plasma concentrations of doxorubicin and its active metabolite doxorubicinol in children treated for acute lymphoblastic leukemia (ALL).

PROCEDURE

Children, 107 in number, aged 1.3-17.3 years, were studied at Day 1 of induction therapy according to the current Nordic protocol. Five infants, 3-9 months old, were also included. Plasma samples were drawn 23 hr after the start of a 24-hr infusion of doxorubicin 40 mg/m(2), and analyzed by reversed-phase liquid chromatography.

RESULTS

There was a more than 10-fold difference between patients in dose normalized plasma concentration of doxorubicin, median 62.8 ng/ml, range 22.6-334 ng/ml. The doxorubicin concentrations differed significantly between age groups (P = 0.003). Children aged 4-6 years had the highest doxorubicin concentrations, median 77.9 ng/ml, followed by 2-4-year-old children, median 64.3 ng/ml. Both younger and older children had median values of about 50 ng/ml. Patients with white blood cell (WBC) count > 50 x 10(9)/L at diagnosis had significantly lower doxorubicin concentrations, median 55.3 ng/ml, than those with WBC count < 10 x 10(9)/L, median 64.4 ng/ml (P = 0.015). There was no difference in doxorubicin concentration between boys and girls. No correlation was found between doxorubicin levels and serum aminotransferases or serum creatinine. The concentration of doxorubicinol was 13% (median value) of that of doxorubicin. Four infants, 7-9 months old, had plasma clearance between 350-431 ml/min/m(2), which is in the same range as in older children. A 3-month-old infant had a clearance of 181 ml/min/m(2).

CONCLUSIONS

The age groups who had the highest doxorubicin concentrations, (2-) 4-6-year-old children, are known to make up a large proportion of standard risk ALL cases with good prognosis. The correlation between doxorubicin plasma levels and clinical effect needs further study. The influence of age, body composition, and tumor burden on the pharmacokinetics of antineoplastic drugs should also be further explored, aiming at improvements in the current dosing regimen based on BSA.

Quantification of doxorubicin in plasma--a comparative study of capillary and venous blood sampling

Doxorubicin, an anthraquinone glycoside, is currently one of the clinically most important antineoplastic drugs. The aim of the present study was to identify potential concentration differences of doxorubicin in plasma from capillary and venous blood samples. Sixteen patients (seven females and nine males; median age: 37 years, range: 1-77 years) were included. The quantitative analysis of doxorubicin was carried out by reversed-phase liquid chromatography with fluorometric detection. The concentration of doxorubicin in capillary and venous samples were closely correlated (r=0.98; p<0.0001). The median plasma concentration ratio capillary/venous was 1.13 (95% confidence interval: 1.06-1.20) and not affected either by plasma drug concentration, age or the body mass index of the patient. The concentration ratio was significantly higher in males (median: 1.18) than in females (median: 1.01). The observed concentration differences of doxorubicin in plasma from capillary and venous samples are of minor importance only. Capillary blood sampling is recommended for use in pharmacokinetic studies of doxorubicin, especially in pediatric patients, in order to avoid sometimes traumatic venous blood sampling.

Amifostine protects against early but not late toxic effects of doxorubicin in infant rats

The improved prognosis and increased expected lifetime among long-term survivors of childhood malignancies have made these patients especially sensitiveto the late toxicity of cancer therapy and prone to secondary malignancies. Recently, new strategies aiming to protect against cancer treatment toxicity have been developed, including the drug amifostine (Ethyol), which is suggested to protect normal tissues from the toxic effects of radiation and cytotoxic agents. In the present study, the possible protective effect of amifostine against toxicity induced by a single injection of doxorubicin (3 mg/kg) in immature rats was evaluated. Specifically, we evaluated the protection against long-term toxicity and the effects of amifostine on growing immature tissues. Amifostine (50-200 mg/kg) given 15 min before doxorubicin had a significant protective effect against doxorubicin-induced early alopecia in young rats. Significant protection against cataract formation was obtained by the use of low-dose amifostine (50 mg/kg). However, amifostine did not protect young rats against the late toxic effect of doxoubicin on linear growth, body weight, plasma leptin levels, and heart or testicular tissue. Worrisome, and in contrast to earlier studies in adult rats, an increased doxorubicin toxicity actually was observed and mortality was increased when the higher doses of amifostine (100-200 mg/kg) were used. The present results suggest that more data from growing immature animal models are needed to analyze the safety of amifostine treatment and its mechanisms of action before wider clinical use of this drug in pediatric cancer patients is recommended.

Pharmacokinetics and pharmacodynamics of NTBC (2-(2-nitro-4-fluoromethylbenzoyl)-1,3-cyclohexanedione) and mesotrione, inhibitors of 4-hydroxyphenyl pyruvate dioxygenase (HPPD) following a single dose to healthy male volunteers

AIMS

NTBC (2-(2-nitro-4-fluoromethylbenzoyl)-1,3-cyclohexanedione) and mesotrione (2-(4-methylsulphonyl-2-nitrobenzoyl)-1,3-cyclohexanedione) are inhibitors of 4-hydroxyphenyl pyruvate dioxygenase (HPPD). NTBC has been successfully used as a treatment for hereditary tyrosinaemia type 1 (HT-1), while mesotrione has been developed as an herbicide. The pharmacokinetics of the two compounds were investigated in healthy male volunteers following single oral administration. The aim of the NTBC study was to assess the bioequivalence of two different formulations and to determine the extent of the induced tyrosinaemia. The mesotrione study was performed to determine the magnitude and duration of the effect on tyrosine catabolism. Additionally, the urinary excretion of unchanged mesotrione was measured to assess the importance of this route of clearance and to help develop a strategy for monitoring occupational exposure.

METHODS

A total of 28 volunteers participated in two separate studies with the compounds. In the first study, the relative bioavailability of NTBC from liquid and capsule formulations was compared and the effect on plasma tyrosine concentrations measured. In the second study the pharmacokinetics of mesotrione were determined at three doses. Plasma tyrosine concentrations were monitored and the urinary excretion of mesotrione and tyrosine metabolites was measured.

RESULTS

Both compounds were well tolerated at the dose levels studied. Peak plasma concentrations of NTBC were rapidly attained following a single oral dose of 1 mg x kg(-1) body weight of either formulation and the half-life in plasma was approximately 54 h. There were no statistical differences in mean (+/- s.d.) AUC(0,infinity) (capsule 602 +/- 154 vs solution 602 +/- 146 microg x ml(-1) h) or t1/2 (capsule 55 +/- 13 vs solution 54 +/- 8 h) and these parameters supported the bioequivalence of the two formulations. Mesotrione was also rapidly absorbed, with a significant proportion of the dose eliminated unchanged in urine. The plasma half-life was approximately 1 h and was independent of dose and AUC(0,infinity) and Cmax increased linearly with dose. Following administration of 1 mg NTBC x kg(-1) in either formulation, the concentrations of tyrosine in plasma increased to approximately 1100 nmol x ml(-1). Concentrations were still approximately 8 times those of background at 14 days after dosing, but had returned to background levels within 2 months of the second dose. Administration of mesotrione resulted in an increase in tyrosine concentrations which reached a maximum of approximately 300 nmol x ml(-1) following a dose of 4 mg x kg(-1) body weight. Concentrations returned to those of background within 2 days of dosing. Urinary excretion of tyrosine metabolites was increased during the 24 h immediately following a dose of 4 mg mesotrione x kg(-1), but returned to background levels during the following 24 h period.

CONCLUSIONS

NTBC and mesotrione are both inhibitors of HPPD, although the magnitude and duration of their effect on tyrosine concentrations are very different. When normalized for dose, the extent of the induced tyrosinaemia after administration of NTBC and over the duration of these studies, was approximately 400 fold greater than that following administration of mesotrione. The persistent and significant effect on HPPD following administration of NTBC make it suitable for the treatment of patients with hereditary tyrosinaemia type 1 (HT-1), whilst the minimal and transient effects of mesotrione minimize the likelihood of a clinical effect in the event of systemic exposure occurring during occupational use.

Heart weight in infants--a comparison between sudden infant death syndrome and other causes of death

Heart and body weights were compared with regard to heart pathology and cause of death in well-defined groups of infants under 1 y of age. In the period 1980 to 1998, out of 468 infants autopsied at the Department of Forensic Medicine in Stockholm, Sweden, 331 died of sudden infant death syndrome (SIDS), while 137 died of other causes. Physical violence was the known cause of death in 30 infants and cardiovascular malformations in another 19. Inflammatory alterations of the myocardium were found in 74 cases (16%): in 17 cases (3.6%) myocarditis was interpreted as the main cause of death; in 45 (10%) it was interpreted as contributing to SIDS and in 12 cases (2.5%) it was observed but judged not to be a contributory cause of death in non-SIDS victims. Two of these infants died as a result of physical violence. Body weight was the best predictor for heart weight as analysed by multiple regression, including age, sex, body weight, length, BMI and birth weight. An equation for estimating heart weight from body weight gave an accuracy within the range 0.75-1.25 in 89.2% and 85.0% of the SIDS and non-SIDS groups, respectively.

CONCLUSION

Body weight is the best predictor for estimating heart weight. No evidence supported the notion that heart weight, body weight or birth weight of SIDS victims differs from non-SIDS, although heart weight in infants with cardiovascular malformations deviated from observations in the other groups.

Stage-specific inhibition of deoxyribonucleic acid synthesis and induction of apoptosis by antracyclines in cultured rat spermatogenic cells

A rapid in vitro method has been developed to detect early effects of cytostatic drugs on rat spermatogenesis. The induction of programmed cell death (apoptosis) and changes in DNA synthesis induced by doxorubicin and idarubicin were measured in specific stages of the cycle of seminiferous epithelium including mitotic (stage V) and meiotic (stage VIII-IX) S-phase cells. The model was used to investigate the protective effect of an organic thiophosphate, amifostine, against the toxicity of antracyclines. Premitotic DNA synthesis was found to be more sensitive than premeiotic DNA synthesis to antracyclines. Idarubicin was more toxic than doxorubicin to germ cells in inducing apoptosis and suppressing DNA synthesis. Amifostine had no protective effect against doxorubicin- or idarubicin-induced inhibition of DNA synthesis. In contrast, a significant stimulation of DNA synthesis in premitotic cells by amifostine was found, suggesting that this compound may have a stimulative effect on spermatogenic stem cells. These data show that stage-specific dissection of the seminiferous tubules and their in vitro exposure to predetermined doses of drugs may give us a unique possibility to detect drug action and protection against the cytotoxicity of antineoplastic agents at the cellular level of the spermatogenic cycle.

Age-dependent variations in white adipose tissue glycerol and lactate production after surgery measured by microdialysis in neonates and children

In previous studies, we observed that lactate concentrations in interstitial white adipose tissue are higher in small infants than in adults. Moreover, no lipolysis following catecholamine challenge has been reported in neonates and small infants. Our aim was to determine with microdialysis whether the above mentioned age-dependent changes could be detected in situ after surgery. A microdialysis catheter was introduced into the abdominal subcutaneous tissue in 13 neonates and 12 children undergoing surgery. Interstitial concentrations of glucose, lactate and glycerol were measured hourly during the first 20 postoperative hours. The concentrations of lactate in interstitial white adipose tissue were consistently higher in neonates compared to older children, with a significant difference during the 9-18 h postoperative period (P < 0.05). A significant difference in the lactate:glucose ratio was observed at 1-2, 8-10, 15 and 18 h postoperatively (P < 0.05). No significant differences were observed between the two groups with respect to glycerol and glucose concentrations. Interstitial lactate concentrations in white adipose tissue were higher in neonates compared with children in the early postoperative period. No age-dependent difference in postoperative lipolysis, measured as interstitial glycerol concentrations, was observed. Thus, an age-dependent difference in interstitial lactate production, but not lipolysis, was detected in the early postoperative period.

Plasma pharmacokinetics of etoposide (VP-16) after i.v. administration to children

The pharmacokinetics of etoposide (VP-16), a semi-synthetic derivative of podophyllotoxin, were studied in 16 pediatric patients (median age 8.3 years; range 4 months to 22 years) including two girls with Down's syndrome (DS). The drug was administered as infusions (1-3 h) in a wide range of doses (9-322 mg, corresponding to 32-210 mg/m2). The area under the plasma concentration versus time curve (AUC), dose normalized by the body surface area, was independent of age, while AUC normalized by the dose in mg/kg increased with increasing age of the patients. The interpatient variability of AUC, normalized for the dose in mg/m2, was 23% (CV) compared to 32% (CV) normalized for the dose in mg/kg. The terminal half-life time was 4.1 h (median value; range 2.0-7.8 h). The pharmacokinetics of etoposide in children with DS and chromosomally normal children were very similar with regard to systemic drug exposure and plasma half-life time. From the pharmacokinetic point of view it was therefore not necessary to make any dose modifications in the two girls with DS. The two DS patients did not experience any enhanced degree of toxicity from their etoposide treatments. The results support that dosing of etoposide to children should be based on body surface area.

A comparative pharmacokinetic study of doxorubicin and 4'-epi-doxorubicin in children with acute lymphocytic leukemia using a limited sampling procedure

Antraquinone glycosides are an important class of antineoplastic drugs, frequently used for treatment of a variety of malignancies in children. Doxorubicin (Dox) is the most frequently used drug within this class of antineoplastics. 4'-epi-doxorubicin (Epi), a Dox isomer, was developed with the aim of reducing risks for fatal heart toxicity observed with Dox. The aim of the present study was to investigate the pharmacokinetics of Dox and Epi in children with acute lymphocytic leukemia. In total 31 patients (13 females and 18 males; median age 5.4 years; range 0.73-15.3 years) were studied using a simplified sampling procedure. The pharmacokinetic differences of the two drugs were established by their simultaneous administration. The plasma pharmacokinetics of neither Dox nor Epi correlated with the age of the patients. There were no gender differences in dose-normalized maximum concentrations of neither Dox nor of Epi. The inter-patient variation of the dose-normalized maximum concentrations of Dox and Epi is larger among females than among males. The Cmax ratio Dox/Epi was 1.39+/-0.19 (mean +/- SD). The pharmacokinetic differences of Dox and Epi in children, although less pronounced than in adults, are still of a magnitude that might be of clinical importance.

Cisplatin-induced hearing loss: influence of the mode of drug administration in the guinea pig

Cisplatin (8 mg/kg) was given intravenously to guinea pigs either as a 15 s bolus injection (25 animals) or as a 1 h infusion (28 animals). To determine the influence of the mode of cisplatin administration and pharmacokinetics on the ototoxic side-effect, the concentrations of cisplatin and the biotransformation product monoaquated cisplatin were determined in blood ultrafiltrate using liquid chromatography with post-column derivatization. Ototoxic effect was evaluated as difference in pre- and 96 h post-exposure auditory brainstem response (ABR) threshold. The cisplatin peak concentration was considerably higher, 19.2+/-2.4 microg/ml, in the bolus injection group than in the infusion group, 6.7+/-0.5 microg/ml (mean+/-S.E.M.). The area under the blood ultrafiltrate concentration time curve (AUC) for cisplatin was slightly greater in the infusion group, 442+/-26 microg/ml/min, than in the bolus injection group, 340+/-5 microg/ml/min. For monoaqua cisplatin, the AUC was not different between the groups (bolus injection: 30.8+/-1. 5 microg/ml/min, infusion: 34.1+/-3.3 microg/ml/min). A significant ototoxic effect was observed in both groups at 20 and 12.5 kHz, but there was no difference between the groups in the extent of threshold shift. The interindividual variability in susceptibility to ABR threshold shift was far greater than the variability in pharmacokinetics, suggesting that other factors are more important in determining the degree of hearing loss.

Bioavailability of aciclovir after oral administration of aciclovir and its prodrug valaciclovir to patients with leukopenia after chemotherapy

The median bioavailabilities of aciclovir after administration of aciclovir and its prodrug valaciclovir were 21.5 and 70.1%, respectively, in 12 patients with malignant hematological diseases with leukopenia after chemotherapy. The interindividual variations of the bioavailability were 48.5 and 21.0% after administration of aciclovir and valaciclovir, respectively. Neither the bioavailability nor the interindividual variation of area under the concentration-time curve of oral aciclovir or valaciclovir differed from that reported in healthy volunteers.

In vitro cellular accumulation and cytotoxicity of liposomal and conventional formulations of daunorubicin and doxorubicin in resistant K562 cells

Previous investigations have indicated the possibility to circumvent multidrug resistance (MDR) by incorporation of an anthracycline into liposomes. We examined the in vitro cytotoxicity and cellular drug accumulation of the anthracyclines daunorubicin and doxorubicin compared with the commercially available liposomal formulations DaunoXome and Caelyx in human myelogenous leukemia K562 cells. The drug-sensitive parental K562/K line was compared with the P-glykoprotein (P-gp)-expressing cell lines K562/Dnr and K562/Vcr. Two cell lines with reduced levels of topoisomerase II (K562/Nov and K562/Ida) were also included. The cytotoxicity was determined by fluorometric microculture cytotoxicity assay and the cellular drug levels were determined by high performance liquid chromatograghy. There was a strong inverse correlation between P-gp levels and cellular drug accumulation (rho = -0.83, p = 0.04) and cytotoxicity (rho = -0.95, p = 0.01) of daunorubicin. Also the cytotoxicity of DaunoXome and doxorubicin was related to P-gp levels (rho = -0.96, p = 0.01 and rho = -0.90, p = 0.07, respectively). Caelyx did not show any cytotoxic effect due to impaired cellular uptake of the pegylated liposome. Regardless of the P-gp levels of the treated cells, DaunoXome showed the same cytotoxic effect despite lower intracellular accumulation (range 22-47%), compared with conventional daunorubicin.

A randomized trial on effects of hormone therapy on ambulatory blood pressure and lipoprotein levels in women with coronary artery disease

OBJECTIVE

To investigate 1-year effects of hormone replacement therapy (HRT) on ambulatory blood pressure (ABP) and lipoprotein levels in postmenopausal women with coronary artery disease (CAD).

METHODS

Sixty patients at a mean age (+/- SD) of 59 +/- 7 years were randomized into three groups: conjugated equine oestrogens (CEE) 0.625 mg daily (n = 20), 50 microg 17beta-oestradiol transdermally (TTSE) per 24 h (n = 20) or placebo (n = 20) for 18 days, then combined with medroxyprogesterone acetate 5 mg for 10 days. Each cycle of 28 days was repeated for one year.

RESULTS

Night-time systolic ABP had decreased by 9.6% (P= 0.0075) in 15 of 18 women in the CEE group and by 22% in 12 of 13 women (P = 0.0034) in the placebo group after 1 year. In the CEE group, a 4.6% rise in daytime systolic ABP (P< 0.05) and a 4.2% rise in night-time systolic ABP (P< 0.05) appeared from baseline to 6 months in 13 of 18 women. In the CEE group (14 women analysed), high-density lipoprotein levels showed a 15.8% increase (P= 0.0018) in 13 women, low-density lipoprotein levels a 15.2% decrease (P= 0.0129) in 12 women and total cholesterol levels a 7.5% decrease (P = 0.057) in 11 women after 1 year. Triglyceride levels showed no changes. In the TTSE group and in the placebo group, with 12 and 13 women analysed respectively, no significant changes appeared.

CONCLUSIONS

One year of HRT in patients with CAD does not influence ABP. Oral HRT induces beneficial effects on lipoprotein levels.

In vivo evaluation of the biodistribution of 11C-labeled PD153035 in rats without and with neuroblastoma implants

The biodistribution of 11C-labeled 4-(3-bromoanilino)-6,7-dimethoxyquinazoline, an inhibitor of the epidermal growth factor (EGF) receptor tyrosine kinase, has been evaluated in vivo in rats using positron emission tomography (PET). Time-activity data obtained after i.v. administration in one rat revealed that the radiotracer rapidly cleared from plasma with subsequent uptake in major organs of the body (brain, heart, liver, gastrointestinal tract and bladder). Uptake in proliferating tissue in rats with human neuroblastoma xenografts indicate that [O-11C-methyl]PD153035 shows promise as a new agent for in vivo imaging of tumors with PET.

Anthraquinone-induced cell injury: acute toxicity of carminomycin, epirubicin, idarubicin and mitoxantrone in isolated cardiomyocytes

Acute toxic effects of the antineoplastic anthraquinones carminomycin, epirubicin, idarubicin and mitoxantrone were studied in primary cultures of cardiomyocytes, which were isolated from adult rats. Both time- and concentration-dependent changes of cell structure and viability (trypan blue exclusion) following incubation of myocytes with subclinical, clinical and toxic concentrations of the anthraquinones were examined by light microscopy. The area under the decay curve of viable and rod-shaped myocytes was used to express cytotoxicity of the drugs. Mitoxantrone was found to reduce cell viability and number of rod-shaped cells to the greatest extent, followed by carminomycin, idarubicin and epirubicin. A significantly lower accumulation in cardiomyocytes was obtained with epirubicin and idarubicin compared with carminomycin. An inhibitory effect on oxygen consumption by the cells occurred already at 0.1 microM with epirubicin, whereas inhibition caused by other anthraquinones was less pronounced. Our data indicate a weak association of net accumulation and the toxicity parameter IC50 for carminomycin and idarubicin. In contrast to these results, a more significant correlation of cytotoxicity and anthraquinone lipophilicity was found, which suggests that the lipophilic character of a particular anthraquinone may be an important factor in drug-induced acute cardiotoxicity.

Neuropeptide Y response to tracheal intubation in anaesthetized children: effects of clonidine vs midazolam as premedication

We have determined if tracheal intubation causes an increase in neuropeptide Y (NPY), a marker of major adrenergic activation, and investigated if rectal premedication with clonidine 2.5 micrograms kg-1 might be capable of attenuating the stress response to tracheal intubation compared with midazolam 300 micrograms kg-1, in 20 paediatric patients (1-9 yr). Prospective randomization was performed in a double-blind manner. After induction of anaesthesia with 1% isoflurane, tracheal intubation was performed, and norepinephrine, NPY concentrations and haemodynamic variables were recorded. Tracheal intubation did not increase NPY plasma concentrations, despite transient increases in norepinephrine concentrations, heart rate and arterial pressure. There was no significant difference between the two groups. We conclude that the adrenergic stress reaction in response to tracheal intubation in children was short-lived and of limited magnitude, as indicated by the lack of NPY release.

Stability of 5-aminolevulinic acid in aqueous solution

The chemical stability of 5-aminolevulinic acid (ALA) was studied in aqueous solution as a function of concentration, pH, temperature and in the presence of ethylenediaminetetraacetic acid (EDTA). The degradation of ALA was followed by reversed-phase liquid chromatography using a pH where ALA is protonated (pKa1=3.90; pKa2=8. 05, as determined potentiometrically). ALA was degraded by a reaction following second order kinetics. Stock solutions of 1% (60 mM) ALA were incubated at 50 degrees C. At pH 2.35, ALA was stable during the whole incubation period (37 days). The half-lives for the second-order decomposition of 1% ALA at pH 4.81 and 7.42 were 257 and 3.0 h, respectively. The degradation rate increased about 1.5 times with each 10 degrees C rise in temperature at pH 7.53 within the range studied (37-85 degrees C). The energy of activation, Ea, for the second-order decomposition of ALA was 43.7 kJmol-1. EDTA did not influence the degradation of ALA when a mixture of 1% ALA and 1% EDTA was incubated at pH 7.42.

Pharmacokinetics and effects of intravesical oxybutynin on the paediatric neurogenic bladder

OBJECTIVE

To evaluate the pharmacokinetics of both oxybutynin and its active metabolite, N-desethyl oxybutynin (NDO), when the drug is instilled directly into the bladder in children with myelodysplasia and neurogenic bladder disturbance, in whom it may improve continence and decrease the risk of upper urinary tract deterioration.

PATIENTS AND METHODS

The study comprised 13 children (five girls and eight boys, mean age 9.3 years, range 1-15) with neurogenic bladders who were treated using clean intermittent catheterization and intravesical instillation of a sterile, pharmacy-produced solution of oxybutynin. Steady-state minimum plasma levels of oxybutynin and NDO, together with their effect on urodynamic variables and incontinence, were evaluated. The dose (0.04-0.17 mg/kg, mean 0.1 mg/kg) was instilled twice daily.

RESULTS

The effects of the drug on incontinence and urodynamic variables were pronounced, improving both in most cases. Minimum plasma levels were < 0.3-7.2 ng/mL for oxybutynin and 0.8-14 ng/mL for NDO. The ratio of oxybutynin to NDO was 0.29-0.83 (mean 0.47).

CONCLUSION

There was no clear relationship between minimum plasma levels of the drug or NDO and their clinical effects; however, the combination of oxybutynin and NDO seemed to be more strongly correlated with the clinical effects.

Follow-up of long-time treatment with intravesical oxybutynin for neurogenic bladder in children

OBJECTIVE

Anticholinergic treatment for the hyperreflexic neurogenic bladder in childhood is an established method, together with clean intermittent catheterization (CIC), to promote continence and protect the upper urinary tract from deterioration. Recently, the use of oxybutynin, a compound with anticholinergic, smooth muscle relaxant and local anesthetic effects, has become widely used with both oral and intravesical administration.

METHOD

In this study we report 39 children with myelodysplasia, neurogenic bladder disturbance with detrusor hyperreflexia and/or high bladder pressure treated with CIC to which intravesical oxybutynin 0.1 mg/kg twice daily was added and administered as a sterile pharmacy-produced solution. The follow-up period was 0.66-5 years (mean 2.25).

RESULTS

Continence was clearly promoted and urodynamic parameters improved whereas an increased occurrence of asymptomatic bacteriuria and lower urinary tract infections was noted. Compliance was good, adverse reactions rare, and in some cases vesicoureteral reflux (VUR) resolved. Also infants and very young children were treated without complications.

CONCLUSIONS

Intravesical oxybutynin is effective to diminish bladder pathophysiology and promote continence in this patient group and is also well tolerated. Attention should be paid to the occurrence of urinary tract infections and VUR may resolve.

Does sublingual 17 beta-oestradiol have any effects on exercise capacity and myocardial ischaemia in post-menopausal women with stable coronary artery disease?

BACKGROUND

A variety of vascular effects have been ascribed to 17 beta-oestradiol. These effects may partially explain the reduced incidence of cardiovascular disease found in post-menopausal women on oestrogen replacement therapy.

OBJECTIVES

To evaluate the effects of 2 mg sublingual 17 beta-oestradiol on exercise capacity, exercise-induced myocardial ischaemia and circulating levels of endothelin-1 in post-menopausal women with stable coronary artery disease.

METHODS

Twelve post-menopausal women, mean age 61 (range 52-72) years, with angiographically verified significant coronary artery disease, were randomly assigned to 2 mg of sublingual 17 beta-oestradiol, 2.5 mg of buccal nitroglycerine and to placebo in a double-blind cross-over study design with at least 2 days between each of the study arms. Antianginal medications, with the exception of beta-blockers, were discontinued before investigation. All study patients underwent a maximal bicycle exercise test 30 min after drug intake. Blood was withdrawn immediately before and up to 8 h after medication for analyses of circulating levels of oestradiol and endothelin-1.

RESULTS

The mean serum levels of oestradiol increased from a control level of 72 +/- 28 pmol.l-1 to 3557 +/- 1731 pmol.l-1 after 30 min and to 5028 +/- 3971 pmol.l-1 after 60 min with a gradual decline thereafter. Sublingual 17 beta-oestradiol did not induce any improvement in exercise duration when compared with nitroglycerin and placebo (500 +/- 112 s, 505 +/- 107 s, 498 +/- 157 s), and did not influence time to onset of ST-segment depression (358 +/- 89 s, 436 +/- 93 s, 384 +/- 116 s). The plasma levels of endothelin-1 did not change after administration of 17 beta-oestradiol, nitroglycerin or placebo.

CONCLUSIONS

No effects of exercise capacity, exercise-induced acute ischaemia, or plasma levels of endothelin-1 were found after a single dose of 2 mg 17 beta-oestradiol in post-menopausal women with documented coronary artery disease.

Plasma levels of clonidine following epidural bolus injection in children

BACKGROUND

The use of clonidine as an adjunct to epidural administration of local anesthetics in children has been reported to substantially improve the duration and quality of postoperative analgesia. The aims of the present study were to determine the pharmacokinetic profile and to investigate the interaction between postoperative sedation and analgesia after epidurally administered clonidine in children.

METHODS

Plasma levels of clonidine (0-10 h postop) and assessment of postoperative analgesia and sedation (0-24 h postop) were performed at predetermined intervals following lumbar epidural administration of bupivacaine 2.0 mg/kg and clonidine 2 mg/kg in 8 children undergoing ureteral re-implantation surgery using general anesthesia (age range: 1-9 yr, weight range: 9-41 kg). Plasma levels of clonidine were analyzed by radioimmunoassay, and sedation and analgesia were assessed by previously described scoring systems.

RESULTS

The venous plasma pharmacokinetics of clonidine following epidural administration showed a considerable interindividual variation. Cmax and Tmax values of clonidine were found to be within the 0.45-0.77 ng/mL and 48-193 min range, respectively. The time to absorb 95% of the clonidine dose from the epidural space into plasma varied between 36 min and 7.6 h. In 6 of the 8 patients postoperative analgesia substantially outlasted the duration of sedation (> or = 2 h). Sedation could not be detected in any patients at plasma concentrations below 0.3 ng/mL.

CONCLUSIONS

The pharmacokinetic profile associated with epidural clonidine administration in children (1-9 y) was similar to that previously reported in adults. The postoperative analgesia seen after administration of epidural bupivacaine-clonidine during general anesthesia in children cannot only be explained by residual postoperative sedation.