Induction of aromatic-L-amino acid decarboxylase by decarboxylase inhibitors in idiopathic parkinsonism

We evaluated the effect of administration of L-dopa, alone or in combination with a peripheral decarboxylase inhibitor, on plasma levels of aromatic-L-amino acid decarboxylase (ALAAD). After single-dose administration of L-dopa plus benserazide (Madopar) in healthy subjects and in chronically treated patients with parkinsonism, plasma ALAAD followed for 2 to 3 hours fell, but returned to predosing levels within 90 minutes. Four groups of patients with idiopathic parkinsonism were studied during chronic treatment: Group I, no L-dopa treatment (n = 31); Group II, L-dopa alone (n = 15); Group III, L-dopa plus benserazide (n = 28); and Group IV, L-dopa plus carbidopa (Sinemet, n = 30). Plasma ALAAD 2 hours after dosing was normal in Groups I and II. ALAAD was increased threefold in Groups III and IV, suggesting induction of ALAAD by the coadministration of a peripheral decarboxylase inhibitor. In a study of 3 patients in whom L-dopa/benserazide was started, plasma ALAAD rose gradually over 3 to 4 weeks. Further detailed pharmacokinetic studies of L-dopa, dopamine, and ALAAD in plasma and cerebrospinal fluid are required to determine if the apparent ALAAD induction by a peripheral decarboxylase inhibitor may be related to the loss of clinical efficacy of combination therapy in some patients and how it is related to end-of-dose deterioration and on-off phenomena.

[Pharmacokinetic, bacteriological and clinical studies on imipenem/cilastatin sodium in neonates]

Pharmacokinetic, bacteriological and clinical studies on imipenem/cilastatin sodium (IPM/CS) were performed in neonates. The results were as follow: 1. A total of 27 patients consisting of 17 mature and 10 immature infants were treated with IPM/CS. Each dose was 20 mg/20 mg/kg, and it was administered 2 approximately 3 times daily, in a 1-hour intravenous drip infusion for 3 approximately 12 days. The clinical efficacy of IPM/CS in 10 patients with bacterial infections (2 with sepsis, 3 with suspected sepsis, 2 with pneumonia, 2 with urinary tract infection and 1 with acute omphalitis) was evaluated as excellent in all patients, with an efficacy rate of 100%. All 5 causative organisms found in 5 patients (Staphylococcus aureus in 1, Staphylococcus epidermidis in 1, Escherichia coli in 2 and Flavobacterium meningosepticum in 1) were eradicated. Among 27 patients administered IPM/CS, adverse reactions were observed in 2 patients. These were rash and diarrhea. As for abnormal laboratory test values, elevations of GOT and GPT were observed. 2. MICs of IPM against 14 clinical isolates (S. epidermidis 1, S. aureus 6, Streptococcus agalactiae 4, E. coli 1, Enterobacter cloacae 1 and F. meningosepticum 1) from neonatal patients with bacterial infections were examined. IPM showed good antibacterial activity comparable to that of cefotaxime against S. agalactiae; however, the activity against methicillin-resistant S. aureus was poor. 3. Serum levels of IPM and CS were investigated in a total of 22 patients consisting of 15 mature and 7 immature infants after 20 mg/20 mg/kg of IPM/CS was administered. IPM and CS produced peak serum levels at the end of the drip infusion. In mature infants, peak serum levels of IPM and CS were 31.8 micrograms/ml (17.1 approximately 59.0 micrograms/ml) and 59.9 micrograms/ml (35.6 approximately 99.0 micrograms/ml), respectively. In low birth weight infants, these were 25.0 micrograms/ml (16.8 approximately 41.8 micrograms/ml) and 55.2 micrograms/ml (33.8 approximately 82.4 micrograms/ml), respectively. Half-lives of IPM and CS were 1.0 approximately 2.7 hrs. and 0.9 approximately 7.4 hrs. in mature infants, and 1.6 approximately 3.0 hrs. and 1.3 approximately 9.7 hrs. in immature infants, respectively. Generally the longer half-lives were observed in the younger neonates. Serum levels of CS remained higher and half-lives of CS were longer than those of IPM. The pharmacokinetics in neonates were different from those in adults or children.(ABSTRACT TRUNCATED AT 400 WORDS)

Treatment of idiopathic parkinsonism with L-dopa in the absence and presence of decarboxylase inhibitors: effects on plasma levels of L-dopa, dopa decarboxylase, catecholamines and 3-O-methyl-dopa

The effect of levodopa (L-dopa), alone or in combination with a peripheral decarboxylase inhibitor (PDI), on plasma levels of aromatic-L-amino acid decarboxylase (ALAAD, = dopa decarboxylase), L-dopa, 3-O-methyl-dopa (3-OMD), dopamine (DA), noradrenaline, adrenaline and dopamine beta-hydroxylase has been studied. In healthy subjects and in patients with parkinsonism plasma ALAAD level fell after administration of L-dopa + benserazide, but returned to previous levels within 90 min. In a cross-sectional study blood was obtained, 2 h after dosing, from 104 patients with idiopathic parkinsonism, divided into four groups: no L-dopa treatment (group 1), L-dopa alone (group 2), L-dopa + benserazide (Madopar) (group 3) and L-dopa + carbidopa (Sinemet) (group 4). Plasma ALAAD, which was normal in groups 1 and 2, was increased 3-fold in groups 3 and 4, indicating that there was induction of ALAAD by the co-administration of PDI. Despite this induction of ALAAD, in groups 3 and 4, with half the daily L-dopa dose compared with group 2, plasma L-dopa and 3-OMD levels were 5 times higher, while plasma DA levels were not different. The DA/L-dopa ratio was decreased 5-fold in group 2 and 16-fold in groups 3 and 4 as compared with group 1. Neither 3-OMD levels nor 3-OMD/L-dopa ratios correlated with the occurrence of on-off fluctuations. In a longitudinal study of three patients started on Madopar treatment the induction of plasma ALAAD was found to occur gradually over 3-4 weeks. Further detailed pharmacokinetic studies in plasma and cerebrospinal fluid are required in order to elucidate whether the ALAAD induction by PDI may be related to the loss of clinical efficacy of combination therapy in some patients and how it is related to end-of-dose deterioration and on-off phenomena.

[Pharmacokinetic, bacteriological and clinical studies on imipenem/cilastatin sodium in neonates]

Pharmacokinetic, bacteriological and clinical studies on imipenem/cilastatin sodium (IPM/CS) were performed in neonates. The results obtained are summarized as follows. 1. Plasma levels and urinary excretion of IPM and CS sodium were determined in 7 neonates with ages between 7 and 26 days (gestation periods were 37 to 41 weeks and birth weights were 2,410 to 3,890 g) upon 1 hour drip intravenous infusion of IPM/CS at 10 mg/10 mg/kg, or 20 mg/20 mg/kg. Mean plasma concentrations of IPM reached their peaks at the end of infusion with levels of 12.7 +/- 3.0 micrograms/ml for the group given 10 mg/10 mg/kg, and 19.1 +/- 4.1 micrograms/ml for 20 mg/20 mg/kg. The concentration of IPM in plasma showed a dose-response to the 10 mg/10 mg/kg and 20 mg/20 mg/kg dosages. Concentrations decreased with half-lives of 1.87 +/- 0.71 hours and 1.97 +/- 0.21 hours for the low and the high dosages, and plasma levels at 8 hours after administration were 0.3 +/- 0.1 microgram/ml and 0.8 +/- 0.3 microgram/ml, respectively. Mean urinary recovery rates in 8 hours after administration were 37.6 +/- 11.8% and 26.8 +/- 17.2% for the low and the high dosages. While, mean plasma concentrations and mean urinary recovery rates of CS were higher than those of IPM, mean plasma half-lives of CS were similar to IPM. 2. IPM/CS was administered to 11 neonatal patients (with ages between 1 and 26 days) of various bacterial infections, and clinical effectiveness, bacteriological efficacy and adverse reactions were evaluated. Clinical efficacies in cases including 7 with acute pneumonia and 1 each with suspected septicemia, intrauterine infection, acute urinary tract infection and periproctal abscess were judged excellent in 10 and good in 1 case, and the efficacy rate was 100%. Causative organisms isolated from these patients included 3 strains of Escherichia coli and 1 strain each of Streptococcus pyogenes, Streptococcus agalactiae Enterococcus faecalis and Haemophilus influenzae. All the organisms were eradicated by IPM/CS, thus the bacteriological eradication rate was 100%. No adverse reactions were observed, but decreased platelet in 1 patient and increased GOT in 2 patients were found as abnormal laboratory test values. These changes, however were transient, and returned to normal after discontinuation of IPM/CS. It was concluded that the clinical results of IPM/CS are indicative of excellent efficacy, safety and usefulness of the drug in the treatment of infections in neonates.

Co-trimoxazole (sulphamethoxazole plus trimethoprim) peritoneal barrier transfer pharmacokinetics

The pharmacokinetics of co-trimoxazole (sulphamethoxazole plus trimethoprim) were studied in end-stage renal disease in patients undergoing treatment with continuous ambulatory peritoneal dialysis (CAPD) and free of peritonitis. Plasma and dialysate concentrations were monitored for 1 exchange after administration of a single oral or intraperitoneal dose of co-trimoxazole, and were fitted by a pharmacokinetic model that took into account the equilibrium nature of CAPD by including return from the peritoneum in oral studies and from the plasma in intraperitoneal studies. Clearances were calculated and compared by analysis of variance. There was a significant effect of direction of flow (p less than 0.01), plasma-peritoneal clearances being larger than peritoneal-plasma clearances for both drugs. In addition, there was a significant difference (p less than 0.0001) between sulphamethoxazole clearances and trimethoprim clearances, with the latter being greater in both directions.

[Pharmacokinetic and clinical evaluations of imipenem/cilastatin sodium in neonates and premature infants]

Pharmacokinetic and clinical studies on imipenem/cilastatin sodium (IPM/CS), a beta-lactam antibiotic of the carbapenem class and its renal dehydropeptidase-I inhibitor in a 1:1 ratio, were performed in neonates, premature infants and an infant. IPM/CS was administered intravenously to 4 neonates and 5 premature infants at a dose level of 10 mg/kg. Plasma levels and urinary excretion of IPM and CS were determined in 2 neonates and 2 premature infants after 30-minute infusion, and in 2 neonates and 3 premature infants after 1-hour infusion. Plasma and cerebrospinal fluid (CSF) concentrations of IPM and CS were determined in 2 cases with purulent meningitis with ages of 2 and 26 days and 1 with purulent meningitis/bacteremia with an age of 4 days. The drug was administered to a total of 31 patients with ages between 0 and 30 days, consisting of neonates, premature infants and an infant (24 suffering with various bacterial infections, 5 treated for prophylaxis of infections and 2 treated for aseptic meningitis diagnosed at the completion of therapy) by intravenous drip infusion in a mean daily dose level of 50.1 mg/kg in 2 to 4 divided doses for 9 days on the average. Clinical efficacy, prophylactic effectiveness and bacteriological response of IPM/CS were evaluated in 29 cases. Adverse effects and abnormal laboratory test results were examined in 31 cases including 2 drop-out cases. The results obtained are summarized as follows. 1. Plasma concentrations of IPM and CS after 30-minute infusion of the drug reached their peaks at the end of administration, and obtained values were 22.4 to 29.0 micrograms/ml for IPM and 26.3 to 34.6 micrograms/ml for CS, thus peak plasma levels of CS were a little higher than IPM. Plasma half-lives of IPM were 1.05 to 2.43 hours, and those of CS were 1.24 to 4.76 hours, and the half-life of CS tended to be longer than that of IPM. Drug concentrations in plasma after 1-hour infusion of IPM/CS reached their peaks at the end of administration and the levels of CS (25.7 to 32.0 micrograms/ml) were a little higher than those of IPM (20.8 to 23.9 micrograms/ml). Plasma half-lives of IPM were 1.40 to 1.63 hours, whereas those of CS were 1.51 to 2.90 hours. The half-life of CS tended to be longer than IPM. 2.(ABSTRACT TRUNCATED AT 400 WORDS)

[Chemico-physical property and bile acid binding capacity of several antacids]

Liquid alginate (Gaviscon) binds small amount of bile acids. At pH 7 its viscosity (at low shear rate) is higher than that of other antiacids. High viscosity reduces the diffusion rate of bile salts and glucose and this property can play a role in the treatment of gastro-esophageal and duodeno-gastric refluxes.

Pharmacokinetics of sulfadiazine/trimethoprim in neonatal male calves: effect of age and penetration into cerebrospinal fluid

Sulfadiazine (SDZ)/trimethoprim (TMP; 30 mg of SDZ/TMP/kg of body weight) was given IV to the same 6 male calves at 1, 7, and 42 days of age and to 2 additional calves at 7 days of age. Serum concentrations of SDZ and TMP were best represented by a 2-compartment open model, but in 42-day-old calves, CSF concentrations of both drugs were best represented by a 1-compartment open model with first-order input. Between 1 and 42 days of age, the elimination half-life (t1/2(beta)) of SDZ decreased from 5.7 to 3.6 hours, and total body clearance (CLtot) increased from 1.43 to 1.88 ml/min/kg; the area under the curve (AUC0----infinity) decreased from 291.5 to 225.4 mg/L.h. The distribution coefficient (Vd(area)/kg of body weight) decreased with age, changing from 0.72 to 0.59 L/kg, between 1 and 42 days of age. Therapeutic concentrations of SDZ in serum (greater than 2 micrograms/ml) were maintained for 24 hours in 1-day-old calves and for about 15 hours in 7- and 42-day-old calves. The elimination rate of TMP increased about 9-fold; t1/2(beta) was 8.4, 2.1, and 0.9 hours, respectively, at 1, 7, and 42 days of age. Other values also reflected an increase in TMP elimination rate with age: CLtot increased from 2.8 to 12 to 28.9 ml/min/kg, k13 increased from 0.336 to 0.654 to 1.664/h and AUC0----infinity decreased from 32.8 to 7.9 to 3.1 mg/L.h, respectively. Therapeutic concentrations (greater than 0.1 microgram/ml) were maintained for 15 hours, 8 hours, and about 6 hours in 1-, 7-, and 42-day-old calves, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue concentrations and bioactivity of amphotericin B in cancer patients treated with amphotericin B-deoxycholate

We have studied amphotericin B concentrations in tissues of 13 cancer patients who died after having received 75 to 1,110 mg (total dose) of amphotericin B-deoxycholate for suspected or proven disseminated fungal infection. Amphotericin B concentrations were measured by high-pressure liquid chromatography (HPLC) and by bioassay, the latter being done on tissue homogenates as well as on tissue methanolic extracts. The fungistatic and fungicidal titers of the tissue homogenates were also tested against three strains of Candida albicans and one strain of Aspergillus fumigatus. Tissue concentrations of amphotericin B measured by HPLC varied with the tested tissues as well as with the total dose of amphotericin B-deoxycholate administered and ranged from 0.4 to 147.1 micrograms/g. A mean of 38.3% (range, 23.0 to 51.3%) of the total dose was recovered by HPLC from all of the tested organs. Bioassay of tissue methanolic extracts reached 58 to 81% of the concentration measured by HPLC, whereas only 15 to 41% was recovered from the homogenates. Overall, 27.5% of the total dose was recovered from the liver, 5.2% was recovered from the spleen, 3.2% was recovered from the lungs, and 1.5% was recovered from the kidneys. The median concentration in bile was 7.3 micrograms/ml, suggesting that biliary excretion could contribute to amphotericin B elimination to an estimated range of 0.8 to 14.6% of the daily dose. Fungicidal titers were seldom measured in tissues, but fungistatic titers were observed and were linearly correlated with amphotericin B concentration measured by HPLC. In conclusion, only a small proportion of the amphotericin B administered as amphotericin B-deoxycholate to patients seems diffusible and bioactive.

Phase I trial of trimetrexate glucuronate on a five-day bolus schedule: clinical pharmacology and pharmacodynamics

Trimetrexate glucuronate (TMTX), a nonclassical folate antagonist, has been evaluated clinically on several schedules. We have studied TMTX administered as an iv bolus for 5 consecutive days every 3 weeks in 35 patients with advanced solid tumors. Drug was given at doses ranging from 7.6 to 18.8 mg/m2. The maximal tolerated dose was 13.1 mg/m2 per day x 5 for patients without prior myelotoxic treatment and 7.6 mg/m2 per day x 5 for previously treated patients. Because of wide individual differences in drug tolerance, dose escalation in 25% increments is recommended for patients not experiencing toxic effects. The dose-limiting toxicity was neutropenia. Rash and mucositis were also significant. TMTX concentrations were measured 1 and 24 hours after each dose, and the data were fit by use of a one-compartment pharmacokinetic model. With this simplified sampling and modeling scheme, the mean total body clearance (+/- SD) of trimetrexate was 31 +/- 20 mL/min per m2 and the volume of distribution was 13 +/- 7 L/m2. Mean plasma concentrations 1 hour after a dose were 1.12, 2.43, 3.33, and 3.25 mumol/L at 7.6, 9.1, 10.9, and 13.1 mg/m2, respectively. The mean TMTX concentration (+/- SD) 24 hours after a dose was 114 +/- 87 nmol/L. The mean area under the concentration-versus-time curve at 13.1 mg/m2 was 2,266 mumol.min/L. The drug concentration 1 hour after the first dose and the area under the concentration-versus-time curve were highly correlated with leukopenia and thrombocytopenia (r = .6 and .65 and P = .0007 and .0001, respectively). The maximal tolerated dose on the daily x 5 schedule was 30% of the dose tolerated on an iv bolus schedule. The choice of drug schedule for clinical trials when murine and human pharmacokinetics differ is discussed. Phase II trials are under way with both the iv bolus and the daily x 5 schedules.

The excretion of ketorolac tromethamine into breast milk after multiple oral dosing

We have studied the transfer of the analgesic ketorolac tromethamine into breast milk in ten women aged between 22 and 35 years. Ketorolac administration was started between 2 and 6 days after delivery. The breast milk was not fed to the infant because of maternal antibiotic use (6 patients) or because of jaundice of the baby. 10 mg of ketorolac was given four times daily for two days. Plasma and milk samples were collected on the two dosing days and on the first day after dosing. The plasma and milk were assayed for ketorolac concentrations by HPLC: the quantification limits were 10 ng.ml-1 and 5 ng.ml-1 respectively. The maternal plasma concentrations were within established ranges for ketorolac. In four patients the concentration of ketorolac in the milk was never above 5 ng.ml-1. At 2 h after dosing on both Days 1 and 2 there were quantifiable concentrations of ketorolac in the milk. The range was 5.2 ng.ml-1 to 7.9 ng.ml-1. The ratio of breast milk: plasma concentrations of ketorolac ranged from 0.015 to 0.037. The maximum potential amount of ketorolac that an infant may be exposed to daily could range from 3.16 mg to 7.9 mg, assuming a consumption of between 400 ml and 1 l of breast milk. On a weight-adjusted basis this is equivalent to between 0.16% and 0.40% of the total daily maternal dose.

Pharmacokinetics of ketorolac and p-hydroxyketorolac following oral and intramuscular administration of ketorolac tromethamine

Ketorolac tromethamine (KT), a potent analgesic with cyclooxygenase inhibitory activity, was administered in an open, randomized, single-dose study of Latin-square design to 12 healthy male volunteers. Doses of 30 mg oral (po) and 30, 60, and 90 mg intramuscular (im) KT were administered in solution. Plasma samples were analyzed for ketorolac (K) and its inactive metabolite, p-hydroxyketorolac (PHK), by reversed-phase high-performance liquid chromatography (HPLC). The 30-mg im dose was found to be similar to the 30-mg po dose with respect to total AUC values for both K and PHK. The amount of PHK circulating in plasma was very low as judged by AUC ratios (PHK/K x 100) of 1.9 and 1.5% for the 30-mg po and im doses, respectively. The rate of absorption of K and formation of PHK, as determined by Cmax and Tmax values, was significantly slower following the im doses. Total AUC and Cmax for K and PHK increased linearly with dose after im administration of 30, 60, and 90 mg of KT. The mean plasma half-life of K was remarkably consistent between po and im administration and was independent of dose, ranging from 5.21 to 5.56 hr. The plasma metabolic profile was similar following both routes of administration and graded im doses.

Clinical and pharmacokinetic evaluation of controlled-release levodopa/carbidopa (CR-4) in parkinsonian patients with severe motor fluctuations: a six month follow-up study

The results of a six month open-label study comparing the efficacy of controlled-release levodopa-carbidopa (Sinemet CR-4 200 mg/50 mg) with standard levodopa/carbidopa (250 mg/25 mg) in 17 patients with idiopathic Parkinson's disease and severe response fluctuations, are reported. Major clinical benefits included; improvement of disability, reduction of the number of 'off' periods (predominantly end-of-dose hypokinesia) and a slight increase in 'on' time. No improvement was observed in two of our patients. Mean levodopa plasma levels were comparable between the two types of formulations during optimal treatment, however systemic bioavailability was significantly higher with CR-4. Delayed onset of antiparkinsonian effect of CR-4, resulting from an increase of Tmax for levodopa, was one of the major complaints and required additional small amounts of standard levodopa in three patients.

A phase I trial of trimetrexate glucuronate (NSC 352122) given every 3 weeks: clinical pharmacology and pharmacodynamics

Trimetrexate glucuronate (TMTX), a non-classic folate antagonist, has been evaluated clinically on several schedules. We studied TMTX given as an i.v. bolus over 5-30 min every 3 weeks in 44 patients with advanced solid tumors; it was given at doses ranging from 20 to 275 mg/m2. The maximal tolerated dose (MTD) on this schedule is 220 mg/m2, which we also recommend as a starting dose for phase II studies in patients without extensive prior therapy. Because of wide individual differences in drug tolerance, dose escalation in 25% increments is recommended for non-toxic patients. The principal dose-limiting toxicity was myelosuppression, although in some patients a flu-like syndrome precluded dose escalation. Significant rash and mucositis also frequently occurred in toxic patients. TMTX plasma concentrations were measured after the first dose and the data were fit by two- or three-compartment mammillary pharmacokinetic models. The TMTX clearance rate was 36.5 +/- 21 ml/min per m2 and did not change with dose; non-linearities with increasing dose were apparent in the steady-state volume of distribution (Vss) and in the terminal disposition half-life (t1/2). The difference between pre-treatment and nadir leucocyte counts was correlated with TMTX dose (r = 0.58; P = 0.0006) and with the area under the concentration vs time curve (AUC) (r = 0.41; P = 0.02). Pre-treatment plasma albumin concentrations correlated weakly with the nadir white blood count (r = -0.36; P = 0.047). Optimal schedules for the administration of TMTX have not been established and phase II trials using both bolus and daily X 5 schedules are under way.

Pharmacodynamic evaluation of ofloxacin and trimethoprim-sulfamethoxazole in vaginal fluid of women treated for acute cystitis

Vaginal colonization with Escherichia coli is an integral step in the development of acute cystitis, and persistent vaginal coliform colonization may also be a predisposing step to recurrent urinary tract infections. For this reason, we evaluated antibiotic concentrations in the vaginal fluid, serum, and urine and the vaginal colonization by E. coli of 56 women receiving either ofloxacin (200 mg orally twice a day) or trimethoprim-sulfamethoxazole (TMP-SMX) (160/800 mg orally twice a day) for the treatment of acute cystitis. Ofloxacin and trimethoprim both penetrated into vaginal fluid to a considerably greater extent than sulfamethoxazole. Among 33 patients given ofloxacin, the concentration of the drug in vaginal fluid during one dosage interval ranged from 1.6 to 21.6 micrograms/ml. In 21 women given TMP-SMX the range of drug concentrations in vaginal fluid was 2.6 to 32.5 micrograms/ml for TMP and 1.0 to 6.2 micrograms/ml for SMX. Treatment with both ofloxacin and TMP-SMX remarkably reduced vaginal colonization by E. coli during and up to 30 days after therapy. For the ofloxacin-treated women, eradication of vaginal E. coli was associated with a high ratio of drug concentration in vaginal fluid to that in serum. We conclude that ofloxacin and TMP both achieve high concentrations in vaginal fluid and are equally successful in eradicating E. coli from the vagina.

New antibiotics: carbapenems, monobactams and quinolones

New beta lactams and the quinolone class of antibiotics represent major improvements in the therapy of moderate to severe infections. These newer antibiotics have an extended spectrum of antimicrobial activity, excellent pharmacokinetic properties and low toxicity. The beta lactams include carbapenems, represented by imipenem-cilastatin, and monobactams, represented by aztreonam. Norfloxacin and ciprofloxacin are potent quinolones.

Serum and synovial fluid steady-state concentrations of trimethoprim and sulfadiazine in horses with experimentally induced infectious arthritis

The tarsocrural joints of 11 horses were inoculated with 1.2 to 2.16 x 10(6) viable Staphylococcus aureus organisms susceptible to a trimethoprim-sulfadiazine (TMP-SDZ) combination with minimal inhibitory concentration (MIC) of 0.25 micrograms of TMP/ml and 4.75 micrograms of SDZ/ml. Antimicrobial treatment consisted of oral administration of a TMP-SDZ combination--30 mg/kg of body weight given once daily (group-1 horses) or 60 mg/kg given as 30 mg/kg every 12 hours (group-2 horses). Paired serum and synovial fluid samples were obtained before intra-articular inoculation with the S aureus, after inoculation with S aureus but before antimicrobial treatment, and after inoculation at various hourly intervals after oral administration of the TMP-SDZ combination. The TMP-SDZ combination was administered daily in the 2 dosages for 21 days. Samples were collected after day 3 of repetitive drug administration so that drug steady-state concentration would have been achieved. Serum and synovial fluid samples were analyzed for TMP and SDZ concentrations. Administration of the TMP-SDZ combination at a dosage of 30 mg/kg once daily was not effective in maintaining TMP or SDZ concentrations above the MIC of TMP-SDZ for the S aureus (0.25 and 4.75 micrograms/ml for TMP and SDZ, respectively) in the infected synovial fluid or in maintaining adequate TMP concentration in the serum. The alternative use of the TMP-SDZ combination at a dosage of 60 mg/kg given as 30 mg/kg every 12 hours was effective in maintaining serum and synovial fluid concentrations of TMP and SDZ that were greater than the MIC for the infective organism.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma concentrations of sulfadoxine in healthy and malaria infected Thai subjects

The disposition of sulfadoxine was studied in the presence of pyrimethamine in 18 healthy Thai subjects who had been suffering from falciparum malaria in the 6 months prior to the study, and in 12 Thai patients with acute malaria. The volunteers were administered an oral dose of 500 mg sulfadoxine + 25 mg pyrimethamine (1 Fansidar tablet). They were classified retrospectively as responders (Group I, n = 8) or nonresponders (Group II, n = 10) according to previous response to treatment with Fansidar. The patients were treated with 3 Fansidar tablets corresponding to 1500 mg sulfadoxine and 75 mg pyrimethamine. Five of them were completely cured. Seven patients showed R I or R II resistance. In all cases blood samples were collected up to 288 h post dose. The resultant plasma was analyzed for active (i.e. unchanged) and total sulfadoxine using a modified Bratton-Marshall method. In the healthy volunteers the plasma concentration time course of total sulfadoxine was similar for responding and nonresponding subjects. However, in nonresponders active sulfadoxine tended to show shorter half-lives (harmonic means were 212 h vs 267 h, respectively). Furthermore, significantly higher amounts of metabolites (mainly N4-acetylsulfadoxine) were present in plasma of nonresponders. In contrast to these findings, in malaria patients, plasma concentrations of active and total sulfadoxine were even higher in nonresponders as compared to the subjects who could be successfully cured. Furthermore, in this case there was no increase of the amount of metabolites in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

[Studies of the pharmacokinetics and bioavailability of a new trimethoprim/sulfamethoxazole preparation in healthy volunteers]

The objective of this study was to determine both the pharmacokinetic parameters and the bioavailability of a newly developed trimethoprim/sulfamethoxazole preparation (cotrimoxazole, Kepinol forte, 160 mg of trimethoprim/800 mg of sulfamethoxazole) in comparison with a reference preparation customary in trade and registered according to the AMG 1976, after single oral administration. For this purpose the test and the reference preparation were examined in a randomized 2-way crossover design (Latin square) in 12 volunteers each. Both dosage forms led to maximum plasma levels of approx. 1250 ng/ml of trimethoprim and about 40 micrograms/ml of sulfamethoxazole 1.5-2 h after application; the plasma half-lives were about 9 h for trimethoprim and around 8.5 h for sulfamethoxazole. The statistical comparison (ANOVA, confidence intervals according to Westlake, Pratt-Wilcoxon test) of the pharmacokinetic parameters found in the study resulted in bioequivalence of the newly developed trimethoprim/sulfamethoxazole preparation and the reference preparation. Furthermore, after the administration of both preparations no marked side effects worth mentioning were observed, suggesting a good and comparable clinical tolerability of the two preparations.

[Intraindividual comparison of the elimination kinetics of Lipofundin S and Intralipid in consecutive lipid tolerance tests]

Two intravenous fat tolerance tests (IVFTT) were performed in 16 healthy volunteers and 8 patients suffering from hypertriglyceridemia (HTG). We compared Lipofundin S (Braun, Melsungen) with Intralipid (Kabi Vitrum, Stockholm), using both 10- and 20% concentrations. Time intervals between the tests were 1 h for the volunteers and 2 h for the patients with HTG, respectively. Fractional elimination rates were obtained from light scattering intensity of serum samples. They were significantly higher for Lipofundin S (9.61%/min for healthy men and 12.48%/min for healthy women) compared to Intralipid (7.09%/min for healthy men and 9.41%/min for healthy women). This difference occurred independently of (1) serum triglyceride concentrations and sex of the volunteers, (2) concentrations of lipid emulsions (10 vs. 20%), and (3) the test sequence (Lipofundin S or Intralipid first). This means that the elimination kinetics during an IVFTT are not influenced by a foregoing test. Similar features of both emulsion types were: (1) Faster elimination in women compared to men, and in healthy volunteers compared to HTG patients; (2) inverse correlation between fractional elimination rates and serum triglyceride concentrations. Fractional elimination rates of Lipofundin S and Intralipid were closely interrelated. Obviously there exists an intra-individually characteristic elimination capacity for exogenous triglycerides.

UTIs and two new antibiotics in the elderly

Of the new antimicrobials available for the treatment of urinary tract infections (UTIs), aztreonam and imipenem/cilastatin represent two structurally unique, but distinct, classes of beta-lactam antibiotics. Aztreonam has a directed spectrum of activity covering gram-negative bacilli usually associated with UTIs. In comparative clinical trials of patients with complicated UTIs, aztreonam is well-tolerated and is as effective as conventional control regimens, including aminoglycosides. On the other hand, the antimicrobial spectrum of imipenem/cilastatin includes not only gram-negative bacilli but also gram-positive cocci and anaerobes. As such, this broad-spectrum antibiotic should be reserved for the treatment of mixed infections.