The role of complement in meconium aspiration syndrome.

The complement system is part of the host defense with a number of biological effects, most of which contribute to the inflammatory reaction by activation of cells like leukocytes and endothelial cells. An intact complement system is required for protection against infection and for maintaining internal inflammatory homeostasis. However, the system is a double-edged sword as improperly or uncontrolled activation is disadvantageous and potentially harmful for the host. Meconium aspiration syndrome (MAS) is associated with a local inflammatory reaction in the lungs, frequently described as a chemical pneumonitis. Cytokines, arachidonic acid metabolites and reactive oxygen species are involved in this reaction. We have recently documented that meconium is a potent activator of complement in vitro and in an experimental piglet model of MAS, the latter presenting with an inflammatory profile closely resembling systemic inflammatory response syndrome. We postulate that complement activation may contribute to the pathogenesis of MAS.

High-performance liquid chromatographic determination of (R)-and (S)-proxyphylline in human plasma.

A reversed-phase high-performance liquid chromatographic assay has been developed for determination of (R)-(--)-and (S)-(+)-proxyphylline in human plasma. The procedure is based on liquid-solid extraction of proxyphylline from plasma followed by derivatization of extracted proxyphylline with (--)-camphanoyl chloride. The ratio between the enantiomers is calculated from the peak areas of the corresponding diastereoisomeric proxyphylline camphanates after injection into the liquid chromatograph. The recovery of proxyphylline from plasma was 88% (coefficient of variation = 4%) and proxyphylline was detectable from a plasma concentration of 0.2 micrograms/ml. Three different plasma extraction procedures for proxyphylline using Extrelut, Bond Elut, and Chem Elut columns have been developed and compared, and the rate of derivatization of the proxyphylline enantiomers with camphanoyl chloride has been studied.

High-performance liquid chromatographic determination of citalopram and four of its metabolites in plasma and urine samples from psychiatric patients.

A high-performance liquid chromatographic method is used for the determination of citalopram [1-(3-dimethylaminopropyl)-1-(4-fluorophenyl)-5-phthalancarbonitrile+ ++] and four of its metabolites (the methylamino, amino, propionic acid and N-oxide derivatives) in plasma and urine. The plasma samples were extracted with diethyl ether at pH 10 and pH 4. Filtered urine samples could be injected directly on to the column. Steady-state drug and metabolite levels were investigated in fifteen psychiatric patients. In urine, 12 +/- 5% (mean +/- S.D.) of a given dose of citalopram was excreted in unchanged form. The propionic acid derivative was further conjugated, possibly to glucuronic acid. Mean steady-state plasma levels and metabolites in 24-h urine are given as percentages of the dose.

Comparative pharmacokinetics of metronidazole and tinidazole used as single dose prophylactic agents.

The pharmacokinetic properties of metronidazole (M) and tinidazole (T) were studied in patients undergoing colorectal surgery after a single preoperative dose of 1500 mg infused during 50 minutes. High-pressure liquid chromatography was used to determine serum concentrations, which for M and T were almost identical during the first 12 hours. After 24 hours, the concentration of T were slightly higher. Both drugs were detected in serum at 72 hours. The serum half-life (t1/2) was 9.4 hours for M and 17.6 hours for T, whereas the hydroxymetabolite of M had a t1/2 of 17.6 hours. There was considerable interindividual variation in both T and M concentrations. The prophylactic use of a single preoperative dose of 1500 mg of either M or T in elective colorectal surgery is supported by favourable pharmacokinetic properties of both drugs.

Pharmacokinetics and bioavailability of metronidazole after tablets, suppositories and intravenous administration.

The pharmacokinetics of metronidazole were determined in cross-over study on 11 healthy volunteers after 400 mg tablets from two producers. 1000 mg suppositories and 800 mg intravenously (IV). High-pressure liquid chromatography was used to assay both unchanged metronidazole (M) and the hydroxy metronidazole metabolite (OH-M). The peak concentrations were observed 1.2 - 1.3 hrs after the administration of tablets and 4.9 hrs after the suppositories. After the IV dose, the OH-M peak appeared only after 8 hours. The serum half-life was 6.5 hrs after the IV dose, 6.1 - 6.8 hrs after the tablets and 6.8 hrs after the suppositories. After IV dosage, the terminal phase distribution volume was 38.1 lit and the total body clearance 4.09 lit/hr. The bioavailability of the tablets was 80.4 and 84.1 per cent and after the suppositories 53.8 per cent. The rate of elimination OH-M was faster after suppositories than after IV dosage where it was intermediate after the tablets. Accordingly, the serum-half-life was 9.7 hrs after suppositories, 19.2 hrs after IV infusion, and 10.6 and 11.8 hrs. after the tablets. The rates of apparent metabolization was graded in the same relative order, with a faster rate after the suppositories, 0.168 hrs-1 compared to 0.368 hrs-1 after the IV route of administration. The differences pertaining to OH-M is considered probably to be caused by interaction with the metabolic activity of the bacterial flora of the colon.

Assay of metronidazole by HPLC compared with microbial method.

A high-performance liquid chromatography (HPLC) method for the assay of metronidazole and its 2-hydroxymethyl metabolite in sera was compared with a microbiological method, an agar well diffusion technique with Clostridium perfringens as indicator strain. The HPLC technique involves separation of metronidazole from its two active major metabolites (the 2-hydroxymethyl and the 1-carboxymethyl derivatives) on a mu-Bondapak C18 column and UV detection at 313 nm. The mobile phase was 35% acetonitrile in 0.02 M acetate buffer pH 4 with a low rate 2.0 ml/min. Tinidazole was used as an internal standard and metronidazole and its 2-hydroxymethyl metabolite quantitated by peak height ratios. The 1-carboxymethyl derivative was well separated from the other peaks. The HPLC procedure proved to be superior with respect to sensitivity (detection limits: 0-1 microgram/ml serum for both compounds), speed and precision. It discriminates between metronidazole and its two major active metabolites and quantitates the total amounts present. The microbial technique codetermines all antibacterial active compounds and monitors the free, not protein bound moieties. Published data on the activity of the 2-hydroxymethyl metabolite against Cl. perfringens relative to metronidazole and published results on the protein binding of metronidazole were used to correlate data from the two methods on individual serum samples collected during the early, intermediate and late periods after a single intravenous dose of metronidazole to volunteers.

Biliary excretion of bisacodyl and picosulphate in man: studies in gallstone patients after biliary tract surgery.

Bisacodyl (=BIS) and picosulphate (=PICO) have been given perorally to postoperative gallstone patients, who have undergone biliary tract surgery with the insertion of an indwelling T-tube. The doses corresponded to 7.7 mg of their common free diphenol desacetylbisacodyl (=DES). The bile was sampled in hourly fraction from the external limb of the T-tube; these fractions were analysed by a modification of the HPLC method previously used to study biliary excretion in the rat. In the BIS-patients (n=8), DES in conjugated form occurred in significant concentration already in the first fractions; peak excretion values equivalent to 4-8 microgram DES/ml bile were reached in 2-5 hours. Unchanged BIS could not be detected, and the concentration levels of unconjugated DES were insignificant. The PICO-patients (n=8) on the other hand showed low DES concentrations (conjugated + free less than or equal to 0.5 microgram DES/ml) in all fractions, or low initial concentrations followed by a more or less pronounced rise in the later fractions. These results are, qualitatively, as in the rat. However, the dose fractions excreted in bile (assuming a total hepatic output of 50ml/hours) seem smaller than those to be expected from rat experiments, at least as far as BIS is concerned.

Determination of the antidepressant agent citalopram and metabolites in plasma by liquid chromatography with fluorescence detection.

A high-performance liquid chromatographic method is described for the determination of citalopram [1-(3-(dimethylaminopropyl)-1-(4-fluorophenyl)-5-phthalancarbonitrile] and its two main metabolites (the methylamino and amino derivatives). The compounds were extracted from alkaline plasma with diethyl ether. The combined ether layers were evaporated after addition of 50 microliter of 0.1 N HCl. The residual extracts were purified with diethyl ether and 20 microliter were injected into a Spherisorb ODS 5-micrometer column with acetonitrile--0.6% phosphate buffer pH 3 (55:45, v/v) as the mobile phase. Using a fluorescence detector the detection limits are 1 ng/ml of plasma for citalopram and the methylamino metabolite and 0.5 ng/ml for the amino metabolite.

Enterohepatic circulation, urinary excretion and laxative action of some bisacodyl derivatives after intragastric administration in the rat.

Bisacodyl (BIS), the parent diphenol (DES) and its sulphuric acid di-ester (picosulphate = PICO) were given by stomach tube to fasted rats at a dose of 3.1 mumol/100 g rat. Bile was sampled in the periods 0-6, 6-12 and 12-18 hrs after drug administration, and assayed for total diphenol (= free + conjugated) by HPLC. Mean fractions (% of dose +/- S.E.M.) excreted in 5 rats per compound and period were: BIS 74.0 +/- 4.7, 51.9 +/- 7.9 and 30.8 +/- 2.5; DES 41.2 +/-4.3, 46.8 +/- 4.7 and 25.1 +/- 2.5; PICO 9.0 +/- 0.9, 26.0 +/- 5.4 and 19.6 +/- 3.1. Only minor amounts were excreted as free diphenol. Urine samples taken by bladder puncture and assayed as above furthermore showed that the renal excretion of total diphenol was insignificant compared to the amounts excreted in bile. Practically no diphenol was present in urine 0-6 hrs after the administration of PICO. In experiments with BIS and DES at 0.85 mumol/100 g, total diphenol excreted in bile during 0-6 hrs was: BIS 67.1 +/- 2.6 (n = 5); DES: 55.4 +/- 3.0 (5). - The latency time for laxative effect was studied in groups of 10 unfasted rats per compound. cumulative time response curves showed that PICO caused diarrhoea more promptly at 0.85 mumol/100 g than either BIS or DES. In most rats, this delayed action of BIS and DES persisted also at 1.7 mumol/100 g. At 3.1 mumol/100 g, however, the majority of the rats reacted as promptly to these two compounds as to PICO. These results are discussed in relation to the biliary excretion experiments, and interpreted in terms of the relative importance at the different dose levels of: 1. The enterohepatic recirculated fraction, and 2. The non-absorbed fraction, which passes directly to the large intestine. For PICO, the latter fraction is the single determinant of the effect, which is triggered when the di-ester is being hydrolyzed to active diphenol in this part of the GI-tract.

Quantitative structure-activity relationships in drug metabolism and disposition: pharmacokinetics of N-substituted amphetamines in humans.

Pharmacokinetic data of 15 N-alkyl-substituted amphetamines in humans have been the object of a retrospective quantitative structure-activity relationship study. The urinary excretion of amphetamines was shown to decrease with increasing lipophilicity; the correlation equations revealed that, for identical lipophilicities, tertiary amines are excreted faster than secondary amines, which are excreted faster than primary amines. The apparent n-heptane-pH 7.4 buffer partition coefficient correlates better with urinary excretion than does the true n-octanol-water partition coefficient, probably because it includes a pKa term that accounts for the fraction of the drug present in the tubules as nonionic species. The N-dealkylation rate increases with increasing lipophilicity of the substrates (enhanced enyzme affinity) but decreases with increasing bulk of the N-substituent that is split off (steric hindrance of initial C alpha-hydroxylation).

Determination of hydrochlorothiazide in serum by high-pressure liquid chromatography.

A quantitative high-pressure liquid chromatographic method has been developed for the analysis of hydrochlorothiazide in serum in therapeutical concentrations. The method is based on gel filtration of the sera on Sephadex G-15, extraction of the protein-free fraction of the effluent with ethyl acetate and injection of a methanol solution of the drug extract on a reversed-phase column packed with Spherisorb ODS (particle size, 10 mum). The mobile phase is 15% methanol in water. The detection limit is 50 ng/ml of serum. Serum samples from patients receiving hydrochlorothiazide have been analysed by the described method at different hours postdose.