Determinants of placental drug transfer: studies in the isolated perfused human placenta

There is little information on the effects of maternal and fetal placental blood flow rates, which can change independently, on the placental transfer rate of drugs of different placental permeabilities. We examined the effects of varying maternal and fetal perfusion flow rates on the placental transfer of three model compounds; antipyrine (high permeability), diclofenac (intermediate permeability), and cimetidine (low permeability) in the single-pass, dual-perfused lobule of the isolated human placenta. In variable flow ratio experiments (n = 9) fetal perfusate flow rate was held constant while a different maternal flow rate was used in each of five 25-min phases such that the maternal/fetal flow ratio ranged from 0.16 to 3.3. In constant flow ratio experiments (n = 4), the flow ratio was kept at 2.0, while maternal and fetal flow rates were varied from 4-18 and 2-9 mL/min, respectively. In the variable flow ratio experiments, the fetal transfer fraction (fetal venous/maternal arterial drug concentrations) varied approximately fivefold among the five phases for each of the three drugs. Therefore, placental transfer was flow dependent regardless of placental drug permeability. By contrast, in the constant flow ratio experiments, fetal transfer fraction was unchanged throughout the five phases for each of the three drugs. Of the various kinetic models that have been formulated to account for the different possible vessel geometries, the double pool flow model, which is a venous equilibrium model and predicts the least efficient drug transfer rate of those proposed, together with a small maternal arteriovenous shunt, produced the best fit overall.(ABSTRACT TRUNCATED AT 250 WORDS)

Quality of pharmacokinetic research in oncology

The usefulness of pharmacokinetically guided individualisation of drug therapy will depend, among other things, on the quality of the analytical and pharmacokinetic methods used. We surveyed the quality of analytical and pharmacokinetics methodology and reporting in a literature search of the oncology literature from 1987 to 1992, using the Medline database. Thirty articles that examined relationships between normal tissue toxicity and area under the plasma concentration-time curve (AUC) formed the study sample. Analytical procedures were adequately described in 77% of the articles, but details of validation of the assay were seriously deficient in the great majority of articles. Methods for calculation of AUC were also deficient in over half of the articles. The findings suggest that greater attention needs to be paid to the quality of pharmacokinetic investigation in oncology, otherwise progress in the use of pharmacokinetically guided individualisation of dosage may be hindered.

Serum lipid and glucose concentrations with a propofol infusion for cardiac surgery

OBJECTIVE

To document changes in serum lipids and glucose with a propofol infusion technique for cardiac surgery.

DESIGN

Prospective cohort.

SETTING

University teaching hospital.

PARTICIPANTS

22 elective cardiac surgical patients.

INTERVENTIONS

Frequent venous blood sampling.

MEASUREMENTS AND MAIN RESULTS

Serum lipids and glucose were measured at 10 time periods perioperatively, from preinduction until 4 hours post-cardiopulmonary bypass. Plasma propofol concentrations were also measured in 10 of these patients. There was a significant increase in glucose (P < 0.0005) and decreases in cholesterol (P < 0.0005), high-density lipoprotein (P = 0.004), and low-density lipoprotein (P < 0.0005); there was no significant change in triglycerides (P = 0.39). The propofol infusion resulted in acceptable plasma levels throughout the procedure and allowed early extubation in the intensive care unit, after a mean (SD) of 7.14 (5.9) hours. There was a strong correlation between triglyceride and propofol levels at most time periods (r = 0.38 to 0.98).

CONCLUSIONS

This study demonstrates that a propofol infusion technique does not result in elevation of serum lipids and supports its increased popularity in maintenance of anesthesia for cardiac surgery.

Right heart failure impairs hepatic oxygenation and theophylline clearance in rats

The effect of right heart failure on theophylline clearance was investigated in rats in which right ventricular pressure overload was produced by pulmonary artery constriction (PAC). Fifteen wk after the surgery, compared to sham-operated controls (n = 9), PAC rats (n = 9) showed markedly elevated mean central venous pressure (11 +/- 3 vs 1.44 +/- 0.88 mm Hg, P = .0001), and increased right ventricular weight (0.229 +/- 0.047 vs 0.124 +/- 0.013 g/100 g body weight, P = .0001). Centrilobular hepatic congestion was present in all PAC rats and total hepatic oxygen delivery was reduced significantly compared to controls (146 +/- 58 mumols/min vs. 206 +/- 28 mumol/min; P = .025). In the PAC group, theophylline clearance was reduced (0.82 +/- 0.12 ml/min vs. 0.96 +/- 0.13 ml/min in controls; P = .014), and there was a nonlinear correlation between theophylline clearance and total hepatic oxygen delivery (r = .82). These results suggest that in animals with PAC, metabolism of theophylline was impaired as a result of a reduction in total hepatic oxygen delivery. Therefore, in addition to the known effect of reduced hepatic blood flow on the hepatic clearance of "flow limited" drugs, reduction of hepatic oxygen delivery may be another important mechanism that can lead to reduction in hepatic clearance of capacity-limited drugs in congestive heart failure.

Oxygen supplementation restores theophylline clearance to normal in cirrhotic rats

BACKGROUND/AIMS

Capillarization associated with hepatic fibrosis may present a functional barrier to oxygen diffusion into the hepatocyte, and restriction on cellular oxygen supply may represent the rate-limiting constraint on hepatic oxidative drug metabolism. The aim of this study was to test this hypothesis by examining the effect of oxygen supplementation on plasma theophylline clearance in 10 control and 10 cirrhotic rats.

METHODS

Theophylline (3 mg/kg) was administered intravenously on two separate occasions, 24 hours apart, during which time the rats breathed either room air or oxygen (95%) from 1 hour before dosing until the end of plasma sampling with a randomized order of gas exposure.

RESULTS

Theophylline clearance was significantly reduced by a mean of 37% (n = 10; P = 0.003) in cirrhotic rats compared with controls. Oxygen supplementation significantly improved plasma theophylline clearance in cirrhotic rats by a mean of 40% (n = 10; P = 0.007), whereas clearance remained unchanged in healthy rats. Clearance in oxygen-supplemented cirrhotic rats was not significantly different from that in controls (P > 0.05).

CONCLUSIONS

These novel findings indicate an important role for hepatic oxygenation in improving drug disposition in cirrhosis, which may have potentially important clinical implications for the management of this disease.

Effects of chronic left ventricular failure on hepatic oxygenation and theophylline elimination in the rat

The effect of heart failure on the hepatic elimination of low-clearance drugs has not been clearly defined. We investigated the effect of left ventricular failure on theophylline clearance in rats. Cardiovascular function and theophylline pharmacokinetics were studied in conscious rats 6-8 weeks after left anterior descending coronary artery ligation. Rats with infarcts involving > 35% of the left ventricle (N = 9) had severe left ventricular failure, and, compared with control rats (N = 9), had reduced cardiac output (97.3 +/- 18.2 vs. 132 +/- 26 ml/min; p < 0.05), reduced mean arterial blood pressure (86 +/- 20 vs. 109 +/- 16 mm Hg; p < 0.05), markedly elevated left ventricular end-diastolic pressure (25.9 +/- 13.6 vs. 10.6 +/- 3.9 mm Hg; p < 0.01), and increased lung weight. There was also an increase in central venous pressure (6.44 +/- 2.60 vs. 3.67 +/- 2.60 mm Hg; p < 0.05), but no evidence of hepatic congestion, as judged by liver weights (14.7 +/- 1.5 vs. 15.3 +/- 1.3 g) and liver histology. However, total hepatic blood flow, total hepatic oxygen delivery, and theophylline clearance were found to be similar in both groups (1.66 +/- 0.30 vs. 1.75 +/- 0.38 ml/min/g liver weight; 12.4 +/- 1.8 vs. 13.3 +/- 3.7 mumol/min/g liver weight and 0.451 +/- 0.097 vs. 0.438 +/- 0.079 ml/min/100 g body weight), respectively. Taking the infarct group as a whole, total hepatic oxygen delivery was linearly correlated to theophylline clearance (r = 0.66, p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal hepatic propranolol metabolism. Studies in the isolated perfused fetal sheep liver

We have used an isolated perfused fetal sheep liver preparation to study the fetal hepatic metabolism of propranolol in vitro in the intact organ. Eight livers were perfused in situ via the umbilical vein in an oxygenated recirculating system at 300 ml/min. Radiolabeled 15-microns microspheres were used to quantify the hepatic ductus venosus shunt. Propranolol (4 mg) was dosed into the reservoir as a single bolus and perfusate and bile sampled over 150 min. Propranolol, 4-hydroxy propranolol (4OHP), 5-hydroxy propranolol (5OHP), desisopropylpropranolol (DIP), naphthoxylactic acid (NLA), and alpha-naphthoxyacetic acid (NAA) were assayed by HPLC, before and after deconjugation by enzyme hydrolysis. Mean age was 125 +/- 10 days, and mean liver weight was 66.1 +/- 18.8 g. Oxygen consumption (1.10 +/- 1.03 mumol/g/min), bile flow (0.51 +/- 0.18 microliters/g/min), and perfusion pressure (8.7 +/- 3.3 mm Hg) were stable. Ductus venosus shunt was 41.6 +/- 17.4% of umbilical vein flow. Propranolol clearance was 26.2 +/- 13.4 ml/min, and shunt-corrected extraction of propranolol was 0.26 +/- 0.13. The relative amounts of metabolites in perfusate after 150 min were: 4OHP (25.1%), 5OHP (5.08%) (ring-oxidation products), DIP (6.57%), and NLA (4.33%) (side-chain oxidation products). No alpha NAA (a product of N-dealkylation of NLA) was detected. Except for NLA, metabolites were present predominantly as conjugates. Biliary excretion of unchanged drug and metabolites accounted for a further 1.33% of the propranolol dose. These data indicate that, although the hepatic clearance and extraction of propranolol are low, the fetal sheep liver can metabolize propranolol by both ring- and side-chain oxidation reactions and can conjugate these metabolites.

Adults with spina bifida and/or hydrocephalus

Recent advances in medical technology enable many children with complex disabilities to survive into adulthood and to have certain expectations of life. One of these expectations is the continuity of specialist health care in an adult setting. This paper describes a new out-patient service which aims to provide optimum care, continuity and consistency of service for adults with spina bifida and/or hydrocephalus. The need for specialist health input into this service, in order to monitor the neurological, urological and psychosocial complications often associated with spina bifida and/or hydrocephalus is recognised. In one year (1992), 86 young adults with spina bifida and/or hydrocephalus attended for annual or more frequent assessment, either independently or with their families or carers. A variety of health and social problems were treated. In response to demand, a multi-disciplinary assessment unit, which includes the services of both medical and nursing specialists, occupational and physiotherapists, psychologists and access to specialist surgical opinions has recently opened at the Chelsea and Westminster Hospital. This new service attempts to meet some of the needs described in the outpatient audit. Adults with other disabilities are requesting to use this service. A longitudinal study to monitor quality, and outcome is indicated from this initial survey.

Effect of perfusate pH on reduction of quinidine capillary permeability by albumin in isolated perfused rat heart

It has been suggested that albumin reduces quinidine capillary permeability (PS) in the single-pass perfused heart preparation by reducing paracellular transport of quinidine ions. Using this preparation, we examined the effect of albumin (0.1 per cent) on quinidine PS at perfusate pH's of 7.1 and 7.9 during uptake of quinidine (19 microM) and also during washout of the drug using a randomized design. Quinidine PS was approximately 16 ml/min/g heart at pH 7.9 and was not altered by the presence of albumin in perfusate. At pH 7.1, in the absence of albumin, quinidine PS was also 16 ml/min/g, but in the presence of albumin (0.1 per cent) PS was reduced significantly to approximately 5 ml/min/g (P < 0.001). In the absence of albumin PS was the same at pH 7.1 and 7.9 in spite of a greater degree of ionisation of quinidine at pH 7.1. This suggests that there is significant uptake of ionised quinidine at pH 7.1. The greater effect of albumin on PS at pH 7.1 supports the hypothesis that albumin reduces paracellular transport of quinidine ions.

A longitudinal study of bacterial vaginosis during pregnancy

OBJECTIVE

To determine the longitudinal changes in the incidence of vaginosis in pregnancy.

DESIGN

A prospective study of women during pregnancy.

SETTING

A District General Hospital in North-West London.

SUBJECTS

Seven hundred and eighteen pregnant women attending antenatal clinics. At their first attendance and subsequently, Gram-stained vaginal smears were examined and Mycoplasma hominis and Gardnerella vaginalis were sought by culture.

RESULTS

Initially, 87 (12%) women had bacterial vaginosis diagnosed on Gram-stained reading of the vaginal smears. Examination of further smears, obtained from 176 women at 36 weeks of gestation, showed that those whose vaginal flora was normal initially, and who went to term, rarely developed vaginosis (three of 127, 2.4%). Samples were obtained at 36 weeks gestation from 32 women who had bacterial vaginosis initially, and went to term. In almost 50% (15 of 32) of these a normal lactobacillus-dominated flora had regenerated. Thirty-five women (5%) had initial vaginal smears graded as intermediate. From this group, six of the 17 (35%) women from whom samples were obtained at 36 weeks gestation still had flora of an intermediate pattern; 10(59%) now had normal flora and only one (6%) had developed bacterial vaginosis. Women with bacterial vaginosis were more likely to be culture-positive for M. hominis than those with normal flora (34/78 versus 10/563, odds ratio 42.73 (18.9 to 102.3) P < 0.001), or to be culture-positive for G. vaginalis than those with normal flora (35/78 versus 21/563, odds ratio 21.0 (10.75 to 41.2) P < 0.001).

CONCLUSION

Pregnant women do not commonly develop bacterial vaginosis after 16 weeks gestation, and if present, it remits spontaneously in approximately half of those who reach term. As bacterial vaginosis is associated with increased rates of second trimester miscarriage and preterm delivery, any treatment aimed at its eradication in pregnancy should be given no later than the beginning of the second trimester of pregnancy.

Hepatic uptake and excretion of [14C]sodium taurocholate by the isolated perfused fetal sheep liver

We have developed an in situ isolated perfused fetal sheep liver preparation to study fetal hepatic function free from the confounding influences of the mother and other fetal organs, and we have used the preparation to study the fetal hepatic clearance and biliary excretion of sodium taurocholate (TC). The viability and stability of this model were established by monitoring perfusion pressure, oxygen consumption, perfusate enzymes and electrolytes, the perfusate concentration ratio of lactate to pyruvate, bile flow, and liver histology. Perfusate delivery was 300 mL/min with a mean value of 3.94 mL/min/g liver (range: 2.46-6.72 mL/min/g liver). Gadolinium radiolabeled 15 microns microspheres were used to quantify the ductus venosus shunt through the liver and to determine relative flow rates between right and left hepatic lobes. TC was added to the reservoir either as a [14C]TC tracer bolus dose (2 microCi, N = 5) followed by a constant infusion of unlabeled TC, or as an initial bolus of [14]TC (54 mumol) followed by a [14C]TC constant infusion (30 mumol/hr, specific activity 30 microCi/mmol; N = 3). Perfusate samples were taken from the reservoir every 15 min and bile was collected in 30 min aliquots. Perfusion pressure (7.9 +/ 0.30 mmHg), perfusate potassium and oxygen consumption (0.9 +/- 0.07 mumol/min/g liver) were constant throughout, and the perfusate lactate/pyruvate concentration ratio was low (< 20). Liver histology showed no hypoxic changes. Bile flow fell slightly over the 150 min experiment time from 0.6 to 0.5 muL/min/g liver. These data indicate preparation viability and stability. The extent of the ductus venosus shunt was 16-66% (mean 35 +/- 6%) of umbilical vein flow, which correlated inversely with fetal gestational age (r = 0.94, P < 0.001). Relative flow to right and left lobes of liver was 1:1.4. In bolus dose experiments, TC t1/2 was 81.6 +/- 26 min, clearance (Cl) was 35.0 +/- 22.6 mL/min, shunt corrected extraction (E*) was 0.29 +/- 0.17 and biliary clearance (ClB) was 35.5 +/- 19.5 mL/min. In constant infusion experiments the corresponding results were Cl: 34.7 +/- 18.2, E*: 0.23 +/- 0.16, and ClB 32.7 +/- 17.7. The cumulative biliary excretion of [14C]TC in bolus dose experiments was 86.5 +/- 8.7% of the dose, and in constant infusion experiments, concentration of TC in bile was on average over 800 times that in plasma.(ABSTRACT TRUNCATED AT 400 WORDS)

Intracellular binding is an important determinant of the avid hepatic uptake of the high clearance drug omeprazole

The contribution of intracellular storage to hepatic uptake of the high clearance drug, omeprazole, was examined in the recirculating isolated perfused rat liver preparation. Following injection of [3H]omeprazole (7.5 microCi, 5 mg) into the portal vein over 1 min, livers were perfused for 5 min (N = 3) or 30 min (N = 3) and then homogenized at 4 degrees and fractionated by differential centrifugation. Radiolabelled omeprazole and metabolites were determined by scintillation counting of fractions of eluant from HPLC. Seventy per cent of drug had been taken up by the liver at 5 min and 85% at 30 min, with unchanged drug representing 43 and 7.4%, respectively, of drug taken up. At both times, 70-75% of intracellular unchanged drug and the major metabolites were located in the cytosol, and the cytosol:perfusate concentration ratio was approximately 10:1. Mitochondrial, lysosomal and microsomal fractions contained relatively little drug. Extensive cytosolic binding of omeprazole therefore contributes substantially to the initial avid hepatic first-pass uptake of this drug.

Product inhibition and dose-dependent bioavailability of propranolol in the isolated perfused rat liver preparation

We investigated in the isolated perfused rat liver (IPRL) whether product inhibition of metabolism contributes to the dose-dependent bioavailability of propranolol, a drug with a high, but saturable, hepatic first-pass effect. (+/-)-Propranolol was infused in the IPRL, using a recirculating design, for three 36-min periods (n = 9). Mean steady-state reservoir, i.e. hepatic inflow concentrations (Cin), were 4.97, 10.4, and 20.4 microM, respectively. Mean reservoir concentrations of the metabolites 4'-hydroxypropranolol, 5'-hydroxypropranolol, N-desisopropylpropranolol, and naphthoxylactic acid (NLA), a major side-chain-oxidation metabolite, increased disproportionately with propranolol dose, but their production rate did not reach steady state. In separate experiments (n = 4), perfusate containing 7.1, 12.8, and 21.6 microM (+/-)-propranolol, corresponding to administration rates of 114, 205, and 346 nmol/min, respectively, was passed through the liver for 30 min each using a single-pass design. The bioavailability (hepatic outflow concentration/Cin) of propranolol increased with Cin from 0.012 to 0.150 to 0.288 in the recirculating IPRL. In the single-pass IPRL the increase (0.0077 in 0.0669 to 0.136) was significantly less (P < 0.001). The greater bioavailability of propranolol in recirculating experiments was attributed to product inhibition since metabolites do not accumulate with the single-pass design. NLA did not appear to be the inhibiting metabolite because in further single-pass experiments with propranolol Cin of 21.6 microM the presence of NLA (21.6 microM) in perfusate had no effect on propranolol bioavailability (n = 7) compared with control experiments (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Lean body mass, body surface area and epirubicin kinetics

For a number of cytotoxics, a relationship between efficacy and plasma concentrations has recently been demonstrated. Lean body mass has been demonstrated to be a useful parameter for predicting drug clearance for a number of non-cytotoxic drugs. However, the role of lean body mass in predicting drug clearance for any cytotoxic drug has not been previously reported. Our purpose was to investigate lean body mass as a predictor of epirubicin clearance. Pharmacokinetic studies were performed in 10 patients receiving single agent epirubicin. Although preliminary, this study suggests that lean body should be further evaluated and tested in dose optimization studies.

Lean body mass as a predictor of drug dosage. Implications for drug therapy

There is mounting evidence to suggest that lean body mass (LBM) may be a better predictor of drug dosage than either total bodyweight (TBW) or body surface area (BSA), although the rationale for this is not clear. LBM, which is similar but not identical to fat-free mass, can be determined by many different methods. A simple equation based on TBW and height, or determination by bioelectrical impedance are probably the most suitable for use in drug disposition studies. Volume of distribution of relatively hydrophilic drugs correlates very well with LBM, with correlation coefficients of up to 0.9. LBM can be used to accurately predict the loading dose required for these drugs to attain a target peak plasma concentration. For lipophilic drugs, volume of distribution correlates better with TBW than with LBM. Investigation of the relationship between renal drug clearance and LBM has received little attention, probably because creatinine clearance is a useful and readily available marker of renal function. However, limited data suggest that creatinine clearance and LBM together may account function. However, limited data suggest that creatinine clearance and LBM together may account for more variability in renal clearance than creatinine clearance alone. For many drugs eliminated predominantly by the liver, there is a good correlation between systemic clearance and LBM. Such a correlation could be due to a correlation between systemic clearance and liver size or liver blood flow, which has been demonstrated for a few drugs, and a correlation between LBM and liver size and blood flow. The presence of a relationship between LBM and organ size and blood flow has, however, not been investigated to date. A good correlation between drug clearance and LBM indicates that LBM may be an accurate predictor of maintenance dosage, especially in obese patients, in whom there is a large discrepancy between LBM and TBW. BSA is an accurate predictor of drug dosage in infants and children, but whether LBM is superior to BSA in this population remains to be determined. In most studies in adults in which dosage based on LBM has been evaluated prospectively, LBM has been shown to be superior to other measures of body size as a predictor of drug dosage.

Hepatic Kupffer cell function: the efficiency of uptake and intracellular degradation of 14C-labelled mitochondria is reduced in aged rats

Uptake from the circulation and subsequent intracellular degradation of foreign and potentially harmful substances are key functions of hepatic Kupffer cells. While ageing is generally associated with decreased clearance by the reticulo-endothelial system, the effect of ageing on specific Kupffer cell functions is poorly understood. This study measured the ability of Kupffer cells of isolated perfused rat livers from young and old rats to both phagocytose and subsequently degrade exogenous radiolabelled mitochondria. Using electron microscopy and stereological techniques it was determined that there was no change in the volume density of Kupffer cells between 2 and 24 months, implying that the size of the Kupffer cell population increased (along with the total liver size) with age. However, despite this increase size there was no parallel increase in the capacity of the liver to take up or degrade radiolabelled mitochondria, implying that, in aged rats, Kupffer cell uptake and intracellular degradation was less efficient.

Influence of perfusion flow rate on uptake and pharmacodynamics of quinidine in isolated perfused rat heart

With the single-pass isolated perfused rat heart preparation, we examined the effect of perfusate flow rate on the time course of quinidine output concentration (Cout) and the change in the QT interval (delta QT) on the electrocardiogram. Four hearts were perfused at 5.6 mL/min with quinidine (20 microM) for 25-45 min. This was followed by a 50-min washout period with drug-free perfusate. This procedure was repeated four times in each heart. Using a one-compartment model, the rate constants calculated from the time course of Cout (k) and delta QT (Ke) were similar (p > 0.05) and did not vary among the five phases. A zero-time intercept for Cout indicated shunting of perfusate (1.2-13.6%), from which the coronary output concentration (Ccor) and coronary flow rate were calculated. These experiments were repeated in another six hearts, except flow rates of 2, 4, 6, 8, and 2 mL/min were used in each phase. Equilibration of Cout and delta QT was faster with increasing flow rate, and ke and k were similar at each flow rate (p > 0.05). A modified Kety-Renkin-Crone equation was fitted to values for k and coronary flow rate. The mean permeability surface product estimate was 15.3 +/- 3.0 mL/min/g heart, which in comparison with the highest flow rate used (9 mL/min/g heart) suggests that quinidine has intermediate permeability. The excellent fit obtained indicates that a more complex model, incorporating heterogeneous flows or opening of capillaries at higher flows, was not necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal bacterial colonisation of the genital tract and subsequent preterm delivery and late miscarriage

OBJECTIVE

To find out whether women with bacterial vaginosis detected early in pregnancy are at increased risk of preterm delivery.

DESIGN

Prospective description cohort study.

SETTING

Antenatal clinic in a district general hospital.

SUBJECTS

783 women examined during their first antenatal clinic visit and screened for recognised risk factors for preterm delivery and the presence of bacterial vaginosis or intermediate abnormal flora detected by examination of a vaginal smear stained by Gram's method.

MAIN OUTCOME MEASURES

Gestational age at delivery classified as late miscarriage (16-24 weeks' gestation), preterm delivery (24-37 weeks' gestation), term delivery (> or = 37 weeks' gestation).

RESULTS

Multiple logistic analysis showed that there was an increased incidence of preterm delivery in women with a previous preterm delivery (9/24; odds ratio 25; 95% confidence interval 9 to 70; P < 0.001) and bacterial vaginosis (9/115; 2.8; 1.1 to 7.4; P = 0.04). A further logistic analysis of data from women recruited before 16 weeks' gestation showed that preterm deliveries or late miscarriages occurred more often in women with bacterial vaginosis (12/77; 5.5; 2.3 to 13.3; P < 0.001).

CONCLUSIONS

Late miscarriage and preterm delivery are associated with the presence of bacterial vaginosis in early pregnancy. This is independent of recognised risk factors such as previous preterm delivery.

Albumin decreases myocardial permeability of unbound quinidine in perfused rat heart

With the single-pass, isolated, perfused rat heart preparation, we examined the effect of different perfusate albumin concentrations on the capillary permeability and pharmacodynamic effects of quinidine. Nine hearts were perfused for five consecutive 35-min phases with buffer containing quinidine and albumin concentrations of 0%, 0.1%, 1%, 6% and 0%, in that order, with a 55-min washout between each phase. Compared with 0% albumin perfusate, the equilibrium rate of quinidine perfusate output concentration (Cout) was slower with 0.1% albumin but faster with 1% and 6% albumin. Quinidine Cout, unbound fraction (fu) and perfusion flow rate (Q) for each phase of each experiment were fitted by a modified Kety-Renkin-Crone equation. Estimates of the capillary permeability-surface product (PS) for the two 0% albumin phases (14.4 +/- 5.6 and 12.3 +/- 4.4 ml/min) were significantly higher than those for the three albumin phases (5.3 +/- 1.0, 6.7 +/- 1.2 and 7.4 +/- 2.2 ml/min, respectively; P < .05). There was a direct, linear relationship between lengthening of the QT interval of the ECG and total and unbound quinidine concentrations, but the relationship for unbound concentration was independent of fu, showing that the pharmacodynamic effect was mediated by unbound concentration. In four additional experiments with antipyrine instead of quinidine, PS for the two 0% albumin phases (24.7 +/- 6.5 and 23.2 +/- 2.4 ml/min) was not significantly different than that for the three albumin phases (25.5 +/- 6.1, 22.5 +/- 2.9 and 22.9 +/- 3.6 ml/min, respectively). Albumin had no effect on the volume of distribution referenced to unbound drug for either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alpha 1-acidglycoprotein on myocardial uptake and pharmacodynamics of quinidine in perfused rat heart

The myocardial uptake and pharmacodynamics of quinidine were examined in the isolated perfused rat heart preparation under conditions of varying concentrations of bovine alpha 1-acidglycoprotein (AAG) in the perfusate. Three hearts were perfused for five consecutive 35 min phases with buffer containing quinidine and AAG in concentrations of 0, 0.1, 0.5, 1.5 and 0 g/L, in that order, with a 55 min washout period between each phase. The equilibration rate constant for the quinidine output concentration increased with increasing AAG concentration, but not as much as predicted by the conventional pharmacokinetic uptake model, which assumes constant capillary permeability among the phases. Estimates of the permeability surface product for the two zero AAG phases (17.7 +/- 1.91 and 19.1 +/- 0.82 mL/min/g) were significantly greater than those for the three AAG phases (8.94 +/- 0.99, 8.70 +/- 0.26, 9.01 +/- 0.26 mL/min/g; P < 0.05). This effect of AAG is the same as that observed previously by us with bovine serum albumin in this same experimental preparation. This suggests that the mechanism of reduced capillary permeability is the same for both proteins, i.e., the formation of a steric barrier to paracellular transport rather than an electrostatic barrier. There was a direct, linear relationship between lengthening of the QT interval of the electrocardiogram and total and unbound quinidine concentrations, but the relationship for unbound concentration was independent of quinidine unbound fraction. Therefore, the electrocardiogram effect of quinidine was directly related to the circulating unbound rather than total drug concentration.

Simple direct injection high-performance liquid chromatographic method to determine quinidine in plasma

High-performance liquid chromatographic methods that use direct injection of plasma include column-switching procedures, modified mobile phases and small-pore modified stationary phases. By using a large-pore (300 A) Selectosil C18 column, developed for the analysis of macromolecules, we have shown that quinidine in plasma and protein solutions can be assayed accurately and rapidly by directly injecting 2 microliters plasma or protein solution onto the column. Column life is not reduced, and the limit of quantitation is 0.01 microM.

Influence of albumin on isoprenaline and propranolol effects on isolated rat uterus

We investigated the effect of albumin (6%) on the (+/-)-isoprenaline-induced relaxation of strips of isolated rat uterus and its antagonism by (-)-propranolol. The mean isoprenaline EC50 in the presence of albumin was significantly less than that in the absence of albumin (geometric mean 1.94 +/- 3.33 versus 3.21 +/- 3.50 nM, respectively; n = 14; p = 0.006, paired t test). This indicates enhancement of isoprenaline activity by albumin which could not be explained by protein binding, as this would have reduced activity. Geometric mean control KB values for inhibition of isoprenaline by propranolol at 26.8 and 500 nM were 0.835 +/- 1.68 (n = 10) and 0.889 +/- 1.60 nM (n = 34), respectively. In the presence of 6% albumin, KB for propranolol was increased significantly to 13.3 +/- 1.8 nM (n = 27, p < 0.001). Calculation of KB in terms of the measured propranolol unbound concentration of 26.8 nM, after taking into account the lower isoprenaline EC50 in the presence of albumin, yielded a mean value of 0.725 +/- 1.86 nM, which was not significantly different from either control (p > 0.05). Therefore, propranolol activity was as predicted by the unbound drug concentration in contrast to isoprenaline activity. We conclude that albumin can alter in vitro drug activity by mechanisms in addition to the reduction of unbound drug concentration.

Protection of three strains of mice against lethal influenza in vivo by defective interfering virus

This report examines the protective effects of defective interfering (DI) WSN on three strains of mice (C3H/He-mg (H-2k), C57BL/6 (H-2b) and BALB/c (H-2d)) infected with various doses of A/WSN influenza virus. All three strains were protected in terms of morbidity and mortality, to varying extents, DI WSN protected optimally against a low but lethal dose of A/WSN in C3H/He-mg mice, but also protected this and other strains against very high doses of A/WSN. Intermediate sized inocula gave little, if any, protection. In all cases protection required an active DI genome since inactivation with beta-propiolactone abrogated any sparing effect. Consolidation of the lungs was reduced by treatment with active DI virus, but at some doses of inoculum there was reduction in lung pathology without reduction of mortality. Treatment of infected mice with DI virus did not reduce the lung virus titre, but in C3H/He-mg mice resulted in recovery of infectious virus from other tissues, notably the heart, where it was not normally found. No infectivity was recovered from brain, liver or serum. Haemagglutination-inhibiting (HI) antibody could not be detected in the lungs of any of the infected mice co-inoculated with the control BPL-inactivated DI WSN but was present in considerable amounts in all three strains when these were co-inoculated with DI virus. These and previous data (Morgan and Dimmock, 1992) suggested that influenza virus was immunosuppressive and that active DI virus abrogated these suppressive effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of pH on the uptake and pharmacodynamics of quinidine in the isolated perfused rat heart

Using the single-pass isolated perfused rat heart preparation we examined the effect of perfusate pH (pH 7.05, 7.46, 7.71, 7.92) on quinidine output concentration (C(out)) and delta QT. Eight hearts were perfused at 2.5 ml/min. with quinidine (20 microM) for 35 min. followed by a 35-40 min. washout period with drug-free perfusate. This procedure was repeated four times in each preparation with the pH sequence varied and the same pH used in the first and last phases. Increasing pH slowed the rate of equilibration of C(out), the equilibration rate constant (k) decreasing from 0.273 min.-1 at pH 7.05 to 0.095 min.-1 at pH 7.92. A modified Kety-Renkin-Crone equation was fitted to the C(out) versus time data for each pH. The estimated volume of distribution (V) increased significantly with pH from 11.5 +/- 1.1 to 32.5 +/- 2.9 ml/g, but the permeability surface product did not change with pH (mean 17.7 ml/min./g). There was a linear relationship between V and calculated un-ionised quinidine C(out), with an intercept of 5.70 ml/g corresponding to the V of ionised drug. This indicates that ionised and un-ionised drug readily enter the heart and that the slower equilibration with pH is due to the increased V which results from increased partitioning of un-ionised quinidine into myocardial tissue. Perfusion pH did not directly affect baseline QT interval, but the rate of attainment of maximum delta QT decreased with increasing perfusate pH. Plots of delta QT versus calculated coronary output quinidine concentration did not change with pH, showing that this drug effect was due to both ionised and un-ionised moieties. This study shows that myocardial permeability and pharmacodynamic effect (delta QT) of quinidine are not influenced by perfusion pH over the range 7.0 to 7.9, although rate of equilibration of both C(out) and effect vary with pH.