Plasma concentration of topically applied betaxolol in elderly glaucoma patients.

Our aim was to study the concentration of betaxolol in plasma after its topical ocular use during the normal 12 hr dosing interval. Twenty microliters of betaxolol 0.5% solution were applied into both eyes of nine glaucoma patients, and the plasma concentrations of the drug were measured 12 hr thereafter using a radioreceptor assay. The same amount of betaxolol was then applied ocularly, and its concentration in plasma was measured at 5, 10, 15, 30 min and 1, 2, 4 and 8 hr thereafter. The mean (SD) concentration of betaxolol in plasma twelve hr after the first dose was 0.4 (0.2) ng/ml. After the second dose, the patients showed a biphasic concentration vs. time curve, the first peak occurring at 8 (4) min, and the second peak at 210 (132) min; the mean (SD) peak concentrations being 1.1 (0.3) and 2.0 (1.1) ng/ml, respectively. The area under the concentration vs. time curve showed a 4-fold variation among our patients. Topically applied betaxolol was rapidly absorbed into systemic circulation, and concentrations were detectable even at 12 hr. The interindividual variation in the systemic absorption of betaxolol was large.

Wound healing in denervated rat groin skin flap.

The purpose of the present study was to investigate the effect of denervation on dermal wound healing in rat groin skin flaps for 1-10 weeks. The structural differences between wounds in normal and in denervated skin were investigated histologically using Herovici's staining. Pro alpha1(I) collagen mRNA levels were studied using Northern hybridization. Denervation and reinnervation of the skin flaps was demonstrated with quantitative noradrenaline determination and immunohistochemically using neurofilament and S-100 antibodies. Denervation of the skin did not seem to have any apparent effects on wound healing as assessed by light microscopy. There were no significant differences in pro alpha1(I) collagen mRNA levels either. The thin muscle layer underlying the skin was the only element that clearly responded to the denervation.

Influence of hydroxychloroquine on the bioavailability of oral metoprolol.

AIMS: Hydroxychloroquine (HCQ) is used widely in the treatment of chronic inflammatory diseases such as rheumatoid arthritis. Since there is great interindividual variability in the pharmacokinetics of HCQ and chloroquine is a potent inhibitor of CYP2D6-catalysed pathways in vitro, we wished to study the interaction of HCQ with CYP2D6-mediated metabolism of other drugs in vivo. METHODS: Metoprolol and dextromethorphan (DM) were selected as probe drugs because they are well-studied and widely used test substrates of CYP2D6. In this randomized, double-blind crossover study, seven healthy volunteers with extensive metabolizer phenotype for CYP2D6 ingested either 400 mg hydroxychloroquine or placebo daily for 8 days after which single oral dose pharmacokinetics of metoprolol were investigated. Dextromethorphan metabolic ratio (DM-MR) was also determined at baseline and after the ingestion of HCQ or placebo. RESULTS: Concomitant administration of HCQ increased the bioavailability of metoprolol, as indicated by significant increases in the area under the plasma concentration-time curve (65 +/- 4.6%) and maximal plasma concentrations (72 +/- 6.9%) of metoprolol. While the DM-MR values were not significantly changed, the phenotypic classification of one individual, who was heterozygous for a mutant CYP2D6 allele, was converted to a poor metabolizer by HCQ administration. CONCLUSIONS: HCQ inhibits metoprolol metabolism most probably by inhibiting its biotransformation by CYP2D6. The inhibitory effect of HCQ on dextromethorphan metabolism was not apparent when DM-MR was used as an indicator, except in an individual with limited CYP2D6 capacity.

Non-adrenergic binding of [3H]atipamezole in rat kidney--regional distribution and comparison to alpha2-adrenoceptors.

1 Atipamezole (4-(2-ethyl-2,3-dihydro-1H-inden-2-yl)-1H-imidazole) was first introduced as a potent and specific alpha2-adrenoceptor antagonist, but in some tissues [3H]atipamezole identifies an additional population of binding sites, distinct from both classical alpha2-adrenoceptors and I1- and I2-imidazoline receptors identified with [3H]para-aminoclonidine or [3H]idazoxan. 2 In the present study we have characterized [3H]atipamezole binding sites in rat kidney by receptor autoradiography and membrane binding assays and determined whether they are pharmacologically identical with the previously described binding sites for [3H]para-aminoclonidine and [3H]idazoxan. [3H]RX821002 and [3H]rauwolscine were used to compare the regional distribution of alpha2-adrenoceptors to that of non-adrenergic binding sites of [3H]atipamezole. 3 Comparative autoradiographic experiments demonstrated the differential localisation of [3H]atipamezole, [3H]RX821002 and [3H]rauwolscine binding sites in rat kidney. The pattern of distribution of non-adrenergic [3H]atipamezole binding sites is clearly distinct from that of alpha2-adrenoceptors. 4 The non-adrenergic binding of [3H]atipamezole in rat kidney does not fall into any of the previously identified three classes of imidazoline receptors studied with [3H]para-aminoclonidine, [3H]idazoxan and [3H]RX821002. 5 Atipamezole had no inhibitory effect on MAO-A or MAO-B activity in renal membranes, which speaks against the involvement of MAOs in the observed radioligand binding.

Comparison of the effects of moclobemide and selegiline on tyramine-evoked mydriasis in man.

AIMS: To examine the feasibility of using the human iris in vivo for the assessment of the interaction between tyramine and monoamine oxidase (MAO) inhibitors. To examine the relative roles of the two forms of MAO in terminating the response to sympathomimetic amines in the iris, by comparing the effects of single oral doses of moclobemide, a selective MAO-A inhibitor, and selegiline, a selective MAO-B inhibitor, on mydriatic responses to tyramine. METHODS: Twelve healthy male volunteers participated in three monthly sessions, each associated with ingestion of one capsule (moclobemide 450 mg, selegiline 10 mg, or placebo), according to a double-blind, balanced, cross-over design. Tyramine hydrochloride eye-drops (75 mM, 2 x 10 microl) were instilled three times in the left conjuctival sac at 40 min intervals. Pupil diameter was monitored with a binocular infrared television pupillometer before and for 4.5 h after ingestion of the capsule. The pupillary response to tyramine was expressed as the area under the pupil diameter x time curve (arbitrary units). A blood sample was taken before and 2 h after ingestion of the capsule, for the assay of platelet MAO-B activity, and plasma 3,4-dihydroxyphenylglycol (DHPG) concentration, an index of MAO-A activity. Platelet MAO activity was assayed radiochemically, using [14C]-phenylethylamine as substrate, and plasma DHPG by high performance liquid chromatography (h.p.l.c.). The results were analysed using analysis of variance with repeated measures, followed by Bonferroni's corrected t-test, using a significance criterion of P < 0.05. RESULTS: Both moclobemide and selegiline, compared with placebo, caused significant miosis in the right (untreated) eye. The changes in pupil diameter (mm +/- s.e. mean) from the pretreatment measurement were: placebo -0.09 +/- 0.07, moclobemide -0.52 +/- 0.09, selegiline -0.26 +/- 0.1. The mydriatic response to tyramine was potentiated by moclobemide, compared with the response recorded in the presence of placebo. The responses to tyramine (arbitrary units +/- s.e. mean) were: placebo 77.08 +/- 11.65, moclobemide 140.25 +/- 18.9, selegiline 72.75 +/- 12.35. Both moclobemide and selegiline significantly reduced platelet MAO activity, compared with placebo. The changes in platelet MAO activity (nmol h(-1) mg(-1) protein +/- s.e. mean) from the pretreatment level were: placebo 0.5 +/- 0.62, moclobemide -6.7 +/- 0.66, selegiline -17.7 +/- 0.87. Moclobemide significantly reduced plasma DHPG concentration, compared with placebo. The changes in plasma DHPG concentration (nmol l(-1) +/- s.e. mean) from the pretreatment level were: placebo -0.01 +/- 0.24, moclobemide -4.98 +/- 0.32, selegiline -0.51 +/- 0.26. CONCLUSIONS: The potentiation of tyramine-evoked mydriasis by moclobemide is likely to reflect the inhibition of MAO-A activity in the iris, consistent with the activity of this enzyme in sympathetic nerve terminals. The lack of effect of selegiline on tyramine-evoked mydriasis argues against a role of MAO-B in terminating the effects of sympathomimetic amines in the iris. The effects of the two drugs on platelet MAO activity and plasma DHPG concentration are in agreement with previous reports and consistent with the relative selectivity of moclobemide for MAO-A and of selegiline for MAO-B. The miosis caused by the two MAO inhibitors is likely to be due to a central sympatholytic action of the drugs.

Inhibition of platelet monoamine oxidase type B by selegiline.

Selegiline is an irreversible inhibitor of monoamine oxidase type B (MAO-B). No comparative data are available on the MAO-B inhibition caused by orally and intravenously administered selegiline. This study aimed to clarify this matter and to investigate the dose-response of MAO inhibition caused by orally administered selegiline. Sixteen healthy volunteers were given selegiline as a single intravenous dose (0.5 mg) and in three low oral doses (0.5 mg, 1.0 mg, and 1.5 mg) in an open-label randomized crossover trial. The MAO-B inhibition after the 0.5-mg intravenous dose was 79.6 +/- 15.1%. The dose-response of the three oral doses causing MAO-B inhibition was logistic. To check whether this equation could be applied to higher doses, eight of the volunteers were given 5-mg and 10-mg oral doses. The MAO-B inhibition after these doses (84.9 +/- 11.9% and 95.6 +/- 4.5, respectively) fitted well with the logistic model. With this equation obtained, it was calculated that a 3.4-mg oral dose of selegiline would be needed to obtain the same degree of MAO-B inhibition as after the intravenous dose of 0.5 mg. Therefore, the ratio of MAO-B inhibitory potential of intravenously and orally given selegiline is approximately 7 to 1, which fits well with the low bioavailability of the drug after oral administration.

Desmethylselegiline, a metabolite of selegiline, is an irreversible inhibitor of monoamine oxidase type B in humans.

Selegiline, an irreversible and selective inhibitor of monoamine oxidase type B (MAO-B), is metabolized into desmethylselegiline, levomethamphetamine, and levoamphetamine. In animal experiments, desmethylselegiline also has been shown to be an irreversible inhibitor of MAO-B. This study investigated the inhibitory potential of MAO-B and the pharmacokinetics of desmethylselegiline in humans. A double-blind, crossover trial was performed to compare the effects of a single dose (10 mg) of selegiline or desmethylselegiline on MAO-B platelet activity. The urinary excretion of phenylethylamine, which is considered to be a parameter of MAO-B inhibition, also was measured. The concentrations of selegiline, desmethylselegiline, and their metabolites were measured in plasma after administration of the two compounds. Ten healthy volunteers participated in the study. There was a clear inhibition of platelet MAO-B by both compounds. Desmethylselegiline caused a 63.7 +/- 12.7% inhibition of platelet MAO-B compared with 96.4 +/- 3.9% caused by selegiline. The maximal inhibition by desmethylselegiline was reached significantly later after desmethylselegiline (time to reach maximal inhibition [tmax], 27 +/- 20 hours) than after selegiline administration (tmax, 1.4 +/- 1.4 hours). The platelet MAO-B activity returned to baseline levels within 2 weeks, thus reflecting the irreversible nature of the inhibition by both compounds. The cumulative 48-hour excretion of phenylethylamine was 33% lower after desmethylselegiline than after selegiline administration. All three major metabolites of selegiline could be detected in plasma after selegiline administration. Levoamphetamine was the only metabolite of desmethylselegiline. The area under the concentration-time curve from time 0 to 24 hours (AUC0-24) of desmethylselegiline was 33 times higher than that of selegiline, suggesting a better bioavailability of desmethylselegiline. Desmethylselegiline is an orally active, irreversible inhibitor of MAO-B and could possibly be used to treat Parkinson's disease in the same way as selegiline.

Aryl hydrocarbon hydroxylase activity in spontaneous mammary tumors in rat.

The development of spontaneous mammary tumors was observed for about 2 years in a group of 25 female Sprague-Dawley rats aged over 1 year at the beginning of the study. All younger females in our animal facility were similarly monitored. In old females, the incidence of spontaneous mammary tumors was 64%. The parity of rats did not protect them from tumorigenesis, but the proportion of malignant tumors was higher in virgin (57%) than in parous (13%) rats. Activities of cytochrome P450IA1-dependent enzyme (aryl hydrocarbon hydroxylase, AHH) and NADPH-cytochrome P450 reductase (NCR) were determined in microsome fractions isolated from livers, lungs, uteri and tumors of rats. AHH and NCR activities in tumors and uteri were low compared to those in livers or lungs. In tumors, the activity distributions were wide, even in different tumors of the same animal the AHH activities varied as widely as between different animals. The activities in benign and malignant tumors were not statistically significantly different. No correlation with liver, lung or uterine activities was found either. With ageing of the rat, the AHH activities in tumors, liver and lungs decreased. The behavior of AHH in spontaneous mammary tumors in rats seems to be similar to that found in chemically induced tumors and seems to show individual regulation, possibly altered by tumorigenesis in each individual tumor.

Aryl hydrocarbon hydroxylase activity in chemically induced and toremifene-treated mammary tumors in rats.

Aryl hydrocarbon hydroxylase (AHH) and NADPH-cytochrome P450 reductase (NCR) activity of microsomes from liver, lungs, uterus and mammary tumors in dimethylbenzanthracene-induced and toremifene-treated female Sprague-Dawley rats were studied. AHH and NCR activity in tumors and uteri was low compared with that in livers and lungs. The distribution of AHH in tumors was wide and skewed. It varied in different tumors of the same animal as widely as between different animals. The enzyme activity in tumors did not correlate with that in the liver, lungs or uterus of the same animal. Toremifene had no effect on AHH or NCR in tumor or liver, but it decreased them in lungs. Tumor AHH activity correlated with its overall growth rate and development stage. The results suggest that malignant transformation leading to the defect in growth regulation also confuses the complex regulatory system of AHH activity.

Cytochrome P450IA1 activity in human myometrium and uterine leiomyoma: influence of smoking.

A xenobiotic-metabolizing enzyme, the P450IA1 (aryl hydrocarbon hydroxylase; AHH) was measured fluorometrically in myometrium and in uterine leiomyoma tissues. The material included both myometrium and leiomyoma tissue samples from 62 leiomyoma patients and 22 tissue samples of normal myometrium obtained from leiomyoma-free patients undergoing hysterectomy. Among 62 leiomyoma patients there were 14 cigarette-smokers and 48 non-smokers, and among 22 control patients 6 and 16, respectively. The P450IA1 activity of the leiomyomas was significantly (P < 0.0005) higher than that of the surrounding myometrium in both smoker and non-smoker groups. In smokers, myometrium an obvious induction of P450IA1 was seen. Smoking increased the P450IA1 activity also in the leiomyoma, but the increase was not statistically significant. Our study supports the idea that myometrial tissue can respond to xenobiotics from the environment.

Findings on lipid peroxidation and antioxidant function in hypertensive complications of pregnancy.

OBJECTIVE: To assess lipid peroxidation and antioxidant function in hypertensive complications of pregnancy. DESIGN: Cross sectional study comparing pre-eclamptic and control patients. SETTING: Tampere University Hospital, Finland. SUBJECTS: Twenty healthy women with normal, uncomplicated pregnancy; 23 women with severe pre-eclampsia; 20 women with mild pre-eclampsia; and 13 women with pregnancy-induced hypertension. MAIN OUTCOME MEASURES: Conjugated dienes; thiobarbituric acid--reactive material or malondialdehyde (MDA); fluorescent chromolipids (FCL); glutathione peroxidase (GSHPx); selenium; uric acid; and vitamin E. RESULTS: Lipid peroxidation assessed by the appearance of conjugated dienes and malondialdehyde was significantly increased in the hypertensive patients as compared with control patients. Lipid peroxidation products also showed high correlation to the level of blood pressure, but failed to show significant relation to the outcome of the fetus. The activities of erythrocyte and plasma glutathione peroxidase were increased in severe pre-eclampsia, and high levels of plasma or platelet glutathione peroxidase were found to have some association with fetal growth retardation or asphyxia. CONCLUSIONS: Our findings give support to those few studies considering lipid peroxidation as an important factor in the pathogenesis of pre-eclampsia. The rise in antioxidants is probably of compensatory nature responding to the increased peroxide load in pre-eclampsia and may reflect the severity of the disease.

Metformin and liver glycogen synthase activity in obese Zucker rats.

The effect of chronic treatment with metformin (320 mg/kg/day) on plasma glucose and insulin as well as liver glycogen synthase activity and hepatic glycogen content was studied in obese hyperinsulinemic Zucker rats. Metformin significantly reduced both plasma glucose (by 10%) and insulin levels (by 39%) at fasting but had no effect on hepatic glycogen content or on the basal activity of liver glycogen synthase.

Pregnancy-induced hypertension is associated with changes in maternal and umbilical blood antioxidants.

Seventeen pregnancies with pregnancy-induced hypertension (PIH) and 28 control pregnancies were analyzed with regard to maternal and fetal blood antioxidants and lipid peroxidation products (conjugated dienes). In PIH, maternal blood levels of conjugated dienes were higher than in normal pregnancy. Also the activities of platelet and plasma glutathione peroxidase (GSHPx) were higher in PIH. In umbilical cord blood, the appearance of conjugated dienes, the concentration of vitamin E and the activity of erythrocyte GSHPx were lower than the corresponding maternal values. There was no difference between PIH and normal pregnancy in the appearance of conjugated dienes in cord blood, but erythrocyte GSHPx and plasma vitamin A were lower in PIH. Cord blood plasma vitamin A showed a negative correlation to maternal mean arterial pressure. We suggest that lipid peroxidation is involved in the pathogenesis of maternal PIH, and it may also have effects on the vascular function and antioxidant status of the fetus.

The pharmacokinetics of mecillinam and pivmecillinam in pregnant and non-pregnant women.

1. The pharmacokinetics of parenteral mecillinam (n = 27) and oral pivmecillinam (n = 12) were studied in pregnant (n = 27) and non-pregnant (n = 12) subjects. 2. In early pregnancy (9-14 weeks of gestation) the mean peak plasma drug concentration (Cmax = 19 +/- 9 micrograms ml-1) after an intravenous injection of 200 mg mecillinam was significantly lower (P less than 0.05) and the volume of distribution (V = 49 +/- 20.1) significantly larger (P less than 0.05) than in non-pregnant subjects (Cmax = 35 +/- 18 micrograms ml-1, V = 29 +/- 12.1). In late pregnancy (39-40 weeks of gestation) the plasma mean peak concentration (Cmax = (29 +/- 14 micrograms ml-1) after parenteral administration of 200 mg mecillinam was slightly lower and the volume of distribution (V = 65 +/- 29.1, V = 0.9 +/- 0.4 l kg-1) significantly larger than that in non-pregnant subjects (V = 0.4 +/- 0.3 l kg-1). Also after oral administration of 200 mg pivmecillinam, equimolar to 136.5 mg mecillinam, the mean peak plasma concentration in pregnant subjects (Cmax = 1.8 +/- 1.2 micrograms ml-1) was slightly lower than that in non-pregnant subjects (Cmax = 1.7 +/- 1.2 micrograms ml-1). 3. The mean half-life of elimination after parenteral administration of mecillinam was significantly longer during both early (t1/2,Z = 133 +/- 38 min, P less than 0.05) and late pregnancy (t1/2,Z = 107 +/- 41 min, P less than 0.05) as compared with the non-pregnant state (t1/2,Z = 75 +/- 21 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of chloroquine absorption by activated charcoal.

1. The ability of activated charcoal to prevent the absorption of chloroquine was investigated in healthy volunteers, and the effect of the charcoal-chloroquine ratio on the completeness of binding was studied in vitro. 2. After an overnight fast, six subjects ingested 500 mg of chloroquine phosphate with water, and another group of six subjects ingested 25 g of charcoal suspension within 5 min of chloroquine intake. The concentrations of chloroquine in plasma and whole blood were measured by high-performance liquid chromatography for 192 h. 3. Activated charcoal reduced the areas under the plasma and whole blood chloroquine concentration-time curves (AUC) from 0 to 192 h, the total AUCs, and the peak concentrations by 99% (P less than 0.001). 4. Chloroquine was very effectively bound by activated charcoal in vitro, even at low charcoal-chloroquine ratios. For example, at a ratio of 5:1, about 98% of chloroquine was bound. 5. Activated charcoal should be very effective in reducing the absorption of that fraction of chloroquine dose which is in the stomach at the time of charcoal administration. Because the acute toxicity of chloroquine is extremely high and death usually occurs within 1-3 h of overdosage, charcoal should be given as early as possible in suspected chloroquine intoxication.

Lipid peroxidation products, selenium-dependent glutathione peroxidase and vitamin E in normal pregnancy.

Twenty healthy women with normal pregnancy were simultaneously analysed with regard to lipid peroxidation products, selenium-dependent glutathione peroxidase and vitamin E. Conjugated diene double bonds, fluorescent chromolipids and thiobarbituric acid-reactive material were analysed as breakdown products of lipid peroxidation. The level of conjugated dienes in serum rose more than 45% when pregnancy advanced from the first to second trimester, but after that it declined almost to the same level as in the first trimester. The fluorescent chromolipids tended to behave in the same way. While the lipid peroxidation products reached their highest level in the second trimester, the activity of glutathione peroxidase rose progressively till the third trimester both in erythrocytes and platelets, in spite of the stable concentration of selenium in blood and plasma. The concentration of vitamin E in serum rose progressively till the end of pregnancy, but in the relation of vitamin E to cholesterol only a slight rising tendency was noted. We suggest that in normal pregnancy lipid peroxidation is controlled by adequate antioxidative response.

Activity of xenobiotic metabolizing liver enzymes in Zucker rats.

The activity of four liver enzymes participating in the xenobiotic metabolism was determined in male and female obese hyperinsulinemic Zucker rats. When compared to lean normoinsulinemic control animals the obese male rats had lower hepatic aryl hydrocarbon hydroxylase and the female animals lower 7-ethoxycoumarine O-deethylase and N-nitrosodimethylamine N-demethylase activities. The results contrast those reported in the literature for hypoinsulinemic streptozotocin diabetic rats.

Is aryl hydrocarbon hydroxylase activity a new prognostic indicator for breast cancer?

Aryl hydrocarbon hydroxylase (AHH) activity was measured in the breast tumours of 153 primary and 17 recurrent cancer patients, and in 18 patients with benign breast tumour. All operations were carried out in 1983-84. The cytosolic fraction was collected for steroid receptor determination, and microsomes were separated for AHH assay from the same tissue samples. The AHH distribution was wide and highly skewed in all groups. About 10% of the samples showed activities below detection limit. The medians and ranges for primary cancers were 34 (less than 5-2683), for recurrent cancers 40 (20-239) and for benign tumours 11 (less than 5-37) fmol min-1 mg-1 protein. After logarithmic transformation, the mean AHH activities of cancer samples differed significantly from those of benign tumours. The logarithm of AHH activity (log AHH) correlates positively with axillary lymph node status, and negatively with steroid receptor levels. The development of the disease and the survival of the patients were followed for 4 years. The survival and the disease-free interval of the cancer patients who had low AHH activity was significantly higher than that of the high AHH group. The multivariate analysis with Cox's proportional hazad model showed primary tumour size, progesterone receptor concentration, nodal status and log AHH to be the most important independent prognostic factors for survival, while the occurrence of metastases, log AHH and tumour size were the equivalent factors for the disease-free interval in primary breast cancers. We conclude that AHH activity may reflect the overall malignant potential of breast cancer tissue.

The relationship between debrisoquine oxidation phenotype and the pharmacokinetics of chlorpropamide.

The pharmacokinetics and urinary metabolite pattern of a single oral dose of chlorpropamide 250 mg have been studied in 6 extensive and 5 poor metabolizers of debrisoquine. Ammonium chloride was given orally to acidify the urine in order to make elimination of the parent drug dependent on metabolism alone. The concentration profile in serum and the pharmacokinetic parameters of the parent drug were similar in both groups. However, the ratio in urine of unchanged chlorpropamide to its hydroxylated metabolites was higher in poor than in extensive metabolizers.