Interaction of ethanol and glipizide in humans

The hypoglycemic effect of 2.5 mg glipizide and the potentiation of this effect by ethanol were studied in 10 normal-weight nondiabetic subjects. The reductions in blood glucose concentrations were similar in time of onset and extent (2 mM) whether glipizide was taken alone or in combination with ethanol. However, the return of blood glucose toward fasting level was delayed by ethanol. Beta-Cell secretory activity, evaluated from the concentrations of insulin and C-peptide, was unchanged by ethanol. The serum glipizide concentrations were reproducible within subjects, whereas there was a considerable interindividual variation. This heterogeneity in the rise in glipizide concentration was strongly correlated with blood glucose fall and insulin secretion. Thus, ethanol can prolong but does not augment the hypoglycemia induced by glipizide. The heterogeneity in glipizide concentration seems to be caused by an interindividual variation in kinetics.

Different effects of glyburide and glipizide on insulin secretion and hepatic glucose production in normal and NIDDM subjects

Glyburide (GB) and glipizide (GZ) differ in their pharmacokinetics, but it is not known whether they also differ in mode of action. To examine this question, 10 young healthy subjects and 6 non-insulin-dependent diabetic (NIDDM) patients participated in each of three studies: 1) infusion of saline for 120 min followed by a 100-min hyperglycemic (125 mg/dl) clamp; 2) 120-min primed continuous infusion of GZ followed by a 100-min hyperglycemic clamp; and 3) 120-min primed continuous infusion of GB followed by a 100-min hyperglycemic clamp. The GB and GZ infusions were continued throughout the hyperglycemic clamp. Similar plasma concentrations of GB and GZ were obtained in both groups. All studies were performed with [3-3H]glucose to allow quantification of hepatic glucose production. When administered under basal conditions of glycemia, the acute phase (0-10 min) of plasma insulin and C-peptide increase in both control and NIDDM subjects was twice as great with GZ compared with GB (P less than .01). During the hyperglycemic-clamp studies performed in normal subjects, both GB and GZ increased the first- (1.6-fold) and second- (2.2-fold) phase plasma insulin responses more than hyperglycemia alone. During the hyperglycemic clamp in NIDDM subjects, the first-phase plasma insulin response was absent, and the second-phase insulin response was markedly impaired. Neither GB nor GZ improved first-phase insulin secretion in the NIDDM patients. In both NIDDM and control subjects, the effects of hyperglycemia and sulfonylurea drugs (both GB and GZ) on the first- and second-phase plasma insulin responses were simply additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of pharmacokinetics, metabolic effects and mechanisms of action of glyburide and glipizide during long-term treatment

Fourteen non-insulin-dependent diabetic (NIDDM) patients continued their previous medication (7 on glyburide, 7 on glipizide) for 6 mo, after which they switched to the alternate treatment for another 6 mo. The treatment periods were followed by 1 mo of placebo. The sulfonylurea dose was increased to achieve fasting plasma glucose levels less than 9 mM or to a total maximum daily dose of 25 mg. The mean final doses of glyburide (14.7 +/- 2.4 mg/day) and glipizide (15.2 +/- 2.2 mg/day) were similar. Postprandial (postdose) glipizide levels were higher than those of glyburide, whereas fasting (predose) glyburide concentrations were higher than those of glipizide. Both treatments improved glucose control by 25% compared with placebo. Glipizide therapy evoked higher postprandial insulin concentrations than did glyburide, whereas basal insulin concentrations were higher during glyburide. Insulin sensitivity, assessed by an insulin tolerance test, was more improved with glyburide than with glipizide. In conclusion, overall glucose control is similarly improved by glyburide and glipizide. However, glipizide amplifies the plasma insulin response to meals more than glyburide, whereas glyburide enhances basal insulin secretion more than glipizide. Both pharmacokinetic and pharmacodynamic factors may contribute to these differences.

Atrial natriuretic peptide and blood pressure in a geographically defined population

Plasma atrial natriuretic peptide (ANP) was measured in 717 subjects in a cross-sectional study of patients with hypertension (treated and untreated) and normotensive controls, representatives of a geographically defined population. ANP concentrations did not differ between the groups and there was no correlation with blood pressure. These results do not support the view that hypertensive and normotensive subjects have different ANP concentrations; they also call into question the role of ANP in the development of high blood pressure.

3,4-Dihydroxypyridine: a potential antithyroid drug

3,4-Dihydroxypyridine (3,4-DHP), a goitrogenic derivative of the plant amino acid mimosine, has no SH-group, in contrast to conventional antithyroid agents such as methimazole (MMI) and propylthiouracil (PTU). The current in vitro study shows that 3,4-DHP, like MMI and PTU, inhibits iodination of human thyroglobulin and interferes with mitogenic activation of human lymphocytes. This, together with a very low murine bone marrow toxicity, probably related to the absence of an SH-group, makes 3,4-DHP a potential antithyroid drug.

Clinical pharmacology of sulfonylureas

Sulfonylureas seem to have similar mechanisms of action, including an acceleration and increase of insulin secretion, an increase of the systemic availability of insulin, and probably indirectly, an increase of insulin action. Sulfonylureas may postpone the development of impaired glucose tolerance (IGT) to manifest non-insulin-dependent diabetes mellitus (NIDDM), and all NIDDM subjects should benefit from sulfonylurea treatment except those in whom insulin secretion has been attenuated. The most effective use is the combination of diet restriction and sulfonylurea introduced in NIDDM subjects soon after transition from IGT to NIDDM. A simple screening procedure has been devised to find the subjects at this early stage. Newer sulfonylureas, such as glipizide and glyburide, are more potent than the older ones, such as tolbutamide and chlorpropamide. During chronic treatment, glipizide and glyburide seem to be equally effective in reducing blood glucose levels, and they do so without causing a chronic elevation of insulin secretion, signifying that they do not increase the risk of pancreatic B cell exhaustion. Glipizide has rapid and complete absorption, as well as a rapid distribution and elimination. This may explain why it is less liable than other sulfonylureas to provoke long-lasting hypoglycemia, which is the major danger when using sulfonylureas. Despite its rapid elimination, 7.5 to 15 mg glipizide can be administered once daily without loss of therapeutic efficacy. This may be due in part to enterohepatic recirculation of the drug in response to meals. The therapeutic efficacy is increased if glipizide is received half an hour before breakfast.

Lack of primary effect of sulphonylurea (glipizide) on plasma lipoproteins and insulin action in former type 2 diabetics with attenuated insulin secretion

A double-blind, placebo-controlled investigation has been made into the effects of 8 weeks of glipizide treatment in diabetics previously classified as Type 2 but with subsequent attenuation of insulin secretion and thence maintained on exogenous insulin. Although all patients were exposed to therapeutic plasma concentrations of glipizide, fasting blood glucose, haemoglobin A1 and plasma lipoproteins (HDL, LDL, total cholesterol and triglycerides) did not show any consistent improvement following this treatment. It appears unlikely that SU (glipizide) has any primary effect on insulin action or on plasma lipoproteins. Its primary action is to augment insulin release and availability, so, its use should be restricted to Type 2 diabetics who retain insulin secretion.

Concomitant food intake can increase the bioavailability of propranolol by transient inhibition of its presystemic primary conjugation

The influence of concomitant food intake on the bioavailability and presystemic primary conjugation of propranolol (80 mg) was studied in 11 healthy women. Food increased the maximum serum concentration and serum AUC of propranolol (P less than 0.05) and reduced those of conjugated propranolol (P less than 0.05). The mean AUC ratio of conjugated/unchanged propranolol was 13:1 in the fasting state but only about 6:1 in the nonfasting state (P less than 0.001). The time to maximum serum concentration and the t1/2 were not affected by food. There was no influence of food on any kinetic parameter of propranolol or conjugated propranolol when a slow-release formulation was used. We conclude that concomitant food intake can evoke a short-lasting, delivery rate-dependent inhibition of the presystemic primary conjugation of propranolol. This is one, but not the sole, mechanism by which food can enhance propranolol bioavailability.

Reduction of paracetamol and aspirin metabolism during viral hepatitis

The single-dose pharmacokinetics of two analgesic drugs, paracetamol (acetaminophen) and aspirin, were studied in healthy volunteers and in patients with viral hepatitis during the acute and the convalescent phase. Impaired elimination of paracetamol and aspirin was found in hepatitis patients, while plasma peak concentrations were unaffected. Recovered patients were not different from healthy controls in the rate of drug elimination. The data suggest normal single dosage for these drugs in acute viral hepatitis, and dosage modification only in severe cases.

Therapeutic equivalence of once- and thrice-daily glipizide

Two cross-over studies were carried out in 23 patients with Type 2 diabetes, to examine whether glipizide, a potent sulphonylurea with fast and complete absorption and rapid elimination (t1/2 less than 5 h), can be given once-daily without loss of therapeutic effect. In both studies, patients were randomly assigned to an initial dose of 7.5 mg once daily or 2.5 mg three-times daily, which was increased to 15 mg o.d. or 5 mg t.i.d. if the fasting plasma glucose remained over 10 mmol/l on the lower dosage. In Study 1 (n = 11), administration once a day before breakfast was compared with intake before breakfast, lunch and early dinner (5 p.m.) and in Study 2 (n = 12) the comparison was between intake once-daily before breakfast and dosing before breakfast, lunch, and at bedtime (10 p.m.). Neither the 24-hour urinary glucose excretion nor HbA1, fasting plasma glucose, insulin or C-peptide levels differed between the once and three times daily administration with the third dose given before early dinner. The nadir plasma levels of glipizide were not significantly different and were often too low to be detected. Postponing the third dose until 10 p.m. did not produce any improvement in HbA1 or in fasting plasma glucose, insulin or C-peptide. The mean nadir glipizide levels following this schedule were twice as high as those after once-daily administration. As expected, the plasma glipizide after breakfast was higher when the whole dose was taken before breakfast than when it was divided. The corresponding plasma level of insulin was higher and that of plasma glucose was lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic interaction of acetylsalicylic acid and dipyridamole

It is often recommended that acetylsalicylic acid (ASA) and dipyridamole should be given together in order to obtain secondary prophylaxis against certain ischaemic diseases. Therefore, the possible pharmacokinetic interactions between these agents were assessed following single-dose exposures in 14 healthy volunteers. The plasma concentrations of ASA, salicylic acid (SA) and dipyridamole were measured by selective h.p.l.c. techniques. It was found that, while dipyridamole kinetics were unaffected by concurrent ASA, concurrent dipyridamole significantly enhanced the peak concentration (24%) and AUC (27%) of ASA. Thus, co-administered dipyridamole might influence the anti-platelet effect of ASA.

Pharmacokinetics and metabolic effects of glibenclamide and glipizide in type 2 diabetics

Fifteen Type 2 diabetics were treated for 4-week periods with once daily (10 mg) glibenclamide, glipizide and placebo according to a double-blind cross-over protocol. Post-dose glipizide concentrations were three times higher than those of glibenclamide, due to the incomplete bioavailability of the latter. On the other hand, pre-dose drug levels were similar, as an expression of the slower absorption and/or elimination of glibenclamide. Both active treatments reduced postprandial blood glucose concentrations and 24-hour urinary glucose excretion to a similar degree, but fasting blood glucose concentrations were slightly lower during glibenclamide treatment. Both active treatments enhanced fasting and postprandial insulin and C-peptide concentrations, the C-peptide response being greater after glipizide than after glibenclamide. Plasma glucagon and GIP concentrations were not significantly affected. Insulin sensitivity was increased by glibenclamide but not by glipizide. Neither therapy affected insulin binding to erythrocytes. It appears that both glibenclamide and glipizide improved glucose metabolism by sustained stimulation of insulin secretion, which was most pronounced with glipizide. Only glibenclamide improved insulin sensitivity and was slightly more active than glipizide on fasting blood glucose levels. The differences may be consequences of the pharmacokinetics, but differences in pharmacodynamics cannot be excluded.

Indobufen interacts with the sulphonylurea, glipizide, but not with the beta-adrenergic receptor antagonists, propranolol and atenolol

This study assessed the possible interactions of the cyclooxygenase inhibitor indobufen with one sulphonylurea, glipizide, and with two beta-adrenoceptor antagonists, one of which is extensively metabolised already in the first passage through the liver (propranolol) while the other essentially escapes biotransformation (atenolol). Indobufen was first given as a single 200 mg dose and then for a 5 day period in a dosage of 200 mg twice daily, to six healthy volunteers. Glipizide (5 mg), propranolol (80 mg) and atenolol (100 mg) were given as single doses before and during indobufen medication. The drug concentrations were measured by selective and sensitive h.p.l.c. methods. The findings suggest that the lipophilic acid indobufen can inhibit the metabolic inactivation of another lipophilic acid, glipizide, but does not interfere with the disposal of the two basic drugs, propranolol and atenolol. The increased glipizide concentrations following indobufen were associated with an enhanced blood glucose reduction. Hence, this interaction may be clinically relevant.

In vivo absorption of theophylline and salicylic acid from rat small intestine

In vivo absorption of theophylline and salicylic acid from the rat small intestine was studied by a closed segment technique. The drugs were administered at 1 and 4 mM in dissolved form, both in the presence and absence of phlorizin (0.01 mM). Drug concentrations were measured by high-pressure liquid chromatography. Phlorizin inhibited the absorption of theophylline (pKa = 8.6) at 4 mM but not at 1 mM. In contrast, the absorption of salicylic acid (pKa = 3) both at 1 and 4 mM was unaffected by phlorizin. This suggests that an active transport system, sensitive to phlorizin, is involved in the rat intestinal absorption of theophylline, but not in that of salicylic acid. Apart from differences in drug structure, differences in the degree of ionization may influence the access of acidic drugs to this transport system.

In vitro and in vivo evaluation of controlled-release and enteric-coated formulations of sodium salicylate

The bioavailability and pharmacokinetics of salicylic acid (SA) were studied after single and multiple doses of a new slow-release formulation, based on porous membrane diffusion of sodium salicylate (NaSA). A solution of NaSA and an enteric-coated tablet of NaSA were used for comparison. Dissolution rate studies were carried out at various pH values, and both solid formulations showed pH-dependent release rates. The enteric-coated tablet released its content rapidly at intestinal pH but slowly and irregularly at gastric pH. The dissolution from the controlled-release formulation at intestinal pH was completed after 6h and the drug was delivered at a constant rate. At gastric pH the release rate was lower but complete release was obtained within 24h. The novel formulation appeared to offer complete bioavailability of SA and an even and sustained release of SA, allowing twice-daily medication without increased fluctuations in SA concentrations.

Local anaesthesia and immunomodulatory effects of antithyroid drugs

Propylthiouracil (PTU) and propranolol can suppress, while methimazole (MMI) can enhance, mitogenic activation of lymphocytes. The present study investigated whether this effect of PTU, as has been shown for propranolol, relates to local anaesthetic activity. MMI (1 mM) but not PTU (1 mM) reduced the action potential in rat skeletal muscle. Thus, PTU seems to lack local anaesthetic activity. Moreover, the recorded local anaesthetic capacity of MMI hardly explains the stimulatory influence of MMI on lymphocyte activation. Apparently, the interference of MMI and PTU with lymphocyte activation seems to be due to another mechanism than local anaesthetic activity.

Influence of cigarette smoking on goiter formation, thyroglobulin, and thyroid hormone levels in women

The possible influence of cigarette smoking on goiter formation, thyroglobulin (Tg) secretion, and thyroid hormone production was assessed by estimations of the presence of palpable goiter and by RIAs of Tg, T3, rT3, T4, and TSH in sera from 441 women (48-53 yr old), representing a normal population included in a study on the prevalence of thyroid disease. Smoking habits were evaluated by a questionnaire, and the women were then classified as never smokers (n = 192), smokers (n = 169), and exsmokers (n = 80). Smokers were subdivided as moderate (1-19 cigarettes/day) and heavy (greater than or equal to 20 cigarettes/day). Palpable goiter was found in 15% of the smokers, in contrast to only 4% of the exsmokers and 9% of the never smokers. Among smokers, 37% had serum Tg values over 30 micrograms/liter (third quartile), while such values were found in only 16% of the exsmokers and 18% of the never smokers. In addition, smokers were found to have higher serum T3 and lower rT3 concentrations than never smokers; this difference was most pronounced in heavy smokers. Serum T4 was not different, while TSH was insignificantly lower in smokers than in nonsmokers. Exsmokers did not differ significantly from never smokers in any of these parameters. It seems possible that cigarette smoking may have two, calorigenically opposed, effects on thyroid hormone production; it may be goitrogenic (possibly due to inhaled thiocyanate), but it may also enhance the formation of T3 at the expense of rT3 formation.

Actions and interactions of acetylsalicylic acid, salicylic acid and diflunisal on platelet aggregation

Acetylsalicylic acid (ASA) is increasingly employed in the secondary prophylaxis of thromboembolic diseases, due to its capacity to inhibit platelet aggregation. The anti-aggregatory effect of ASA on platelets can be inhibited in vitro by a high concentration of salicylic acid (SA). SA is generated in vivo upon ASA administration, and the SA thus formed might impair the antiplatelet effect of ASA. To assess this possibility, the platelet response to ASA was tested in healthy volunteers before and after medication for 1 week with ASA 1 g t.i.d., with SA 1 g t.i.d., and with the SA derivative diflunisal 0.5 g b.i.d. Pre-medication test doses of 1 g ASA always inhibited platelet aggregation in vivo. Neither treatment with SA nor diflunisal, producing plasma steady-state concentrations of about 1.0 and 0.35 mmol/l, respectively, inhibited platelet aggregation. Nor did administration of SA, diflunisal or ASA itself impair the anti-aggregatory effect of a fresh test dose of ASA. ASA inhibited platelet aggregation in vitro at 0.03 mmol/l, whereas SA and diflunisal failed to impair platelet aggregation until concentrations exceeding 2.0 and 0.5 mmol/l, respectively, were reached. These findings make it unlikely that SA formed upon administration of ASA would impair the anti-aggregating capacity of ASA.

Vasoactive intestinal peptide stimulation of human thyroid cell function

Neurons containing vasoactive intestinal peptide (VIP) have been found to reach thyroid follicular cells in man and other mammals. Human thyroid cells in culture were exposed to different concentrations of VIP and TSH, and thyroid cell activation was assessed by measurements of cAMP accumulation. VIP exerted a dose-dependent activation, and this thyroid-stimulating effect was more rapid and short-acting than that of TSH. At low concentrations of the two agents, their effects were additive, but they seemed to initiate their effects via different receptors, since polyphloretin phosphate inhibited the effect of TSH but not that of VIP. Moreover, antiadrenergic and anticholinergic agents did not influence thyroid activation by VIP. In addition to cAMP activation in cell cultures, VIP stimulated T4 release from human thyroid slices. It is possible that, in addition to sympathetic-adrenergic and parasympathetic-cholinergic nerves, VIPergic nerves may participate in the autonomic nervous control of thyroid function.

Fetal heart rate during treatment of maternal hypertension with beta-adrenergic antagonists. A preliminary report

The effects of two different beta-adrenergic antagonists on maternal arterial pressure and fetal heart rate were studied in 8 pregnant women with pregnancy hypertension. The fetal heart rate was monitored by abdominal ECG recording under standardized conditions. Basal heart rate, long-term variability and short-term variability were calculated in a computer. Four patients received 50-100 mg atenolol once daily; the other 4 received pindolol 10 mg b.i.d. Reduction in mean arterial blood pressure was seen in both groups of patients. The basal fetal heart rate was decreased in atenolol-exposed fetuses but not in pindolol-exposed fetuses. In this preliminary study there was no apparent effect on the fetal heart rate variability.

Drug selection in the treatment of pregnancy hypertension. A survey

Effective blood pressure treatment has only been available during the last 20-25 years. Most antihypertensive drugs employed for other hypertensive conditions have also been used in hypertensive states of pregnancy. In this survey, most of the drugs already in use and some new ones are discussed. No special emphasis is placed on the use of drugs in emergency situations. As beta-adrenoceptor blocking drugs are widely used nowadays, the principal differences between some beta-blockers are discussed in detail. A discussion of future requirements in order to get a better picture of the value of antihypertensive drugs completes this survey.

Chlorpropamide-alcohol flush: significance of body weight, sex and serum chlorpropamide level

Chlorpropamide-alcohol flush (CPAF) tests were carried out in 15 male and 15 female Type 2 diabetics. Twelve subjects were CPAF-positive and 18 were -negative. The two groups did not differ in age or duration of diabetes, but the CPAF-positive subjects weighed less (mean difference 13 kg) and had higher plasma chlorpropamide levels. There was a negative correlation between plasma chlorpropamide and body weight, and a positive correlation between plasma chlorpropamide and the increase in facial skin temperature. Females had higher plasma chlorpropamide, a greater skin temperature increase and lower body weight than males; there were 11 females and only 1 male amongst the 12 CPAF-positive subjects. The findings confirm that plasma chlorpropamide is a major determinant of the CPAF reaction and also show that body weight strongly influences the chlorpropamide level and, consequently, the outcome of the CPAF test. The sex difference in body weight probably accounts for most, if not all, of the sex difference in the incidence of the CPAF.