Effect of linagliptin on the pharmacokinetics and pharmacodynamics of warfarin in healthy volunteers.

OBJECTIVE: To investigate the effect of the estimated highest therapeutic dose of linagliptin (5 mg) on the pharmacokinetics and pharmacodynamics of warfarin, a CYP2C9 substrate. SUBJECTS AND METHODS: This open-label, 2-period, fixed-sequence trial enrolled 18 healthy male volunteers, 17 of whom were homozygous for CYP2C9*1/*1. Subjects received a single oral dose of warfarin (10 mg) followed by a washout period of at least 14 days. Subjects then received oral linagliptin 5 mg once daily for 12 days (i.e. steady state) with a single dose of warfarin (10 mg) on Day 6. R(+) warfarin, S(-) warfarin, prothrombin time (PT) and international normalized ratio (INR) were assayed pre-dose and up to 168 h post-dose. RESULTS: The geometric mean ratios (GMRs) (90% confidence interval (CI)) of AUC0-∞ and Cmax for (linagliptin + warfarin)/warfarin were 98.5 (95.7 - 101.5) and 99.7 (94.7 - 104.9), respectively, for R-warfarin; 103.0 (99.1 - 107.0) and 100.9 (93.7 - 108.6), respectively, for S-warfarin. Concomitant administration of linagliptin and warfarin had o clinically relevant effect on the AUC0-168 for INR or PT. The GMRs (90% CI) of INR nd PT AUC0-168 for (linagliptin + warfarin)/ warfarin were 93.4 (86.2 - 101.1) and 103.2 (95.4 - 111.6), respectively. The corresponding Eax values for both INR and PT were slightly increased after co-administration of linagliptin and warfarin compared with warfarin alone, being 104.3 (85.2 - 127.6) and 15.1 (94.3 -140.6), respectively, reflecting the higher variability of these endpoints. Co-administration of linagliptin and warfarin was well tolerated. CONCLUSIONS: Coadministration of linagliptin did not alter the pharmacokinetics or pharmacodynamics of R- or S-warfarin, indicating that no dosage adjustment for warfarin is necessary when co-administered with linagliptin.

A new oral direct thrombin inhibitor, dabigatran etexilate, compared with enoxaparin for prevention of thromboembolic events following total hip or knee replacement: the BISTRO II randomized trial.

BACKGROUND: Dabigatran etexilate is an oral direct thrombin inhibitor undergoing evaluation for the prevention of venous thromboembolism (VTE) following orthopedic surgery. METHODS: In a multicenter, parallel-group, double-blind study, 1973 patients undergoing total hip or knee replacement were randomized to 6-10 days of oral dabigatran etexilate (50, 150 mg twice daily, 300 mg once daily, 225 mg twice daily), starting 1-4 h after surgery, or subcutaneous enoxaparin (40 mg once daily) starting 12 h prior to surgery. The primary efficacy outcome was the incidence of VTE (detected by bilateral venography or symptomatic events) during treatment. RESULTS: Of the 1949 treated patients, 1464 (75%) patients were evaluable for the efficacy analysis. VTE occurred in 28.5%, 17.4%, 16.6%, 13.1% and 24% of patients assigned to dabigatran etexilate 50, 150 mg twice daily, 300 mg once daily, 225 mg twice daily and enoxaparin, respectively. A significant dose-dependent decrease in VTE occurred with increasing doses of dabigatran etexilate (P < 0.0001). Compared with enoxaparin, VTE was significantly lower in patients receiving 150 mg twice daily [odds ratio (OR) 0.65, P = 0.04], 300 mg once daily (OR 0.61, P = 0.02) and 225 mg twice daily (OR 0.47, P = 0.0007). Compared with enoxaparin, major bleeding was significantly lower with 50 mg twice daily (0.3% vs. 2.0%, P = 0.047) but elevated with higher doses, nearly reaching statistical significance with the 300 mg once-daily dose (4.7%, P = 0.051). CONCLUSIONS: Oral administration of dabigatran etexilate, commenced early in the postoperative period, was effective and safe across a range of doses. Further optimization of the efficacy/safety balance will be addressed in future studies.

Dose escalating safety study of a new oral direct thrombin inhibitor, dabigatran etexilate, in patients undergoing total hip replacement: BISTRO I.

BACKGROUND: Dabigatran etexilate (BIBR 1048) is an oral direct thrombin inhibitor undergoing evaluation for the prevention of venous thromboembolism (VTE) following total hip replacement. Following oral administration, dabigatran etexilate is rapidly converted to its active form dabigatran (BIBR 953 ZW). OBJECTIVES: To determine the safe therapeutic range of dabigatran etexilate following total hip replacement. METHODS: In a multicenter, open-label, dose-escalating study, 314 patients received oral doses of dabigatran etexilate (12.5, 25, 50, 100, 150, 200 and 300 mg twice daily or 150 and 300 mg once daily) administered 4-8 h after surgery, for 6-10 days. Dose escalation was based on clinical and pharmacokinetic data. The primary safety outcome was major bleeding. The primary efficacy outcome included venographic deep vein thrombosis (DVT), symptomatic DVT and pulmonary embolism, during the treatment period. RESULTS: No major bleeding event was observed in any group, but two patients at the highest dose (300 mg twice daily) suffered bleeding from multiple sites associated with reduced renal clearance and prolonged pharmacodynamic (PD) parameters. A dose-response was demonstrated for minor bleeding events. Of the 289 treated patients, 225 patients had evaluable venograms. The overall incidence of DVT was 12.4% (28/225 patients). There was no consistent relationship between the dose and incidence of DVT, the highest incidence in any group being 20.8% (5/24 patients). The lowest dose (12.5 mg twice daily) showed a high rate of proximal DVT [12.5% (3/24)] and no increase in PD parameters. Peak and trough plasma concentrations, area under the dabigatran plasma concentration-time curve and PD parameters also increased in proportion with the dose. Higher dabigatran plasma concentrations were associated with lower DVT rates. Approximately 20% of the patients had low plasma concentrations after the first dose suggesting further optimization of the preliminary tablet formulation is required. CONCLUSIONS: Dabigatran etexilate demonstrates an acceptable safety profile, with a therapeutic window above 12.5 mg and below 300 mg twice daily. The low number of VTE events within each treatment group indicates a satisfactory antithrombotic potential, although the study was not powered for an efficacy analysis. Additional studies are ongoing to optimize oral absorption and the efficacy/safety balance.

Inhibitory effect of telmisartan on the blood pressure response to angiotensin II challenge.

Telmisartan is a new angiotensin receptor antagonist possessing potent, selective, and insurmountable inhibitory activity specific to the angiotensin II type 1 (AT 1 ) receptor. The current study was performed to determine the inhibition of the angiotensin II pressor response by telmisartan in 48 healthy volunteers challenged with hypertension-inducing doses of i.v. angiotensin II. Subjects were challenged with this dose of angiotensin II at intervals between 0.25 and 48 h after double-blind single-dose oral administration of telmisartan 20 mg (n = 12), 40 mg (n = 12), or 80 mg (n = 12) or placebo (n = 12) in parallel groups. Diastolic and systolic blood pressure and pulse rate were recorded continuously using a servophotoplethysmograph. Urine samples were collected during the study for urinalysis. Tolerability of telmisartan, in comparison with placebo, was also monitored throughout the study. Telmisartan 20-80 mg dose dependently inhibited the increase in diastolic and systolic blood pressure induced by angiotensin II. Telmisartan 40 mg produced 80.1% maximum inhibition, and with 80 mg 89.6% maximum inhibition of diastolic blood pressure was achieved. Inhibition was apparent after 0.3-1.1 h and was still observed 48 h after administration for all telmisartan doses. The inhibitory effect of telmisartan 20, 40, and 80 mg, 48 h after dosing was significantly greater than that of placebo. A > 25% inhibition of the angiotensin II response on diastolic blood pressure was detected until 26.9, 35.4, and 40.5 h, respectively, after telmisartan 20 mg, 40 mg, and 80 mg. Anti-clockwise hysteresis was observed, indicating a delay and longer persistence of effect than to be expected from the plasma concentration-time course. The slow dissociation of telmisartan from the receptor probably contributed to this hysteresis. The incidence of adverse events was comparable in telmisartan-and placebo-treated subjects and was not dose dependent. In conclusion, telmisartan 40 mg provides rapid-onset, well-tolerated, and near-maximal inhibition of angiotensin II-induced hypertension, with maintenance of the inhibitory effect for 48 h.

AT1 receptor antagonist telmisartan administered peripherally inhibits central responses to angiotensin II in conscious rats.

The effects of systemic treatment with the AT1 receptor antagonist telmisartan on central effects of angiotensin II (Ang II), namely, increase in blood pressure, vasopressin release into the circulation, and drinking response, were investigated in conscious, normotensive rats. The central responses to i.c.v. Ang II (30 ng/kg) were measured at 0.5, 2, 4, and 24 h following acute i.v. or acute and chronic oral telmisartan application. At a dose of 10 mg/kg i.v., the drinking response to i.c.v. Ang II was completely blocked over 4 h, while the pressor response and the release of vasopressin in response to i.c.v. Ang II were blocked by 60 to 80%. The inhibition of the centrally mediated pressor and drinking response to Ang II was sustained over 24 h. The lower doses of telmisartan (0.3 and 1 mg/kg) significantly inhibited the Ang II-induced actions over 4 h. A consistent 24-h inhibition of the central responses to i.c.v. Ang II was obtained after acute and chronic oral treatment with 30 mg/kg telmisartan. Oral treatment with 1 and 3 mg/kg telmisartan produced a slight but inconsistent inhibition of the central actions of Ang II. Telmisartan concentrations measured in the cerebrospinal fluid following 8 days of consecutive daily oral treatment (1-30 mg/kg) ranged from 0.87 +/- 0.27 ng/ml (1 mg/kg/day) to 46.5 +/- 11.6 ng/ml (30 mg/kg/day). Our results demonstrate that, following peripheral administration, the AT1 receptor antagonist telmisartan can penetrate the blood-brain barrier in a dose- and time-dependent manner to inhibit centrally mediated effects of Ang II.

Pharmacokinetics of orally and intravenously administered telmisartan in healthy young and elderly volunteers and in hypertensive patients.

A series of studies was conducted in healthy young males and healthy elderly males or females to evaluate the pharmacokinetic profile of telmisartan. In addition, two phase-II clinical trials assessed the pharmacokinetics and the safety of telmisartan in mild-to-moderate hypertensive patients. Telmisartan was given as a single oral (1-160 mg) or intravenous (10-160 mg) dose to young males. In another multiple-dose study, telmisartan 320 mg was administered orally once daily for 7 days to healthy young male subjects. Elderly subjects received oral telmisartan (20 and 120 mg) once daily for 7 days. Telmisartan doses of 10, 20, 40, 80, 120 and 160 mg were taken once daily by mild-to-moderate hypertensive patients for 7 days. Additionally, oral telmisartan (40, 80 or 120 mg) was administered once daily for 28 days to hypertensive subjects. Following oral dosing, median time to maximum plasma telmisartan concentration was 0.5 - 2 h, with maximum plasma concentrations increasing disproportionately with dose. By contrast, plasma concentrations were directly related to the intravenous dose. Steady state was observed after 5-7 days of once-daily administration, and there was no clinically relevant accumulation at 28 days. The plasma concentration-time profiles were similar in all study groups and were characterized by fast absorption and a rapid biexponential decline after the peak plasma concentration, with a prolonged terminal elimination phase (> 20 h in healthy and hypertensive subjects). Telmisartan was well tolerated, with a low incidence of drug-related adverse events. The most frequent event was headache, which also occurred in placebo-treated control subjects. No changes in heart rate, electrocardiograms or clinical chemistry were detected following receipt of telmisartan. The study thus shows that high systemic levels of telmisartan, which are well tolerated, can be attained in healthy adults of any age and in hypertensive subjects. The long terminal elimination half-life makes telmisartan suitable for once-daily dosing and contributes to the sustained efficacy over the full 24-h dosing interval.

Multiple-dose pharmacokinetics of telmisartan and of hydrochlorothiazide following concurrent administration in healthy subjects.

This open-label, crossover study had two objectives: to compare the steady-state pharmacokinetics of high-dose telmisartan with and without coadministered high-dose hydrochlorothiazide and to compare the steady-state pharmacokinetics of hydrochlorothiazide with and without coadministered telmisartan. A total of 13 healthy males and females of nonchildbearing potential received the following oral, once-daily medications, each for 7 days: telmisartan 160 mg, hydrochlorothiazide 25 mg, and telmisartan 160 mg plus hydrochlorothiazide 25 mg. Between medication periods, there was a 14-day washout. Blood was collected at intervals over 48 and 84 hours, respectively, at the end of the 7-day dosing period for the determination of plasma telmisartan and hydrochlorothiazide concentrations by high-performance liquid chromatography. Predose blood samples were also collected on days 1, 6, and 7. Tolerability of single-agent and combination medication was monitored. For hydrochlorothiazide and telmisartan, given alone or in combination, there were no appreciable differences in trough plasma concentrations between days 6, 7, and 8; thus, at day 7, both agents had achieved steady state. Mean values of the primary end points (Cmax and AUC0-24) and secondary end points (Cmin and t1/2) for both telmisartan and hyrochlorothiazide were unaffected when administered simultaneously. Moreover, concurrent telmisartan had no effect on urinary excretion of hydrochlorothiazide. Transient lightheadedness, associated with postural hypotension, was the most common adverse event. The absence of any significant effects on the pharmacokinetics of either hydrochlorothiazide or telmisartan shows that no dose adjustment is required if the two agents are given concurrently for the management of hypertension.

Absorption, metabolism, and excretion of intravenously and orally administered [14C]telmisartan in healthy volunteers.

The study was conducted in healthy male volunteers to evaluate the absorption, metabolic pattern, and mode of elimination of telmisartan, a nonpeptide angiotensin II receptor antagonist. [14C]telmisartan was administered orally in solution as a single 40 mg dose to 5 subjects. A further 5 subjects received short-term intravenous infusion of [14C]telmisartan 40 mg. Measurement of total 14C radioactivity in plasma showed that about 50% was absorbed following oral administration, with maximum plasma concentration observed after 0.5 to 1 hour. Absolute bioavailability was 43%. On average, 84% of total radioactivity in plasma reflected the parent compound. The remainder of total radioactivity could be ascribed to the glucuronide conjugate of telmisartan, which represented the only metabolite in man. About 99.5% of telmisartan was bound to plasma protein, mainly to albumin and alpha-1-acid glycoprotein. Telmisartan was reversibly distributed into erythrocytes. More than 90% of administered dose was excreted within 120 hours, and the excretion balance was complete 144 hours after dosing. Radioactivity was almost exclusively (> 98%) excreted via the feces; urinary excretion accounted for < 1% of the dose, irrespective of the route of administration. In the small fraction excreted into urine, the glucuronide conjugate of telmisartan was predominant. Although some telmisartan glucuronide was detected in plasma, only unchanged drug was identified in the feces. No changes in vital signs, electrocardiogram, or clinical laboratory tests were detected following telmisartan administration, and adverse events, predominantly unrelated to treatment and of mild intensity, were infrequent. One subject fainted and, on another occasion, reported faintness; these events were probably due to the antihypertensive action of the intravenous study medication.

Steady-state pharmacodynamics and pharmacokinetics of warfarin in the presence and absence of telmisartan in healthy male volunteers.

The effects of multiple-dose telmisartan on the steady-state pharmacodynamics and pharmacokinetics of warfarin were assessed in 12 healthy young males in an open-label, single-period study conducted over 30 days. Subjects received loading doses of oral once-daily warfarin on days 1 to 5, which were individually adjusted at days 6 and/or 9 to attain stable predose prothrombin time values (INRpre) of between 1.2 and 1.8 by the end of medication phase 1 (day 14). From days 15 to 24 (medication phase 2), subjects received oral once-daily telmisartan 120 mg in addition to individualized oral doses of once-daily warfarin. On days 25 to 31 (medication phase 3), oral once-daily warfarin was again administered alone at individualized doses. Under steady-state conditions, INRpre remained unchanged during medication phases 1, 2, and 3. The difference between phases 1 and 3 was -0.04 (95% confidence interval [CI]: -0.7 to 0.10) and between phases 2 and 1 was 0.03 (95% CI: -0.11 to 0.10). Mean trough plasma warfarin concentrations (Cpre) were stable during medication with warfarin alone but showed a small, although statistically significant, decrease during the combined-medication phase. The point estimate of the ratio of phase 2/phase 1 was 0.89 (95% CI: 0.84 to 0.95). The decrease in Cpre did not result in decreased anticoagulation. This suggests that the extent of pharmacokinetic interaction between telmisartan and warfarin is limited, and since telmisartan had no effect on INRpre and the concomitant medication was well tolerated, there is no evidence for a clinically relevant interaction between telmisartan and warfarin.

Pharmacokinetics of acetaminophen and ibuprofen when coadministered with telmisartan in healthy volunteers.

Two open-label, two-way, crossover studies were performed to assess any pharmacokinetic interaction of telmisartan with either acetaminophen or ibuprofen. Healthy male adult volunteers (n = 12) received a single oral dose of acetaminophen 1 g alone and with oral telmisartan 120 mg in one study. Oral ibuprofen 400 mg three times daily with and without oral once-daily telmisartan 120 mg was given for 7 days in the other study conducted in 6 males and 6 females. In both studies, there was a washout period of > or = 13 days between single and combination medication administration. The primary end points Cmax and AUC were compared between combination (acetaminophen or ibuprofen + telmisartan) and single-agent medication (acetaminophen or ibuprofen). Pharmacokinetic drug interaction was assessed by analysis of variance (ANOVA) and calculation of 90% confidence intervals (CI) for treatment ratios using log-transformed parameters. Bioequivalence (i.e., lack of interaction) was concluded if the 90% CI of the ratios for both Cmax and AUC were within the acceptance limit of 0.80 to 1.25. Geometric mean Cmax values for acetaminophen and R-(-)- and S-(+)-ibuprofen enantiomers were similar with and without telmisartan coadministration (12.6 micrograms/mL vs. 14.1 micrograms/mL; 17.3 micrograms/mL vs. 16.7 micrograms/mL; 19.4 micrograms/mL vs. 19.5 micrograms/mL, respectively), and values for R-(-)- as well as S-(+)-ibuprofen were bioequivalent. Geometric mean AUC values for acetaminophen and R-(-)- and S-(+)-ibuprofen were also bioequivalent with and without telmisartan. The distribution and elimination parameters of both acetaminophen and ibuprofen were comparable in the presence or absence of telmisartan. The concomitant and single-agent medications were all well tolerated. In conclusion, the long half-life and excellent safety profile of telmisartan were unaffected by concurrent acetaminophen or ibuprofen medication; thus, once-daily dosing of telmisartan can be maintained, which may help to optimize patient compliance, and patients may self-administer concomitant acetaminophen or ibuprofen.

Pharmacokinetics of repeated oral doses of amlodipine and amlodipine plus telmisartan in healthy volunteers.

This open-label, crossover study was performed to establish if there is evidence for interaction between telmisartan, an angiotensin II antagonist, and amlodipine, a class II (dihydropyridine) calcium channel antagonist, on the basis of pharmacokinetics and safety. In a two-way crossover trial, 12 healthy Caucasian males were randomized to receive once daily for 9 days oral amlodipine 10 mg with or without oral telmisartan 120 mg. After a washout period of > or = 13 days, the subjects were switched to the other medication regimen. The geometric means of the primary pharmacokinetic parameters at steady state (day 9) for amlodipine when given alone were the following: maximum plasma concentration (Cmax) 17.7 ng/mL, area under the plasma concentration-time curve (AUC) 331 ng.h/mL, and renal clearance 39.5 mL/min, with 8% of the total amlodipine dose being excreted. When concomitant telmisartan was given, the respective values were 18.7 ng/mL, 352 ng.h/mL, and 43.0 mL/min, with 9.4% of the total amlodipine dose being excreted renally. The limits of the 90% confidence intervals (CIs) for the ratios of these steady-state parameters were 0.97 to 1.14 for Cmax and 0.98 to 1.16 for AUC; both were within the predefined reference range (0.8 to 1.25) for bioequivalence. The high intersubject variability in urinary amlodipine excretion resulted in bioequivalence not being demonstrated for renal clearance. Adverse effects were few, mild to moderate in intensity, and transient whether amlodipine was given alone or with telmisartan. Vital signs, except for blood pressure, and clinical laboratory values were unaffected by either medication. The findings of this study show that concomitant telmisartan and amlodipine may be administered as there is no clinically significant variation in primary pharmacokinetic parameters of amlodipine in the presence of telmisartan, and the safety of the combination is comparable to that of amlodipine alone.

Pharmacokinetics and safety of intravenous and oral telmisartan 20 mg and 120 mg in subjects with hepatic impairment compared with healthy volunteers.

The pharmacokinetics and safety of telmisartan were assessed in subjects with hepatic impairment in a single-center, open-label study. Single oral doses of telmisartan 20 mg and 120 mg, separated by a washout period of 14 days, were given to 12 hepatically impaired subjects and 12 healthy subjects. In 5 hepatically impaired subjects who received both oral doses, a single i.v. infusion of telmisartan 120 mg was later administered. After oral dosing, the pharmacokinetic profile of telmisartan was characterized by rapid absorption and disposition kinetics and a slow terminal elimination phase with mean half-lives of 27 to 42 hours. The maximum plasma concentration and area under the telmisartan plasma concentration-time curve (AUC0-infinity) increased in hepatically impaired subjects compared with healthy volunteers 6.4-fold and 2.7-fold, respectively, for telmisartan 20 mg and 3.2-fold and 3.1-fold, respectively, for telmisartan 120 mg. Maximum plasma concentrations and AUC0-infinity after i.v. infusion were markedly elevated compared with values obtained from other studies conducted in healthy volunteers. Hepatic impairment resulted in an apparent increase in the absolute bioavailability of telmisartan, and total clearance following oral and i.v. administration was significantly reduced compared with healthy volunteers. Plasma protein binding of telmisartan was > or = 99.5% in hepatically impaired and healthy subjects and was not changed when compared to healthy subjects. Oral and i.v. telmisartan were well tolerated in both the hepatically impaired and the healthy; headache was the most common potentially telmisartan-related adverse event. Changes in vital signs and clinical laboratory parameters were transient and of no clinical relevance. The good tolerability of telmisartan in hepatically impaired patients demonstrated in this study, the proven sustained blood pressure control in hypertensive patients, and the increased exposure in patients with hepatic dysfunction suggest that effective treatment of hypertensive patients with impaired hepatic function would be achieved even with the lowest dose of telmisartan available. The increased bioavailability of telmisartan suggests that lower doses of telmisartan should be considered when the drug is administered to patients with hepatic impairment.

Pharmacokinetics of single-dose telmisartan 120 mg given during and between hemodialysis in subjects with severe renal insufficiency: comparison with healthy volunteers.

The pharmacokinetics of oral telmisartan 120 mg evaluated in subjects with severe renal insufficiency between dialyses and during hemodialysis were compared with those observed in healthy male subjects. Between dialyses and during dialysis, the plasma concentration-time curves of subjects with renal insufficiency were lower than those of healthy subjects. The mean plasma protein binding of telmisartan was 99.5% in healthy subjects, compared with mean values of 99.1% between dialyses and 98.8% during dialysis. Only very small amounts of telmisartan were removed by dialysis. Single doses of telmisartan 120 mg were well tolerated in subjects with severe renal insufficiency when administered either between dialyses or during dialysis, and no clinically relevant changes in vital signs were detected. In conclusion, the maximum plasma concentrations of telmisartan and areas under the plasma concentration-time curves in subjects with severe renal insufficiency were markedly reduced compared with healthy subjects. The fraction of telmisartan not bound to plasma proteins was increased approximately twofold. Changes in the pharmacokinetic profile in subjects with renal insufficiency did not affect the safety profile of telmisartan, which was well tolerated in these subjects.

The effect of telmisartan on the steady-state pharmacokinetics of digoxin in healthy male volunteers.

A multiple-dose, open-label, two-period, crossover randomized study was conducted in 12 healthy male volunteers to investigate the effect of multiple-dose telmisartan on the steady-state pharmacokinetics of digoxin. On day 1 of a 7-day medication period, subjects received a loading dose of digoxin 0.5 mg in the morning, followed by an evening dose of digoxin 0.25 mg, either alone or together with telmisartan 120 mg administered in the morning. On the subsequent 6 days, either digoxin 0.25 mg or digoxin 0.25 mg together with telmisartan 120 mg was administered once daily in the morning. Each 7-day medication period was separated by a washout period of > or = 14 days. A steady-state plasma concentration-time profile was assessed for digoxin during each period and for telmisartan during the period with the combined treatment. Multiple-dose telmisartan administered with digoxin resulted in higher serum digoxin concentrations than those observed after digoxin given alone. Geometric mean AUC144-168, Cmax, and Cmin values for digoxin when given in combination with telmisartan were higher by 22%, 50%, and 13%, respectively, compared with values when given alone. However, the 90% confidence interval for the geometric mean of Cmin was within the predefined 80% to 125% range of no interaction. During combination medication, digoxin tmax was shorter and Cmax/AUC144-168 increased, suggesting that the rise in digoxin Cmax may be due to more rapid drug absorption. Study medications were well tolerated, with the incidence, nature, and intensity of adverse events being similar during both medication periods. Also, no changes in vital signs or clinical laboratory tests were observed during the study. Although there was some evidence for a pharmacokinetic interaction between digoxin and telmisartan found in this study, the safety and tolerability of digoxin were unaffected by concurrent administration of telmisartan in the study population. Since any symptoms of overdose are related only to steady state and not peak concentrations and due to the fact that there was a lack of effect on serum trough levels of digoxin in this study, it is unlikely that the findings have any clinical relevance. The magnitude of increase in digoxin concentrations is comparable with increases observed with administration of calcium antagonists, carvedilol, ACE inhibitors such as captopril, and antiarrhythmic drugs such as amiodarone, quinidine, and propafenone. Monitoring of serum digoxin concentrations should be considered when patients first receive telmisartan and in the event of any changes in telmisartan dose.

Orcokinin: a novel myotropic peptide from the nervous system of the crayfish, Orconectes limosus.

A myotropic peptide, named orcokinin, was isolated from approximately 1200 abdominal nerve cords of the crayfish, Orconectes limosus. Its amino acid sequence was determined as follows: Asn-Phe-Asp-Glu-Ile-Asp-Arg-Ser-Gly-Phe-Gly-Phe-Asn. This structure was confirmed by synthesis. There is no sequence similarity to any known neuropeptide. Orcokinin exhibits high potency on the crayfish hindgut, enhancing both frequency and amplitude of spontaneous contractions. The threshold of biological activity in vitro was determined to be approximately 5 x 10(-11) M.

Testosterone-induced diminution of two peptides in spleen cells from testosterone-immunosuppressed B10 mice.

High-performance liquid chromatography (HPLC) is used to detect testosterone (T)-sensitive peptides in spleen cells isolated from female C57BL/10 mice immunosuppressed against Plasmodium chabaudi malaria by T treatment. Two peaks with retention times of about 25 min and 34 min, respectively, were identified to be diminished by about 52% and 47%, respectively, in spleen cells from T-treated mice compared to those from untreated mice. Amino acid sequencing revealed that the 24 min peak consisted of the dipeptide Met-Phe and the 34 min peak contained a degradative fragment of the alpha-chain of hemoglobin. Our data suggest that the immunosuppressive T treatment of B10 mice induces a perturbation of erythrophagocytosis in spleens.

Distribution of a novel cardioactive neuropeptide (CCAP) in the nervous system of the shore crab Carcinus maenas.

A radioimmunoassay (RIA) for the recently discovered crustacean cardioactive peptide (CCAP) has been developed and used to determine contents of CCAP in different parts of the nervous system of the shore crab Carcinus maenas. Immunoreactive material was detected throughout the nervous system. In contrast to the main ganglia which contained low levels of approximately 1.4 pmol CCAP/mg protein (brain and thoracic ganglion), a high concentration was found in a neurohemal structure, the pericardial organs (PO) (868 pmol/mg protein). A predominantly neurohormonal role of CCAP thus suggested is further supported by in vitro release studies. Incubation of POs in high (K+) saline showed that CCAP is secretable in considerable amounts by a Ca++-dependent release mechanism.

Unusual cardioactive peptide (CCAP) from pericardial organs of the shore crab Carcinus maenas.

An unusual crustacean cardioactive peptide (CCAP) from the pericardial organs of the shore crab Carcinus maenas has been purified to homogeneity by a two-step reversed-phase HPLC procedure. Manual microsequencing using the 4-(N,N-dimethylamino)azobenzene 4'-isothiocyanate/phenylisothiocyanate double-coupling technique and automated gas-phase sequencing of the oxidized peptide revealed that CCAP is a nonapeptide (M(r) 957) of the sequence Pro-Phe-[unk]Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH(2). We have confirmed the sequence by chemical synthesis of the C-terminally amidated and nonamidated forms of the peptide. The presence of the amide group was indicated by lack of susceptibility to carboxypeptidase A and Y treatment and was confirmed by the observation that the native CCAP comigrated with the amidated synthetic peptide on HPLC. Native and synthetic CCAP displayed high accelerating activity on a semi-isolated crab heart preparation, whereas the nonamidated synthetic peptide was of much lower potency. The effect of CCAP was both inoand chronotropic. The two pericardial organs of one animal yielded 30-40 pmol of extractable CCAP. Its sequence does not resemble that of any known neuropeptide. However, a "mirror-image" similarity to vasopressin is conspicuous.

Identification and immunocytochemical localization of proctolin in pericardial organs of the shore crab, Carcinus maenas.

The occurrence of proctolin (Arg-Tyr-Leu-Pro-Thr) in crab neurohemal pericardial organs (POs) has been demonstrated by isolation of the pentapeptide by HPLC and manual microsequencing according to the DABITC-PITC double coupling technique. From one pair of POs approximately 5.4 pmol were obtained (= 45 pmol/mg protein). Immunocytochemically, an extensive system of positive structures was found in both whole mount preparations and semithin sections, consisting of numerous varicose fibres of varying diameter and many knoblike neurosecretory terminals abutting upon the epineurium of the PO trunks. The relatively high concentration in the POs as well as the pattern of proctolin-positive fibres and terminals clearly suggest a neurohormonal role of the pentapeptide in decapod crustaceans.