Severe arrhythmia as a result of the interaction of cetirizine and pilsicainide in a patient with renal insufficiency: first case presentation showing competition for excretion via renal multidrug resistance protein 1 and organic cation transporter 2.

A 72-year-old woman with renal insufficiency who was taking oral pilsicainide (150 mg/d) complained of feeling faint 3 days after she was prescribed oral cetirizine (20 mg/d). She was found to have a wide QRS wave with bradycardia. Her symptoms were relieved by termination of pilsicainide. The plasma concentrations of both drugs were significantly increased during the coadministration, and the cetirizine concentration decreased on cessation of pilsicainide despite the fact that treatment with cetirizine was continued, which suggested that the fainting was induced by the pharmacokinetic drug interaction. A pharmacokinetic study in 6 healthy male volunteers after a single dose of either cetirizine (20 mg) or pilsicainide (50 mg), or both, found that the renal clearance of each drug was significantly decreased by the coadministration of the drugs (from 475 +/- 101 mL/min to 279 +/- 117 mL/min for pilsicainide and from 189 +/- 37 mL/min to 118 +/- 28 mL/min for cetirizine; P = .008 and .009, respectively). In vitro studies using Xenopus oocytes with microinjected human organic cation transporter 2 and renal cells transfected with human multidrug resistance protein 1 revealed that the transport of the substrates of these transporters was inhibited by either cetirizine or pilsicainide. Thus elevated concentrations of these drugs as a result of a pharmacokinetic drug-drug interaction via either human multidrug resistance protein 1 or human organic cation transporter 2 (or both) in the renal tubular cells might have caused the arrhythmia in our patient. Although cetirizine has less potential for causing arrhythmias than other histamine 1 blockers, such an interaction should be considered, especially in patients with renal insufficiency who are receiving pilsicainide.

Comparative study of taste disturbance by losartan and perindopril in healthy volunteers.

The aim of this study was to compare the degree of taste disturbance by losartan, an angiotensin II receptor blocker, with that of perindopril, an angiotensin-converting enzyme inhibitor. Perindopril erbumine (2 mg), losartan potassium (25 mg), or vehicle was given to Japanese volunteers (n = 7) for 14 days in a randomized, placebo-controlled, 3-way crossover design with a 14-day washout period. Gustometry by filter-paper test and electrogustometry were performed before and at the end of each trial. Plasma renin activity (PRA) and serum and salivary zinc concentrations were measured. One subject dropped out because of a perindopril-induced dry cough, but no one claimed a taste disturbance. Detection thresholds of 4 basic tastes (sweet, salty, sour, and bitter) by the paper-disc test and electrogustometry were significantly worsened, and plasma renin activity was elevated by the drugs, whereas the deteriorating effects of 2 drugs did not significantly differ. These drugs did not affect zinc concentrations in plasma and saliva. It was concluded that losartan and perindopril similarly alter taste sensitivity during repeated dosing of the drugs.

Dosing time-dependent variation in the hypocalcemic effect of calcitonin in rat.

Dosing time-dependent variation in the hypocalcemic effect of salmon calcitonin was examined in rats under a 12-h light-dark cycle. In both a single-dosing study with normal rats and a repeated-dosing study with hypercalcemic rats (induced by chronic vitamin-D dosing), we consistently observed that the hypocalcemic effect of calcitonin was greater when the drug was given at 14 h after lights on than that at 2 h after lights on. The reduction in urinary deoxypyridinoline excretion, a marker of bone resorption, was also greater when calcitonin was given at 14 h after lights on. Urinary excretion of Ca was not affected by the drug. Pharmacokinetic profiles of calcitonin after a single dosing did not differ between the two trials. These results indicate that the hypocalcemic effect of calcitonin is greater after dosing in the early dark phase (14 h after lights on) than after dosing in the early light phase (2 h after lights on). A time-dependent variation in the sensitivity to the drug of osteoclasts, but not renal tissues, may be involved in the mechanism of this event.

Chronopharmacology of oxacalcitriol in 5/6 nephrectomized rats.

We previously reported on the merits of the chronopharmacological effects of 1,25(OH) 2 vitaminD3 in 5/6 nephrectomized rats (Tsuruoka et al, Life Scineces 2002; 71: 1809-1820). In this study, the chronopharmacological effect of 22-oxacalcitriol (OCT), a newly developed active vitaminD3 analogue with less calcemic activity, was evaluated by a single and repeated dosing of the drug. The 5/6 nephrectomized animals were kept in rooms with a 12-h light/dark cycle. Single (12.5 microg/kg, i.v.) and repeated (5 microg/kg, i.v. three times a week for 12 weeks) dosing of OCT or vehicle was given at either 2 hours after lights on (2HALO) or 14 hours after lights on (14HALO). The severity of hypercalcemia and hyperphosphatemia was significantly milder when the drug was given at 14HALO. Serum concentrations of total OCT and albumin of the 2HALO and 14HALO trials did not differ significantly. The decrease of parathyroid hormone concentration was greater in the 14HALO trial while the increase in urinary ratio of Ca to creatinine was greater in the 2HALO trial. The suppression of urinary deoxypyridinoline excretion, an index of bone resorption capacity of osteoclast, and the increase in bone density of both femurs were greater in the 14HALO trial. These results suggest that the adverse reactions of OCT were ameliorated and its efficacy was enhanced after dosing of the drug at 14HALO. Chronopharmacological differences of OCT were more prominent than those seen with other vitamin D analogues. Dosing-time-dependent variation in the sensitivity of the drug to osteoclast were involved in the mechanisms of these events.

Acute digoxin loading reduces ABCA8A mRNA expression in the mouse liver.

Human ABCA8, a new member of the ATP binding cassette (ABC) transporter family, transports certain lipophilic drugs, such as digoxin. To investigate the roles of this transporter, we cloned a mouse homologue of ABCA8, from a mouse heart cDNA library, named ABCA8a. The deduced mouse ABCA8a protein is 66% identical with that of human ABCA8 and possesses features common to the ABC superfamily. It was found that ABCA8a was mainly expressed in the liver and heart, similar to human ABCA8. We further evaluated the effect of acute digoxin (a substrate for ABCA8) intoxication on the mRNA expression of ABCA8 using northern blotting with a 3' non-coding region as a probe to avoid cross-hybridization with other ABCA genes. Following acute digoxin infusion, the mRNA expression of ABCA8 was significantly reduced in the liver 12-24 h after injection (14.7% of vehicle treatment), but not in the heart and kidney. Real-time quantitative polymerase chain reaction analysis confirmed the reduction in ABCA8a mRNA. Similar reductions in ABCA5, ABCA7, ABCA8b and ABCA9 mRNA were also observed. A comparable amount of digitoxin did not affect ABCA8a mRNA expression in the liver. The results suggest that ABCA8 may play a role in digoxin metabolism in the liver.

Angiotensin II receptor blocker-induces blunted taste sensitivity: comparison of candesartan and valsartan.

AIMS: To compare the degree of taste disturbance by candesartan and valsartan. METHODS: Candesartan cilexetil (4 mg day(-1)), valsartan (40 mg day(-1)), or vehicle was given to subjects (n = 8) for 13 days in a randomized, placebo-controlled, three-way crossover design with a 14-days washout period. Gustometry by filter-paper test and electrogustometry were performed before and at the end of each trial. Plasma renin activity and zinc concentrations in serum and saliva were measured. RESULTS: Detection thresholds of four basic tastes (sweet, salty, sour and bitter) by paper-disc test and electrogustometry were significantly worsened and plasma renin activity was elevated after the test, while the effects of two drugs did not significantly differ. These drugs did not affect zinc concentrations. CONCLUSION: Both candesartan and valsartan similarly alter taste sensitivity after the repeated dosing of the drug.

Subclinical alteration of taste sensitivity induced by candesartan in healthy subjects.

AIMS: There have been case reports of taste disturbance for the angiotensin II receptor blockers losartan and valsartan, but not for candesartan. This study was undertaken to examine whether candesartan causes taste disturbance. METHODS: Candesartan cilexetil (4 mg day(-1)) or vehicle was given to healthy volunteers (n = 8) for 7 days in a randomized, double-blind, placebo-controlled, cross-over design with a 2-week washout period. Clinical gustometry using the filter-paper disc test and electrogustometry were sequentially performed before and at the end of each trial. Serum and salivary zinc concentrations were also measured. RESULTS: Detection thresholds of four basic tastes (sweet, salty, sour and bitter) determined by the paper disc test were significantly (P < 0.05 in all tests) worsened (i.e. score of test increased) after repeated dosing of the drug, although the subjects did not notice such changes. The mean +/- SEM (and 95% CI) scores of the four tastes at just before the seventh dosing of candesartan or vehicle was 3.38 +/- 0.32 (3.02, 3.74) and 2.63 +/- 0.18 (2.18, 3.08) for sweetness, 3.63 +/- 0.38 (4.49, 2.77) and 2.63 +/- 0.26 (3.27, 1.98) for salt, 4.01 +/- 0.42 (3.04, 4.98) and 2.61 +/- 0.32 (3.35, 1.87) for sourness, 4.01 +/- 0.38 (3.22, 4.80) and 2.99 +/- 0.33 (2.24, 3.74) for bitterness, for candesartan and placebo, respectively. Electrogustometry confirmed the candesartan-related taste disturbance. Serum and salivary zinc concentrations were not influenced by candesartan. CONCLUSIONS: These data suggest that candesartan subclinically reduces taste sensitivity after repeated dosing in healthy subjects. Because similar events are reported for losartan and valsartan in case reports, this adverse effect might be a class effect of angiotensin-II receptor blockers (ARBs).

Hemodynamics during chronic amiodarone administration in Japanese patients with idiopathic dilated cardiomyopathy and ventricular arrhythmia: a retrospective study.

OBJECTIVES: Nonischemic heart disease, especially idiopathic dilated cardiomyopathy, is relatively common among Japanese patients receiving amiodarone for concomitant ventricular arrhythmia, but the hemodynamic effects of amiodarone in these Japanese patients are unclear. The hemodynamic changes during chronic amiodarone administration were retrospectively studied in patients with idiopathic dilated cardiomyopathy and ventricular arrhythmia. METHODS: Fifty-two patients [42 males, 10 females, 53 +/- 2 years (mean age +/- SE)] with ventricular tachyarrhythmia and idiopathic dilated cardiomyopathy with left ventricular ejection fraction of 27 +/- 1% (mean +/- SE) were treated with 200-400 mg daily of oral amiodarone as the loading dose for the initial 14 days and 100-200 mg daily maintenance dose for a further 6 months. No patients were taking beta-blockers or positive inotropic drugs. Echocardiographic examination was performed before (baseline), at week 2 and at month 6 of amiodarone therapy. Twenty four-hour Holter monitoring during the same time period was also performed in 34 patients. Seventeen patients underwent right heart catheterization before and at week 2. RESULTS: Echocardiographic measurements showed no significant change in left ventricular end-diastolic dimension, although there was a slight increase in fractional shortening from 16 +/- 1% to 19 +/- 1% (p < 0.05) and 18 +/- 1% (mean +/- SE) (p < 0.01) at week 2 and month 6 of amiodarone therapy, respectively. Amiodarone markedly reduced the mean heart rate and the frequency of premature ventricular complexes on ambulatory monitoring. The cardiac index did not change and the pulmonary capillary wedge pressure tended to decrease slightly at week 2 in the 17 patients who underwent catheterization. CONCLUSIONS: This retrospective study showed no worsening of the hemodynamic state during chronic amiodarone administration in Japanese patients with idiopathic dilated cardiomyopathy and ventricular arrhythmia.

Beta2-microglobulin adsorption column reduces digoxin trough level during hemodialysis: three case reports.

We have previously reported that a beta2-microglobulin adsorption column for the treatment of dialysis-related amyloidosis decreased serum digoxin concentration in renal failure patients. Because the distribution volume of digoxin is high, it is uncertain whether the repetitive use of this column influences the pharmacokinetics of digoxin in renal failure patients. We have observed 3 renal failure patients whose trough serum digoxin concentrations were significantly reduced by the repetitive use of tandem beta2-microglobulin adsorption columns for treatment of dialysis-related amyloidosis. These patients experienced symptomatic elevation of their heart rates in parallel with a significant reduction in serum digoxin concentrations. Termination of the use of the adsorption column improved the symptoms in 1 patient; however, severe arthritic pain caused by amyloidosis relapsed. Dosage of digoxin was increased in 2 other patients with continuous treatment by the column. Their digoxin concentrations increased, and their heart rates decreased without any deterioration of joint pain. We have demonstrated that the repetitive use of the beta2-microglobulin adsorption column in tandem with standard hemodialysis actually decreases trough digoxin concentration in renal failure patients. Careful monitoring and alteration of digoxin dosage regimens are needed under these circumstances.

Chronotherapy of high-dose active vitamin D3 in haemodialysis patients with secondary hyperparathyroidsm: a repeated dosing study.

AIMS: Renal osteodystrophy is the major complication in patients with end-stage renal failure. Oral or intravenous vitamin D3 (D3) is given to these patients, but severe hypercalcaemia sometimes interrupts this therapy. This study was undertaken to determine whether the effectiveness and safety of D3 also depend on its dosing time during a repeated treatment. METHODS: A higher dose (3 micro g) was given orally to 13 haemodialysis patients at 08.00 h or 20.00 h for 12 months by a randomized, cross-over design. RESULTS: Three patients were withdrawn due to severe hypercalcaemia after switching from 08.00 h to 20.00 h dosings. The elevation in serum calcium concentration was significantly (P < 0.001) greater during the 08.00 h dosing in the remaining ten patients. Mean serum Ca concentration after the trial was 10.92 (95% confidence interval (CI) 10.79, 11.06) and 9.55 mg dl-1 (95% CI 9.30, 9.71) by 08.00 h and 20.00 h dosing, respectively. On the other hand, the suppression of the elevated serum parathyroid hormone (PTH) and subsequent increment in bone density were significantly greater during the 08.00 h dosing. Mean PTH concentration after the trial was 414 (95% CI 360, 475) and 220 pg ml-1 (95% CI 202, 249) by 08.00 h and 20.00 h dosing, respectively (P = 0.02). Mean increment of bone density after the trial was 22 (95% CI 8, 32) and 57 g cm-3 (95% CI 43, 83) by 08.00 h and 20.00 h dosing, respectively (P = 0.04). CONCLUSION: These results indicate that a higher dose of oral D3 is more effective and safe after dosing at evening in patients with renal osteodystrophy.

Amiodarone distribution in human tissues after long-term therapy: a case of arrhythmogenic right ventricular cardiomyopathy.

The tissue distribution of amiodarone and desethylamiodarone, its active metabolite, was examined in an autopsied case, an 85-year-old man, with arrhythmogenic right ventricular cardiomyopathy (ARVC) who had been receiving amiodarone for 4 years. High concentrations of amiodarone, a very highly lipophilic compound, were found in adipose and bone marrow tissues. Despite a low dose (100 mg daily), the concentrations of amiodarone were higher in the epicardial fat (570.4 microg/g) and in the right atrium (165.3 microg/g) than previously reported in patients with other cardiac diseases. The ratios of amiodarone/ desethylamiodarone concentrations in both tissues were >1. This unique distribution demonstrates the involvement of histological characteristics of ARVC, such as fatty replacement of myocardium. We anticipate that a low dose of amiodarone would be effective in preventing arrhythmia in some patients with ARVC.

Beta-blocker therapy combined with low-dose pimobendan in patients with idiopathic dilated cardiomyopathy and chronic obstructive pulmonary disease: report on two cases.

Pimobendan is an inotropic and vasodilating drug with phosphodiesterase (PDE) III-inhibiting and calcium-sensitizing effects. It may also have a bronchodilatory effect by inhibiting PDE III in airway smooth muscle. We tried a beta-blocker combined with low-dose pimobendan in 2 patients who had refractory heart failure of NYHA functional class III or IV with idiopathic dilated cardiomyopathy (DCM) and chronic obstructive pulmonary disease (COPD). Both of them had previously failed to tolerate beta-blocking drugs because of the exacerbation of bronchospasm. After pimobendan was administered at 1.25 to 2.5 mg daily, metoprolol could be successfully introduced from a low dose of 1.25 mg daily without decreasing the peak expiratory flow rate. Over the next 1 to 2 years, they have continued beta-blocker therapy. One is currently receiving 10 mg daily of bisoprolol and another is taking 15 mg daily of metoprolol, and both are in NYHA functional class II without worsening heart failure or COPD. The combination of beta-blocker with low-dose pimobendan may be helpful for patients with DCM and COPD, but further clinical investigation is required.

Nitric oxide production modulates cyclosporin A-induced distal renal tubular acidosis in the rat.

Cyclosporine A (CsA) causes distal renal tubular acidosis (dRTA) in humans and rodents. Because mice deficient in nitric-oxide (NO) synthase develop acidosis, we examined how NO production modulated H+ excretion during acid loading and CsA treatment in a rat model. Rats received CsA, L-arginine (L-Arg), or N omega-nitro-L-arginine methyl ester (L-NAME), or combinations of CsA and L-NAME or L-Arg, followed by NH4Cl (acute acid load). In vehicle-treated rats, NH4Cl loading reduced serum and urine (HCO3-) and urine pH, which was associated with increases in serum [K+] and [Cl-] and urine NH3 excretion. Similar to CsA (7.5 mg/kg), L-NAME impaired H+ excretion of NH4Cl-loaded animals. The combination CsA and L-NAME reduced H+ excretion to a larger extent than either drug alone. In contrast, administration of L-Arg ameliorated the effect of CsA on H+ excretion. Urine pH after NH4Cl was 5.80 +/- 0.09, 6.11 +/- 0.13*, 6.37 +/- 0.16*, and 5.77 +/- 0.09 in the vehicle, CsA, CsA + L-NAME and CsA + L-Arg groups, respectively (*P < 0.05). The effect of CsA and alteration of NO synthesis were mediated at least in part by changes in bicarbonate absorption in perfused cortical collecting ducts. CsA or L-NAME reduced net HCO3- absorption, and, when combined, completely inhibited it. CsA + L-Arg restored HCO3- absorption to near control levels. Administration of CsA along with L-NAME reduced NO production to below levels observed with either drug alone. These results suggest that CsA causes dRTA by inhibiting H+ pumps in the distal nephron. Inhibition of NO synthesis may be one of the mechanisms underlying the CsA effect.

Amiodarone decreases plasma brain natriuretic peptide level in patients with heart failure and ventricular tachyarrhythmia.

Brain natriuretic peptide (BNP) is a powerful neurohormonal marker of left ventricular function and prognosis. Amiodarone either has no effect or improves the haemodynamics in patients with left ventricular dysfunction, but its effect on BNP is unknown. This study evaluated the effect of amiodarone on plasma BNP level in patients with heart failure and ventricular tachyarrhythmia. Plasma BNP level was studied in 46 patients with heart failure ventricular tachyarrhythmia, before (baseline) and at week 2 and months 1, 3 and 6 of amiodarone treatment. In addition, 21 patients with heart failure and ventricular tachyarrhythmia, who received an implantable cardioverter defibrillator, but not amiodarone, were studied on the same schedule. All patients had previously received potent vasodilator and beta-blocker therapy. Echocardiography and Holter monitoring were also performed. Amiodarone significantly decreased plasma BNP levels at week 2 to month 6 during therapy. Heart rates and frequencies of premature ventricular complexes were markedly reduced by amiodarone. Echocardiographic findings did not show a change in left ventricular end-diastolic dimensions, despite a slight increase in fraction shortening at month 6 during amiodarone therapy. The above parameters showed no change in patients without amiodarone. The effect of heart rate, premature ventricular complexes, fraction shortening, serum creatinine or thyroid stimulating hormone level was not significantly associated with decrease in BNP level during amiodarone therapy by a multivariate analysis. Among amiodarone-treated patients, mortality was higher in 24 with BNP levels >/=100 pg/ml at month 6 than in 22 with BNP levels <100 pg/ml during a mean follow-up period of 31 months. Amiodarone appears to have a decreasing effect on plasma BNP level, as well as an antiarrhythmic effect, in patients with heart failure and ventricular tachyarrhythmia.

Functional analysis of ABCA8, a new drug transporter.

We examined the transport capacity in Xenopus laevis oocytes of human EST KIAA0822/ABCA8, a member of the ABC superfamily. Substrates of ABCC2/MRP-2 such as [14C]estradiol-beta-glucuronide, taurocholate, and LTC4, and of organic anion transporter (OAT), such as para-aminohippuric acid, ochratoxin-A, were significantly accumulated while tetraethylammonium and doxorubicin were not. The transport of [14C]estradiol-beta-glucuronide was ATP-dependent and K(m) and V(max) values of 30.4microM and 66.9pmol/h/egg, respectively, were estimated. The transport of [14C]estradiol-beta-glucuronide was inhibited by substrates/inhibitors of ABCC2/MRP-2, but not by those of the organic cation transporter and multidrug resistance protein (MDR)-1. KIAA0822/ABCA8 possesses two ATP-binding sites and fourteen transmembrane domains. Northern blot analysis revealed expression in most organs, especially in heart, skeletal muscle, and liver. Thus, ABCA8 is a new member of the xenobiotic transporter ABC-subfamily.

Effect of low-dose amiodarone on atrial fibrillation or flutter in Japanese patients with heart failure.

The efficacy and safety of amiodarone in the management of atrial fibrillation (AF) or flutter in 108 Japanese patients with heart failure was retrospectively examined. Thirty-four (41%) of the 82 patients who were in sinus rhythm after 1 month of amiodarone administration had their first recurrence, 70% of cases occurring within 1 year of initiation. The cumulative rates of maintenance of sinus rhythm were 0.68, 0.55, and 0.47 at 1, 3, and 5 years, respectively. Amiodarone was more effective in maintaining sinus rhythm in patients with paroxysmal AF or flutter than in those with the persistent form (p<0.05). The cumulative rates for cases that remained in permanent AF were 0.04, 0.11, and 0.14 at 1, 3, and 5 years, respectively. Apart from suppressing AF, the mean heart rate during Holter monitoring was significantly decreased with amiodarone therapy in cases of permanent AF. Adverse effects requiring the discontinuation of amiodarone therapy occurred in 16% of patients. Low-dose amiodarone therapy may prevent AF or flutter in Japanese patients with heart failure.