Comparative evaluation of the effects of isradipine and diltiazem on antipyrine and indocyanine green clearances in elderly volunteers.

Calcium antagonists have been shown to depress hepatic enzymes and accelerate hepatic blood flow. This study was designed to compare the effects of two calcium antagonists, isradipine and diltiazem, on antipyrine and indocyanine green (ICG) clearances in the elderly. Eighteen elderly subjects (aged 65 to 80 years) received either isradipine (5 mg every 12 hours), diltiazem (90 mg every 8 hours), or placebo (every 12 hours) for 4 days. On the third day after the study treatment, a 0.5 mg/kg dose of ICG was administered. Blood samples were obtained over 20 minutes for HPLC determination of ICG plasma concentrations. Ten minutes later, subjects ingested 1.2 gm antipyrine. Blood samples were obtained over 48 hours for HPLC determination of antipyrine plasma concentrations. Mean +/- SD antipyrine clearance after diltiazem (0.0258 +/- 0.0065 L/hr/kg) was significantly lower than that observed after isradipine (0.0334 +/- 0.0098 L/hr/kg) or placebo (0.0329 +/- 0.0082 L/hr/kg). Antipyrine clearance after isradipine was not significantly different from that after placebo. Mean +/- SD ICG clearances after diltiazem (9.17 +/- 1.35 ml/min/kg) or isradipine (9.57 +/- 1.82 ml/min/kg) were significantly higher than that observed after placebo (8.06 +/- 1.45 ml/min/kg). These findings suggest that diltiazem, but not isradipine, affects hepatic enzyme activity in the elderly. Both agents accelerate ICG clearance, a marker of hepatic blood flow.

Effects of aluminum and magnesium antacids and ranitidine on the absorption of ciprofloxacin.

The effect of an antacid (Maalox) and ranitidine administration on the absorption of ciprofloxacin was evaluated in healthy male volunteers who were enrolled in three separate studies. Each study was designed at a three- or four-period crossover and included the administration of 750 mg ciprofloxacin alone as a control treatment. Treatments that were evaluated included the administration of ciprofloxacin 5 to 10 minutes, 2 hours, 4 hours, and 6 hours after a single 30 ml dose of antacid; the administration of antacid 2 hours after ciprofloxacin was given; and the administration of ciprofloxacin 2 hours after a 200 mg ranitidine tablet. Administration of antacid within 4 hours before ciprofloxacin dose resulted in a significant decrease in ciprofloxacin absorption (p less than 0.05). Percentages of relative bioavailability compared with control values were 15.1%, 23.2%, and 70% for the 5 to 10 minute, 2 hour, and 4 hour antacid pretreatments, respectively. Administration of antacid 6 hours before or 2 hours after the ciprofloxacin dose did not affect absorption. Ranitidine did not alter ciprofloxacin absorption. Antacids that contain magnesium and aluminum salts may reduce the absorption of ciprofloxacin. The extent of this interaction appears to increase as the time between administration of the two drugs decreases. Ranitidine is suggested as an alternative to antacids for patients receiving treatment with ciprofloxacin.

Comparative evaluation of the effects of labetalol, verapamil and diltiazem on antipyrine and indocyanine green clearances.

The effects of labetalol, diltiazem and verapamil on antipyrine and indocyanine green clearance were evaluated in a placebo-controlled, repeated measures evaluation. Twelve healthy subjects received either labetalol (200 mg every 12 hours), diltiazem (90 mg. every 8 hours), verapamil (80 mg every 8 hours), or placebo (every 12 hours) for 4 days. On the morning of Day 3 immediately following their dose, the subjects assumed the supine position for 90 minutes, after which time a 0.5 mg/kg dose of indocyanine green was administered. Blood samples were obtained serially over a 20 minutes period for indocyanine green plasma concentration determinations by HPLC. Ten minutes later, subjects ingested a 1.2 Gm. dose of antipyrine and blood samples were obtained over a 48 hour period for antipyrine plasma concentration determinations by HPLC. A 2 week washout period separated treatment sequences. Mean (SD) antipyrine clearance (L/hr/kg) following diltiazem [0.028 (0.010)] and verapamil [0.030 (0.012)] treatment was significantly lower than that observed following placebo [0.039 (0.012)]. Antipyrine clearance following labetalol administration [0.033 (0.010)] was not significantly different from that observed following placebo, diltiazem or verapamil administration. No effects of these drugs on indocyanine green clearance could be detected.

Lidocaine absorption and metabolism after oropharyngeal application in young and young-elderly adults.

The purpose of this study was to evaluate the effect of age on lidocaine absorption and metabolism after application to the oropharynx and vocal cords in a manner similar to preparation for flexible fiberoptic bronchoscopy. Five healthy volunteers were studied in each of two age groups: from 25 to 37 and 60 to 68 years of age. Each volunteer had a total of lidocaine 300 mg administered as a gargle, gel, or directly to the vocal cords. Blood samples and expectorant were collected to determine concentrations of lidocaine and its metabolites, monoethylglycinxylidide (MEGX) and glycinxylidide (GX). No differences in peak plasma lidocaine concentrations, 2.09 +/- 1.28 mumol/L (1 microgram/mL = 4.27 mumol/L) in young subjects, and 2.35 +/- 0.85 mumol/L in young-elderly subjects, or lidocaine AUC were seen between the two age groups. Lidocaine recovered in expectorant ranged from 96 to 168 mg. This study suggests that, over the age range studied, increased age does not impair lidocaine absorption from the oropharynx or lidocaine metabolism when topical lidocaine is used during flexible fiberoptic bronchoscopy.