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Biomedical subjects

K A Conrad

Publications and source records attributed to K A Conrad.

At least 37 records · Page 2Linked to original sources
PubMed1989

Comparison of plasma, mononuclear and polymorphonuclear leucocyte vitamin C levels in young and elderly women during depletion and supplementation.

The levels of vitamin C in plasma, mononuclear (MN) and polymorphonuclear (PMN) leucocytes were measured in healthy, free-living, young and elderly women on three occasions over an 8-10-week period: (a) at entry into the study, (b) following 5 weeks of dietary depletion of vitamin C, and (c) following 3 weeks of supplementation with 500 mg of vitamin C per day. The combined mean vitamin C levels (expressed as microgram/10(8) cells) in MN cells were higher than those found in PMN cells at all three times, although the difference was only statistically significant in the depleted state. There were no age-related differences in the levels of vitamin C in plasma, MN or PMN cells at any of the three times. Significant overall differences in vitamin C levels between the entry and depleted and the depleted and supplemented states were observed for plasma and PMN cells but not for MN cells, possibly indicating that plasma and PMN cells are more sensitive indicators of vitamin C status than MN cells. The mean levels of vitamin C found in plasma clearly do 'track' those found in MN and PMN cells. However, attempted correlations between plasma and MN, plasma and PMN, and MN and PMN vitamin C levels at each time proved to be non-significant. In addition, the changes in vitamin C levels from entry to depleted and from depleted to supplemented times were non-significant when comparing plasma to MN and plasma to PMN, whereas the MN vs PMN comparison indicated a significant change in vitamin C levels between the depleted and supplemented states.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The influence of hydrochlorothiazide and tripamide on serum and urinary amylase.

Pancreatitis and asymptomatic elevations of serum amylase have been reported after therapy with thiazide diuretics. In the current study, the effects of hydrochlorothiazide and tripamide treatment on serum and urinary amylase excretion were investigated in 12 hypertensive volunteers. Two patients developed modest elevations of the serum amylase above the normal range after 12 weeks of treatment with hydrochlorothiazide 50 mg daily, but the mean serum amylase did not change. Hydrochlorothiazide did not produce a statistically significant increase in urinary amylase excretion but did reduce the ratio of salivary amylase/creatinine clearance in a two-hour urine collection. Tripamide 10 mg daily had no effect on serum or urinary amylase.

Adult↗
PubMed1988

Doxazosin in patients with hypertension.

The antihypertensive effects and steady-state pharmacokinetics of doxazosin, as well as the bioequivalence of four dosage forms, were studied in 25 hypertensive patients. For an 8 mg daily dose mean Cmax at steady-state for all patients was 108 ng/ml; the mean tmax was 1.8 h. The mean terminal elimination half-life was 22 h. The four tablets containing 1, 2, 4, or 8 mg of doxazosin were bioequivalent in delivering the 8 mg dose. In patients with mild to moderate hypertension, 26-day treatment with doxazosin resulted in blood pressure reduction of 10/7 mmHg in the supine and 13/18 mmHg in the standing position. Adverse effects were generally mild and of brief duration.

Adult↗
PubMed1988

Effects of ketorolac tromethamine on hemostasis in volunteers.

Ketorolac tromethamine, an analgesic agent with prostaglandin synthetase--inhibiting activity, is more active than aspirin in vitro in inhibiting collagen- or arachidonic acid-induced platelet aggregation. In this randomized, double-blind study, 26 volunteers received ketorolac, 30 mg intramuscularly four times a day for 5 days, and placebo, two capsules orally four times a day for at the last 2 study days. The effects of this treatment were compared with those of intramuscular placebo and oral aspirin, two 325 mg capsules, given on the same schedule to eight volunteers. Aspirin at a mean serum concentration of 84 micrograms/ml did not affect prothrombin time, partial thromboplastin time, platelet count, or bleeding time. Ketorolac produced a modest prolongation of the bleeding time, from 4.9 +/- 1.1 minutes (mean +/- SD) to 7.8 +/- 4.0 minutes (p less than 0.005). Ketorolac did not affect the prothrombin time or partial thromboplastin time but was associated with clinically insignificant change in the platelet count from 303 +/- 57 X 10(3)/m3 to 277 +/- 56 X 10(3)/mm3.

Adult↗
PubMed1988

Single versus triplicate measurements of blood pressure and heart rate.

The mean of rapidly repeated duplicate or triplicate measurements is often used in studies of antihypertensive drugs. Forty patients with hypertension had triplicate measurements of blood pressure and heart rate on two occasions, 1 week apart, during placebo treatment. The average difference between the first measurement and the mean of the triplicate measurements was -0.3 mm Hg. The average coefficient of variation for supine and standing, systolic and diastolic blood pressures was 8.4% for the single measurements and 8.0% for the mean of triplicate measurements. The correlations between the first measurements and the mean of triplicate measurements ranged from 0.90 to 0.98 (all p less than 0.01). The average difference between the two visits for all four blood pressure parameters was -0.6 mm Hg for the single measurements and -0.5 mm Hg for the mean of triplicate measurements (all p = NS). These results indicate that 1) blood pressure does not change further after 1 week of placebo treatment, and 2) use of the mean of triplicate measurements of blood pressure and heart rate gives the same result as use of single measurements, and the results are no less variable.

Adult↗
PubMed1987

Antihypertensive effects of parenteral nicardipine alone and in combination with captopril.

We studied the safety and efficacy of intravenous nicardipine alone and in combination with oral captopril. Sixteen patients with essential hypertension received a single oral dose of captopril, 50 mg, to be certain that excessive hypotension would not occur. Nicardipine was given intravenously as a 2 mg bolus, followed by an infusion at a rate designed to lower the supine diastolic blood pressure at least 10 mm Hg; then oral captopril, 50 mg, or placebo was given. The next week, nicardipine was again infused, but the alternate oral treatment was given. Intravenous nicardipine reduced blood pressure from 156 +/- 15/101 +/- 5 mm Hg (mean arterial blood pressure 120 +/- 6 mm Hg) to 140 +/- 11/88 +/- 4 mm Hg (mean arterial blood pressure 105 +/- 5 mm Hg). When captopril was added to nicardipine, the mean arterial blood pressure fell an additional 8 mm Hg but the heart rate did not increase. The combination of angiotensin-converting enzyme inhibition and calcium channel blockage produces additive antihypertensive effects without additional reflex tachycardia.

Administration, Oral↗
PubMed1986

Xylose disposition in humans as a function of age.

D-xylose disposition was examined in 24 healthy men between 32 and 85 years of age. Xylose was administered as a 5 gm iv infusion and as a 25 gm po solution. Serum xylose concentrations and urinary excretion of intact xylose were determined. There were statistically significant inverse relationships with age for each of the following parameters after intravenous infusion: elimination rate constant (r2 = 0.71); systemic clearance (r2 = 0.66); renal clearance (r2 = 0.66); and nonrenal clearance (r2 = 0.35). Similar inverse relationships were found after oral dosing for the elimination rate constant (r2 = 0.69) and renal clearance (r2 = 0.54). There was no significant age relationship for the apparent volume of distribution or the steady-state volume of distribution. The percentage of the oral and intravenous dose recovered in urine up to 5 hours after dosing was significantly and inversely correlated with age. The implications of the latter finding are discussed with regard to the interpretation of the xylose tolerance test used to assess gastrointestinal absorptive capacity.

Administration, Oral↗
PubMed1986

Antihypertensive and biochemical dose-response study of tripamide.

Tripamide is an experimental sulfonamide-derived diuretic antihypertensive agent. Twenty-four hospitalized patients with essential hypertension received placebo followed by 10, 25, 50, or 100 mg of tripamide daily in a randomized, double-blind design. All doses of tripamide significantly lowered standing arterial pressure. Changes in blood pressure, heart rate, and weight were not dose related, but the decrease in mean arterial pressure was significantly related to both age (P less than 0.02) and pretreatment blood pressure (P less than 0.05). Serum potassium levels were lowered significantly by the 25 and 100 mg daily doses of tripamide, whereas all doses of tripamide significantly reduced serum chloride levels and produced an increase in serum uric acid levels. Disparate time courses of antihypertensive and diuretic effects and the lack of a relationship between the increase in urine volume and the change in blood pressure suggest an additional antihypertensive action of tripamide or a delayed physiologic adaptation to volume depletion. Equal antihypertensive effects over the range of 10 to 100 mg/day, but greater hypokalemia at higher doses, suggest that future studies should employ the lower doses of tripamide.

Adult↗
PubMed1986

Effect of tripamide on glucose tolerance in patients with hypertension.

The effects of tripamide and hydrochlorothiazide on blood pressure and glucose tolerance were studied in 20 hypertensive patients, half of whom had type II diabetes mellitus. Each patient underwent intravenous glucose tolerance testing before and after 4 weeks of treatment with tripamide, 10 mg, and, at a separate time, hydrochlorothiazide, 50 mg. Both tripamide and hydrochlorothiazide lowered blood pressure; for both drugs, the magnitude of the reduction in mean arterial pressure was positively correlated with the pretreatment mean arterial pressure. Hydrochlorothiazide produced a greater fall in serum potassium than did tripamide. In the nondiabetics, neither drug produced a significant change in the glucose disappearance curve or the plasma insulin response. In the diabetics, hydrochlorothiazide produced an increase in serum glucose levels, but the plasma insulin response, which was blunted in comparison to the nondiabetics, did not change. Tripamide did not affect serum glucose or plasma insulin levels in either group of patients. Tripamide at a dose of 10 mg daily does not affect glucose tolerance in either nondiabetic hypertensive patients or patients with type II diabetes mellitus.

Administration, Oral↗
PubMed1986

Effects of meals on hemodynamics: implications for antihypertensive drug studies.

The ingestion of food is known to affect blood pressure and heart rate, but food is often allowed in patients under observation for antihypertensive drug effects. Seventy-seven patients with essential hypertension were observed for 8 hours after a 16-hour fast. Thirty-six continued to fast, 20 ate a high-carbohydrate meal, and 21 ate a meal of their own choice. Blood pressure and heart rate did not change during fasting, but both meals lowered mean supine and standing diastolic blood pressures during the subsequent 4 hours by 3 to 7 mm Hg (P less than 0.001). The high-carbohydrate meal reduced supine systolic blood pressure by 6 mm Hg (P less than 0.0001). Both meals increased supine and standing heart rates by 5 to 8 bpm (P less than 0.001). After the self-selected meal, standing systolic blood pressure increased in younger patients but decreased in older patients. Food ingestion during antihypertensive drug studies may interfere with the interpretation of results and should be avoided whenever possible.

Adult↗
PubMed1986

Cimetidine absorption in humans during sucralfate coadministration.

Cimetidine absorption after a single 300 mg oral dose was evaluated in six normal subjects in the absence or presence of sucralfate. Sucralfate was ingested four times a day for 2 days prior to and for two additional doses on the day of cimetidine ingestion. Sucralfate coadministration had no statistically significant influence on the rate or extent of cimetidine absorption.

Administration, Oral↗
PubMed1985

Gastrointestinal absorption as a function of age: xylose absorption in healthy adults.

Xylose oral absorption was examined in 24 healthy male subjects ranging in age from 32 to 85 years. Absorption was evaluated from xylose plasma concentration-time data after administration of a 25 gm po or a 5 gm iv dose. There was no relationship between various estimates of the rate of absorption and age. The absolute oral bioavailability or the extent of xylose absorption showed no relationship to age in our population. In contrast with previous suggestions, xylose absorption does not decline with age. General statements of decreased gastrointestinal absorption efficiency as a function of age may not be correct.

Administration, Oral↗
PubMed1984

Innovations in drug delivery.

With recent innovations in pharmaceutical technology, important new methods of drug delivery have joined established ones. Prolonged-release oral preparations can provide precisely controlled drug delivery, which permits less frequent dosage of drugs with a short elimination half-life and thus improves compliance. These preparations also can narrow fluctuations in plasma levels, which maximizes efficacy and minimizes toxicity. Sustained-release intraocular and transcutaneous preparations offer similar advantages. Infusion pumps provide predictable systemic delivery of drugs that cannot be given orally or transcutaneously. Further innovations can undoubtedly be expected. When the therapeutic alternatives include a prolonged-release preparation, its potential advantages should be weighed against its potential disadvantages. Although some of these preparations cost more, this disadvantage may be outweighed by potential advantages.

Administration, Topical↗
PubMed1983

Lidocaine elimination: effects of metoprolol and of propranolol.

The effects of administration of metoprolol and propranolol on lidocaine elimination were studied in six healthy young men who did not smoke. Each received three single intravenous doses of lidocaine (2.5 to 3.0 mg/kg injected over 10 min): one alone, one after 1 day pretreatment with propranolol (40 mg orally every 6 hr), and one after 1 day pretreatment with metoprolol (50 mg orally every 6 hr). Lidocaine clearance was 0.88 +/- 0.28 l X hr-1 X kg-1 before beta blockade, 0.61 +/- 0.20 l X hr-1 X kg-1 during metoprolol dosing, and 0.47 +/- 0.16 l X hr-1 X kg-1 during propranolol dosing. There was no correlation between the change in lidocaine elimination and the steady-state concentrations of metoprolol or propranolol, nor between the change in lidocaine clearance and the change in resting heart rate produced by either beta blocker. Metoprolol and propranolol reduce lidocaine elimination significantly.

Adult↗
PubMed1983

HPLC analysis of creatinine in human plasma and urine.

A simple, rapid, reproducible HPLC method is described for the analysis of creatinine in human plasma and urine. Creatinine is isolated from plasma proteins prior to HPLC analysis by ultrafiltration using a micropartition system. The technique requires only 0.2 ml of plasma and the recovery of creatinine is complete. Results from the HPLC analysis are compared with those from an automated (colorimetric) analysis. The retention time of creatinine is 2.6 min.

Autoanalysis↗