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Biomedical subjects

S C Olson

Publications and source records attributed to S C Olson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pharmacokinetics of quinapril and its active metabolite quinaprilat during continuous ambulatory peritoneal dialysis.

The pharmacokinetics of quinapril, a novel angiotensin converting enzyme (ACE) inhibitor, and its active metabolite, quinaprilat, were determined following a single 20-mg oral dose of quinapril in six patients with chronic renal failure maintained on continuous ambulatory peritoneal dialysis (CAPD). Overall, quinapril was well tolerated by these CAPD patients, with mild and transient side effects, not unexpected in this clinical setting, which included pruritus, headache, nausea, and cough. Blood pressure reduction was observed in four of six patients, with onset reliably two to four hours after dosing and duration up to 48 hours, associated with quinaprilat concentrations in plasma above 90 ng/mL for at least 33 hours postdose. Two patients experienced significant hypotension, systolic blood pressure below 90 mm Hg, which responded promptly to oral fluid administration and/or reduction in dialysate tonicity. The pharmacokinetic profile of quinapril in these CAPD patients was not significantly different from that previously observed in healthy subjects with normal renal function and in patients with moderate to severe renal dysfunction not yet requiring dialysis (RDND). The apparent elimination half-life of quinapril was approximately one hour, with negligible dialysate excretion. The pharmacokinetic profile of quinaprilat in these CAPD patients was similar to that previously observed in patients with RDND. The elimination half-life of quinaprilat was markedly prolonged when compared to that in healthy subjects and averaged 20 hours, with only a small amount of quinaprilat excreted in dialysate (mean = 2.6% of total dose).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Pharmacokinetics of quinapril and its active metabolite, quinaprilat, in patients on chronic hemodialysis.

The pharmacokinetics of quinapril and its active metabolite, quinaprilat, were evaluated in 12 patients with end-stage renal disease (ESRD) on chronic hemodialysis. Each subject received a single 20-mg oral dose of quinapril 4 hours before a 4-hour hemodialysis treatment. Serial dialysate and blood samples were obtained over 4 and 96 hours, respectively. Samples were analyzed for quinapril and quinaprilat concentrations by gas chromatography. Mean tmax and Cmax values for quinapril were 1.2 hours and 129 ng/mL, respectively. Only one patient had detectable quinapril dialysate concentrations which accounted for 2.8% of the quinapril dose. Mean apparent plasma clearance for quinapril was 1275 mL/min with a mean half-life of 1.7 hours. Quinapril was extensively de-esterified to its diacid metabolite, quinaprilat. Mean tmax and Cmax for quinaprilat were 4.5 hours and 671 ng/mL, respectively. Mean apparent plasma clearance for quinaprilat was 24.0 mL/min with a mean half-life of 17.5 hours. As with quinapril, quinaprilat was not readily dialyzable. Only 5.4% of the administered quinapril dose was recovered as quinaprilat during a single hemodialysis treatment. In view of these results, supplemental quinapril doses need not be routinely given to patients following hemodialysis. Overall, quinapril and quinaprilat pharmacokinetics in patients with ESRD on chronic hemodialysis were not markedly different from those previously observed in patients with moderate to severe renal dysfunction (CLcr less than 29 mL/min) not yet requiring hemodialysis (RDND).

Adult↗
PubMed1990

Neuropsychological deficit in schizophrenic subtypes: paranoid, nonparanoid, and schizoaffective subgroups.

Schizophrenic patients were carefully diagnosed and screened for a history of neurological disorders. Diagnosis and subtyping was based on DSM-III-R criteria, using the Structured Clinical Interview for DSM-III-R, which was administered by trained interviewers and confirmed by a research psychiatrist. The schizophrenic patients were compared with an age-matched control group on an extensive battery of neuropsychological measures. The undifferentiated/disorganized schizophrenic patients were consistently the most impaired on a broad range of tasks. When the effect of symptom severity and drug level were statistically controlled (analysis of covariance), however, the magnitude and number of differences were substantially reduced. The perseverative error score from the Wisconsin Card Sort Test showed the greatest difference between the groups. However, the strongest and most consistent effects were observed in relation to symptom ratings. These data indicate the importance of controlling for medication and symptom severity, and suggest that current diagnostic classifications may not be the most useful factors for studies of the cognitive correlates of schizophrenia.

Adult↗
PubMed1990

Gender differences in schizophrenia on MRI brain scans.

There are many reports of clinical and biological gender differences in schizophrenia. Gender differences in structural brain abnormalities in schizophrenia have been reported on both computed tomographic (CT) and magnetic resonance imaging (MRI) scans. We present here a new MRI study of cerebral structures in schizophrenia. On the basis of previous findings, we hypothesized that schizophrenic males are more likely than females to show smaller brains and larger ventricles compared to their control counterparts. Our results indicated that the opposite was true: schizophrenic females, but not schizophrenic males, had smaller craniums and brains and larger lateral and third ventricles on MRI scans. The possible significance and implications of these data are discussed.

Adolescent↗
PubMed1990

Overview of quinapril, a new ACE inhibitor.

Quinapril has been extensively studied for efficacy and safety in patients with hypertension or congestive heart failure (CHF) in the United States and Europe. Thirty-nine clinical pharmacology studies involving 383 patients have been completed. Moreover, 12 controlled, multicenter clinical studies and 3 single-center studies involving 1,793 patients have been conducted in hypertension. Three hemodynamic trials, two of which included both acute and long-term phases, and one placebo-controlled, dose-response study have been conducted in 333 patients with CHF. An additional 519 patients who completed studies on comparative agents were started on quinapril at the initiation of six long-term, open-label trials, which extended for up to 3 years. Twelve of 15 hypertension trials evaluated quinapril as first-line monotherapy in 1,452 patients with hypertension. Comparative agents included placebo in five trials (524 patients), enalapril in three trials (339 patients), captopril in four trials (335 patients), and chlorthalidone in one trial (74 patients). A total of 510 patients received quinapril in addition to a diuretic in double-blind trials: 341 patients with moderate to severe hypertension participated in three trials, and 169 patients with CHF participated in one trial. Quinapril administered once daily (o.d.) was evaluated in four placebo-controlled studies and in two studies of o.d. vs. twice-daily doses. The safety of quinapril has been evaluated in almost 2,700 patients in controlled, double-blind studies or in open-label extensions, for a total of more than 1,600 patient-years of exposure to quinapril. More than one-half of all patients participated in long-term trials: 980 patients were studied for 1 year and 315 patients were studied for 2 years at the time of data analysis. Safety data are available for 451 older patients (aged greater than or equal to 65 years), and comparative safety data from other compounds in the controlled studies are available for 1,058 patients. Quinapril's efficacy is comparable to that of other angiotensin-converting enzyme (ACE) inhibitors, and it has a lower incidence of adverse events or withdrawals due to adverse events than has been associated with captopril or enalapril.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

The pharmacokinetics and pharmacodynamics of quinapril and quinaprilat in renal impairment.

1. The pharmacokinetics and pharmacodynamics of quinapril and its active metabolite quinaprilat were studied in 20 subjects with renal function varying from normal to severe renal failure, during the approach to and at steady-state, and for 72 h after cessation of quinapril 20 mg orally for 7 days. 2. The apparent oral plasma clearance of quinaprilat (dose of quinapril equivalent/AUC of quinaprilat) was directly related to creatinine clearance (CLCr). The predicted apparent oral clearance of quinaprilat was zero when CLCr was zero, suggesting minimal extrarenal elimination. 3. Peak and trough concentrations of quinaprilat, and its apparent elimination half-life, varied inversely with CLCr. 4. Trough concentrations of quinaprilat showed no accumulation between 2 and 7 days, even in severe renal impairment. 5. There was a weak relationship between the oral plasma clearance of quinapril and CLCr. 6. ACE inhibition was marked and prolonged in all subjects, with 50% inhibition at 2.7 +/- 1.9% ng ml-1 of quinaprilat. The time for which ACE inhibition was greater than 90% was related inversely to CLCr. 7. Aldosterone concentrations and plasma renin activity responded in a predictable way, but with no clear relationship To CLCr. 8. Atrial natriuretic peptide concentrations were not affected by quinapril administration. 9. Glomerular filtration rate, as measured by Tc99mDTPA clearance, was not affected by quinapril administration. 10. Blood pressure at steady-state decreased significantly in the subjects with hypertension. The changes in blood pressure were not related to renal function. 11. These results suggest that the dosage rate of quinapril may have to be altered in renal impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1990

Third and lateral ventricular volumes in schizophrenia: support for progressive enlargement of both structures.

Third and lateral ventricular enlargement exists in a subgroup of schizophrenic patients. It is unclear, however, whether these abnormalities consistently coexist in the same patients or represent distinct pathologies. Whether these changes are static or progressive in nature is also unresolved. Third and lateral ventricular volumes (magnetic resonance imaging, total volumes calculated on complete coronal series) were examined in controls (n = 20) and schizophrenic patients (n = 20). Third ventricular, but not lateral ventricular, volume was increased in patients. Ventricular intercorrelations differed significantly between patients and controls. Ventricular measures were more highly correlated in patients than in controls. Age was also significantly more positively correlated with ventricular measures in patients. Results replicate the finding of third ventricular enlargement in some schizophrenic patients. The high correlation between lateral and third ventricular size in schizophrenic patients suggests a pathologic process affecting both structures. Enlargement of both third and lateral ventricles may be more specific to schizophrenic patients than enlargement of either structure alone. The data also indirectly support progression of ventricular enlargement.

Adult↗
PubMed1989

Perinatal complications and genetic loading in schizophrenia: preliminary findings.

History of perinatal complications (PCs) and first degree family history (FH) of psychiatric illness were examined in groups of schizophrenic/schizoaffective (n = 21) and bipolar (n = 10) patients. PCs were significantly more frequent in the schizophrenic and schizoaffective patients than in bipolar patients. An inverse relationship was found between PCs and FH status, with FH-positive patients having significantly fewer PCs than the FH-negative group. This relationship persisted when the bipolar patients were excluded. Findings emphasize the etiological importance of genetics and perinatal events in the psychoses, and support the validity of a familial/sporadic distinction.

Brain Damage, Chronic↗
PubMed1989

Structural brain-imaging findings in affective disorders: an overview.

In recent years, numerous reports of structural brain abnormalities found with computerized tomography (CT) scans in affective disorders (e.g., major depression, bipolar disorder) have been published. More currently, magnetic resonance imaging (MRI) studies have provided additional data on brain structure in affective disorders. In this article, the various CT and MRI findings in affective disorders are reviewed, and the clinical and research relevance of those neuroanatomical findings are presented and discussed.

Brain↗
PubMed1989

Quinapril--a preclinical review of the pharmacology, pharmacokinetics, and toxicology.

Quinapril is an orally active, non-peptide, nonsulfhydryl angiotensin-converting enzyme (ACE) inhibitor that acts potently and specifically to interrupt the conversion of angiotensin I to angiotensin II in both plasma and tissue. Quinapril is enzymatically hydrolyzed to a pharmacologically active diacid form quinaprilat. Quinapril is efficacious in hypertensive models exhibiting both high (renal hypertensive rats, diuretic-treated dogs) and normal (spontaneously hypertensive rats) plasma renin activity. Quinapril does not prevent the development of hypertension when plasma renin activity (PRA) is markedly suppressed as in the deoxycorticosterone-saline treated rat. Hemodynamic studies in dogs indicate that quinapril decreases total peripheral and renal vascular resistance. Quinaprilat produces natriuresis and mild diuresis at doses that do not alter mean arterial blood pressure. Quinapril has the potential to affect plasma lipids beneficially or at least be "lipid neutral." Oral absorption of quinapril is rapid in rats, dogs, and monkeys. There is rapid and extensive distribution of radiolabel to most tissues except brain. Plasma radiolabel concentration-time profiles exhibit polyexponential decay with a prolonged terminal phase at low concentrations in all species. Metabolism to compounds other than quinaprilat is not extensive. Quinapril is excreted primarily as quinaprilat and to a lesser degree as quinapril. Quinapril is well tolerated in a variety of pharmacologic safety screens and its toxicity profile is similar to that of other ACE inhibitors. Quinapril does not adversely affect reproduction; it is not teratogenic, carcinogenic, or mutagenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

The clinical pharmacokinetics of quinapril.

Quinapril (Q) and quinaprilat (QT) pharmacokinetics are dose proportional following single oral 2.5- to 80-mg Q doses. Q absorption and hydrolysis to QT is rapid with peak Q and QT concentrations occurring one and two hours postdose, respectively. Peak plasma QT concentrations were approximately fourfold higher than those of Q (923 vs 207 ng/mL following 40-mg Q). Dose-proportional QT area under the curve and dose-independent percent of dose excreted in urine as QT demonstrate that the extent of Q conversion to QT is constant over the dose range studied. Q and QT were eliminated from plasma with apparent half-lives of 0.8 and 1.9 hours and apparent plasma clearances of 1,850 and 220 mL/min, respectively, over the 2.5- to 80-mg dose range. Following oral 14C-Q, 61% and 37% of radiolabel was recovered in urine and feces, respectively. Q plus QT accounted for 46% of radioactivity circulating in plasma and 56% of that excreted in urine. Metabolism to compounds other than QT is not extensive. Two diketopiperazine metabolites of Q have been identified in plasma and urine, with approximately 6% of an administered dose excreted in urine as each of these metabolites. Peak plasma concentrations of these metabolites are similar to that of Q, and each is eliminated rapidly with a half-life of approximately one hour. Urinary excretion profiles indicate the presence of other minor metabolites. In summary, the absorption of Q and conversion to QT is rapid and dose-proportional, subsequent clearance of both Q and QT is independent of dose, and metabolism to compounds other than QT is not extensive.

Absorption↗
PubMed1989

The pharmacokinetics of angiotensin converting enzyme inhibitors in patients with renal impairment.

The clearance of drugs excreted entirely unchanged by the kidneys is assumed to relate directly to renal function. The clearance of drugs which are entirely metabolized is usually not altered in patients with renal impairment, although there are examples of both increased and decreased metabolic clearance rates. The clearance of metabolites which are excreted unchanged through the kidneys is also directly related to renal function. The angiotensin converting enzyme (ACE) inhibitors enalapril, ramipril, cilazapril and quinapril are prodrugs that are rapidly converted to active metabolites which are excreted unchanged through the kidneys. Studies have consistently demonstrated reduction in the apparent oral clearance of the active metabolites, in proportion to the degree of impairment of renal function. In addition, for quinapril at least, the metabolic clearance of the parent drug is slightly reduced in renal impairment. The activity of captopril and lisinopril lies in the parent molecule itself. Lisinopril is excreted renally unchanged, while captopril is both metabolized and excreted renally unchanged. The duration of ACE inhibition after administration of any of the ACE inhibitors is prolonged in proportion to the degree of renal impairment. From these pharmacokinetic and pharmacodynamic properties, it follows that the dose rate of the ACE inhibitors should be reduced in direct proportion to the degree of reduction in renal function. Reducing the dose, rather than prolonging the dose interval, is more logical for compliance and for maintaining a consistent degree of ACE inhibition over 24 h.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Structural abnormalities in the frontal system in schizophrenia. A magnetic resonance imaging study.

Thirty-eight schizophrenics and 49 normal controls underwent magnetic resonance imaging. Midline sagittal cuts indicated that the schizophrenics had significantly smaller frontal lobes, as well as smaller cerebrums and craniums. The findings are consistent with some type of early developmental abnormality that might retard brain growth and therefore skull growth. These findings are confirmed on a smaller sample of patients on whom we have coronal cuts. Decreased cerebral and cranial size are associated with prominent negative symptoms, although decreased frontal size is not. Decreased cranial and cerebral size was also associated with impairment on some cognitive tests. These findings are consistent with the hypothesis that some schizophrenics may have a type of early developmental abnormality associated with prominent negative symptoms and cognitive impairment. Further, the results suggest that schizophrenics may have a type of structural frontal system impairment. Thus, they provide anatomic evidence for the "hypofrontality hypothesis."

Adult↗
PubMed1986

Cerebral ventricular enlargement in schizophrenia. A preliminary follow-up study.

Lateral cerebral ventricular enlargement is now known to occur in some schizophrenic patients. To determine whether ventriculomegaly in schizophrenia is a static vs progressive process, we conducted a follow-up computed tomographic brain scan study on 11 young male patients, three years after initial scans were obtained. No significant change was found in the mean ventricles-brain ratio of this small schizophrenic sample after three years. Four of 11 patients showed noticeable increases (greater than 50%) in individual ratio. Methodologic problems are discussed and the need for follow-up studies as a research strategy is emphasized.

Adult↗
PubMed1986

A controlled magnetic resonance imaging study of corpus callosum thickness in schizophrenia.

Two previous postmortem studies reported an increased thickness of the corpus callosum in schizophrenic patients compared to psychiatric controls. We report an in vivo study of the corpus callosum in schizophrenic patients (n = 38) and healthy controls (n = 41) using magnetic resonance (MR) brain imaging. A significant increase in mean callosal thickness was found in the middle and anterior, but not the posterior, parts of the callosal body. However, when the patients and controls were compared by gender and handedness, schizophrenic men were found not to differ from control men in callosal thickness, regardless of handedness, whereas schizophrenic women were found to have a highly significant increase in callosal middle and anterior thickness compared to control women. The data suggest that increased callosal thickness in schizophrenia is gender related, a factor that is not considered by postmortem studies. The implications of increased callosal dimensions in female schizophrenics are discussed.

Adult↗