Biomedical subjects

Y W Lam

Publications and source records attributed to Y W Lam.

59 records · Page 4Linked to original sources

PubMed1988

Calcium metabolism, calcium-channel blocking agents, and hypertension management.

Increasing evidence has suggested that a disturbance of cellular calcium metabolism may have a role in initiating and maintaining elevated systemic vascular resistance in essential hypertension. Controversy exists over whether calcium can alleviate or exacerbate the hypertensive process, and diversity of calcium metabolism in hypertensive patients has been proposed. Calcium-channel blocking agents are potent vasodilators capable of correcting the elevated systemic vascular resistance. Clinical studies have shown that these drugs have antihypertensive efficacy comparable to established agents. The elderly, blacks, and patients with low renin activity respond well to calcium-channel blockers. These drugs may also offer potential advantages over established antihypertensive agents in patients with other coexisting diseases. Sustained release formulations have been developed, and initial experience with long-term efficacy and tolerability is encouraging. The calcium-channel blockers may become first-line therapy for treatment of hypertension in selected patients.

Calcium↗

PubMed1987

Sustained-release diltiazem compared with atenolol monotherapy for mild to moderate systemic hypertension.

The daily administration of 240 to 360 mg of diltiazem lowered blood pressure in a dose-related pattern similar to that seen in patients taking a daily dosage of 50 to 100 mg of atenolol. Sustained-release diltiazem was administered twice daily and atenolol once. Goal blood pressure was defined as less than 90 mm Hg or a reduction of greater than or equal to 10 mm Hg for patients with baseline pressures of 95 to 99 mm Hg in the supine position and was achieved in 60% of diltiazem-treated and 63% of atenolol-treated patients. The mean diltiazem dosage at the end of the study was 329 mg daily; for atenolol it was 80 mg daily. Adverse reactions considered possibly or probably drug related were reported by 26% of diltiazem patients and 38% of atenolol patients. Although both drugs were associated with a slower heart rate, atenolol patients showed a significantly greater negative chronotropic effect. Diltiazem, in a sustained-release form taken twice daily, is as effective as atenolol as a sole antihypertensive agent. It has a favorable side-effect profile and may be a useful alternative antihypertensive medication compared with existing beta-blocker therapy with atenolol.

Atenolol↗

PubMed1986

The clinical utility of a published nomogram to predict aminoglycoside nephrotoxicity.

Moore and colleagues recently published a nomogram for predicting the risk of aminoglycoside nephrotoxicity. This study was undertaken to evaluate the clinical usefulness of this nomogram. The nephrotoxicity risk scores of 61 patients were determined using parameters suggested by Moore et al. Thirteen patients (21%) could not be scored because their initial creatinine clearances exceeded the upper limit of the nomogram. Six patients (9.8%) developed nephrotoxicity (defined as a greater than or equal to 50% decrease in creatinine clearance). In five of these patients in whom risk scores could be determined, the scores were estimated at 14% or less. Twenty patients had risk scores of 10% or more (four patients, greater than or equal to 50%) without developing nephrotoxicity. These results demonstrate that this nomogram may have limited clinical application in predicting patients likely to develop aminoglycoside nephrotoxicity.

Adolescent↗

PubMed1986

Calcium channel blockers and treatment of hypertension.

Over the past years, research efforts have been focused on the pathophysiologic role of calcium ions, and the implication for the potential role of calcium channel blockers in the management of essential hypertension. Numerous studies have shown that nifedipine and verapamil are effective antihypertensive agents, initial experience with diltiazem is also encouraging. The magnitude of blood pressure reduction with these drugs is related to the pre-treatment blood pressure. In refractory hypertension, combination with other antihypertensive agents provide additive effect. In the elderly population and in patients with ischemic heart disease, supraventricular arrhythmia, bronchospastic disease, peripheral vascular disease or diabetes mellitus, the calcium channel blockers offer potential advantages over other antihypertensive agents. Experimental studies also suggest that these drugs may reverse ventricular hypertrophy. When long-term safety with these drugs is documented from well-controlled clinical trials, the calcium channel blockers may be our first line of therapy for the management of hypertension.

Antihypertensive Agents↗

PubMedDate not supplied

Rapid formation of clozapine in guinea-pigs and man following clozapine-N-oxide administration.

Clozapine and its metabolite clozapine-N-oxide (0.5 mg/kg) were administered intraperitoneally to guinea-pigs. Significant amounts of clozapine were detected in plasma, liver, frontal cortex and caudate after clozapine-N-oxide administration. The amount of clozapine detected in plasma two hours post-administration of N-oxide was approximately 40% of the amount of clozapine after clozapine injection. Tissue concentrations of clozapine in liver, frontal cortex and caudate were greater than plasma concentrations. Clozapine concentrations were almost equivalent in the liver. Clozapine concentrations after N-oxide injection were approximately 40-50% lower compared to clozapine concentrations after clozapine administration in the frontal cortex and caudate. A single dose of clozapine-N-oxide was given to a schizophrenic patient. Clozapine plasma concentrations were detected after N-oxide administration. This study shows that clozapine is formed from its N-oxide metabolite and that a reversible metabolic pathway exists for clozapine and clozapine-N-oxide.

Animals↗