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Biomedical subjects

D Maclean

Publications and source records attributed to D Maclean.

At least 55 records · Page 3Linked to original sources
PubMed1988

Aims of combination therapy--improved quality of life or better blood pressure control?

The combination of nifedipine and atenolol must be evaluated in terms of risks and benefits to the hypertensive patient. Disadvantages with single-agent therapy justify trials of combination regimens. beta-Blockers may be unacceptable to some patients because of gastrointestinal upset, musculoskeletal symptoms, tiredness, malaise, insomnia, depression or confusion, sweating, breathlessness or cold extremities. The side effect profile varies from patient to patient and between different beta-blockers. Calcium antagonists also have characteristic side effects, including severe headaches, flushing and oedema, tachycardia and possibly worrying palpitations, and polyuria. Combining a calcium antagonist and a beta-blocker can reduce some side effects; for example, tachycardia is offset by addition of beta-blocker to calcium antagonist therapy, and beta-blocker-induced cold extremities may be reversed with a drug such as nifedipine. Moreover, the antihypertensive efficacy is increased, which is useful in previously resistant patients. However, an excessive fall in blood pressure is a possible adverse effect of the combination. There is also the possibility of precipitating heart failure in patients with cardiomegaly and severely compromised left ventricular function. The combination of nifedipine and atenolol was evaluated in 25 patients in a randomised, crossover trial following a month's treatment with atenolol 50mg twice daily. Patients received either atenolol 50mg twice daily alone, or atenolol 50mg twice daily with sustained release nifedipine 20mg or 40mg twice daily, or placebo twice daily during three 4-week treatment periods. Additional antihypertensive benefit was obtained by addition of the low dose of nifedipine compared with atenolol alone, but no further advantage was obtained with the higher nifedipine dose.(ABSTRACT TRUNCATED AT 400 WORDS)

Atenolol↗
PubMed1988

Amlodipine and captopril in moderate-severe essential hypertension.

The therapeutic usefulness of adding once-daily amlodipine (10 mg) for four weeks in moderate-severe hypertensive patients uncontrolled on low dose captopril (25 mg twice daily) alone was studied in 29 patients in a double-blind, placebo-controlled two-way crossover comparison. Once daily amlodipine was shown to be an effective antihypertensive drug when combined with captopril. The amlodipine minus placebo differences in mean changes from captopril baseline values were: -18/-12 mmHg and -20/-12 mmHg for supine and standing systolic/diastolic pressures (P less than 0.001 for all four pressure variables). The combination was well tolerated, and no patient discontinued therapy. Five patients experienced ankle oedema and four patients reported flushing while receiving amlodipine/captopril.

Adolescent↗
PubMed1986

A comparison of response and production protocols for assessing perceived exertion.

Two cycle ergometer protocols for assessing perceived exertion were compared before and after a fatiguing run. In the response (R) protocol, the subject rated the perceived exertion (RPE) of a series of power outputs assigned by the investigator. In the production (P) protocol, the investigator selected the RPE values and the subject adjusted his power output using a hand-held control. The relationship between RPE and power output (the regression coefficient and the slope and intercept of the regression line) was the same for both protocols. Fatigue due to the run caused a small increase in RPE (average 1.5 units) at a given exercise intensity and a commensurate decrease in power output (average 19 W) for a given RPE. The P protocol is safer than the R protocol because it makes no assumptions with regard to the physical condition of the subject. It is superior to the R protocol because it is an interval scale. These advantages suggest that the P protocol should be used instead of, or at least in addition to, the more traditional R protocol.

Adult↗
PubMed1986

Future/novel uses of beta blockers in clinical therapeutics.

Beta-blocker usage in the United Kingdom centers around propranolol and oxprenolol as noncardioselective drugs, atenolol and metoprolol as cardioselective agents, and pindolol or oxprenolol when partial agonist activity is desired. Any meaningful comparison of a novel beta blocker against the established drugs must be a variable-dose trial, for the optimum dose of any beta blocker that can be tolerated varies widely. Effective beta blockade is considered to have been achieved when the standing heart rate has been lowered to about 55 beats/minute.

Adrenergic beta-Antagonists↗
PubMed1986

Felodipine compared to nifedipine as "third-line drug" in resistant hypertension.

Felodipine is a new dihydropyridine calcium antagonist, and in hypertension it is a much more effective "third-line" drug than hydralazine. Nifedipine, on the other hand, is the established dihydropyridine calcium antagonist that has been increasingly used to treat hypertension. Information is now needed on the relative merits and demerits of these two drugs. This study appraised, therefore, the therapeutic utility of twelve months' treatment with nifedipine 20-60 mg twice daily in 55 patients with previous drug-resistant hypertension who had been successfully treated for the previous year with felodipine 5-20 mg twice daily, each calcium antagonist being used in combination with atenolol 100 mg daily with or without chlorthalidone 25 mg daily. Initially, nifedipine maintained comparable blood pressure control to that which had been achieved by felodipine, although in the longer term (over eight months) nifedipine proved less effective than felodipine had (p less than 0.02) and more patients became uncontrolled (supine diastolic blood pressure, Phase V, greater than or equal to 90 mmHg) on the maximum tolerated dose of the calcium antagonist (chi 2 = 4.13, p less than 0.05 greater than 0.025). The former degree of blood pressure control was, however, reestablished by increasing the dose of nifedipine or reintroducing the diuretic as necessary, and this control was maintained over the next four months. Minor side effects were less common on nifedipine than they had been during the preceding felodipine treatment phase. Felodipine thus has more pronounced and sustained antihypertensive effects than nifedipine, though its side effect burden may appear to be greater.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Early and late remodeling of the left ventricle after acute myocardial infarction.

This report describes early and later structural changes that occur in infarcted and noninfarcted ventricular myocardium after coronary arterial ligation in the rat. Histologic analysis was conducted of hearts subjected to 2 days (n = 22) and 21 days (n = 22) of coronary arterial occlusion, or to a sham operation (n = 22). Lengths, circumferences and areas of the left ventricle, of infarcted myocardium and of noninfarcted myocardium were obtained by videoplanimetry. Although the left ventricular (LV) endocardial circumference was similarly increased at 2 days (19 +/- 3 mm, mean +/- standard deviation) and 21 days (20 +/- 3 mm) compared with shams (13 +/- 3 mm, p less than 0.01), LV epicardial circumference was similar in all 3 groups (30 +/- 2, 31 +/- 2 and 31 +/- 2 mm, respectively). The area enclosed by the endocardial circumference was significantly (p less than 0.01) increased at 2 days (20 +/- 6 mm2) and 21 days (22 +/- 6 mm2) compared with shams (7 +/- 4 mm2); however, the area enclosed by the epicardial circumference was similar at 2 days, 21 days and in shams (70 +/- 9, 72 +/- 9 and 73 +/- 10 mm2, respectively). The total LV tissue area was similar at 2 and 21 days, but was less than that in shams (p less than 0.01). Between 2 and 21 days, 3 measures of infarcted myocardium significantly decreased: its segments of endocardial and epicardial circumference, its circumference and its area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Topographic changes in the left ventricle after experimentally induced myocardial infarction in the rat.

The factors that determine the thickness of transmural myocardial infarcts are unknown. Therefore, the relation between the size and thickness of transmural infarcts in 67 rats 21 days after occlusion of the left main coronary artery was studied. On examination of histologic sections, infarct size was determined by planimetry and expressed as a percentage of the left ventricular (LV) area, and thickness was expressed as a percentage of noninfarcted ventricular septal wall thickness. The circumferential length of the infarcted ventricle was measured in millimeters, as well as the circumferential length of the noninfarcted ventricular septum. Septal wall thickness was similar in rats with transmural infarcts and in sham-operated rats. No significant correlation was observed between infarct size and thickness (r = 0.10) or between circumferential length of the infarct and infarct thickness (r = 0.17). However, large (greater than or equal to 20% of the left ventricle, n = 37) and small (less than 20% of the left ventricle, n = 30) infarcts which were similarly thin (37 +/- 1% and 34 +/- 2% of septal wall thickness, respectively) affected LV topography differently. Large infarcts resulted in a 23% greater loss of myocardium (p less than 0.001), greater expansion of the LV cavity (18 +/- 9 mm2 compared with 14 +/- 1 mm2 in small infarcts, p less than 0.005), and lengthening of the septal wall (7.2 +/- 1.1 mm and 6.7 +/- 1.0 mm in large and small infarcts, respectively [p less than 0.05], and 6.3 +/- 0.1 mm in shams). Increase in cavity area and septal length in infarcted ventricles suggested a volume overload hypertrophy, which at 3 weeks was nonetheless inadequate to provide as much normal muscle as was present in sham-operated rats. In an additional 9 rats with subendocardial infarctions (involving less than 75% of the LV wall from endocardium to epicardium), the LV walls were thicker (94 +/- 5% of septal wall thickness, compared with 35 +/- 1% for transmural infarcts, p less than 0.001) and an inverse correlation was observed between infarct size and thickness. In conclusion, neither the size of a transmural infarct in rat nor the circumferential length of infarction determines the thickness of the infarct; however, infarct size does affect LV topography by increasing LV cavity area and the length of the noninfarcted septal wall. Subendocardial infarcts result in less myocardial thinning than do transmural infarcts.

Animals↗
PubMed1983

Antithyroid effect of chlorpropamide?

1 The relationship between plasma chlorpropamide concentration and thyroid function was examined in 87 maturity onset diabetic patients receiving chronic therapy. 2 Although plasma chlorpropamide concentration was weakly negatively correlated with serum thyroxine (r = 0.33, P less than 0.01) the mean serum thyroxine and thyrotrophin (TSH) were not different from that of a matched control group of diabetics treated with diet alone. 3 Serum thyroxine was negatively correlated with the duration of diabetes in both groups. 4 These results suggest that chlorpropamide does not have a clinically significant antithyroid effect.

Adult↗
PubMed1983

A comparison of flurbiprofen and paracetamol in the treatment of primary dysmenorrhoea.

Twenty-five patients suffering from primary dysmenorrhoea took part in a double-blind crossover study which demonstrated flurbiprofen (100 mg three times a day) to be significantly more effective than paracetamol (1 g three times a day) in providing pain relief on Days 1 and 2, and on the worst day of pain. Flurbiprofen also appeared to reduce the incidence of secondary symptoms of nausea and feeling faint, and menstrual blood loss. The study was also analyzed as if a parallel group study and showed flurbiprofen to be significantly more effective than paracetamol.

Acetaminophen↗