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ANTIHYPERTENSIVE THERAPY IN THE ELDERLY
200 of isolates showing demonstrated positivity by preceding by intranasal instillation into weaned, white Swiss mice. Mortality of 80-100% ensued in 4-7 days routinely. Confirmation of the cause of death was obtained by direct observation of amoeba in the harvested brain tissues and by prolific growth of the recovered organisms in Chang’s medium which is selective for
fluoresced
at
lower titres.
Pathogenicity
the
tests was
pathogenic Ncegleria. These studies which resulted in the first isolation of pathoin Florida from thermally polluted and freshwater lakes appear to indicate that thermal pollution of waters in Florida plays a minor role in the maintenance of pathogenic Naegleria in nature. Freshwater lakes from which isolates were obtained have been used for water sports by thousands of people each year and only seven fatalities due to pathogenic Ncegleria infections have been recorded, the first being in 1962. We suggest that other factors, probably host related, play a much greater role in the development of primary amoebic meningo-encephalitis in man than does the mere presence of the organisms in the water.
If beta-receptor blocking agents are used in the elderly because of ischaemic heart-disease it is important to start with a small dose because otherwise severe postural hypotension may occur, as I learnt to my cost when starting treatment of an elderly general practitioner who was also a personal friend. Whittington Hospital,
genic Ncegleria
’this research was sponsored in part by grants R-803511 and R-804375 from the Environmental Protection Agency and in part by the State of Florida, Department of Health and Rehabilitative Services. T7 ",, ’V’_"h’F. M. WELLINGS Office of Laboratory Services, Health and Rehabilitative Services, Tampa, Florida 33614, U.S.A.
Department of
A. L. LEWIS P. T. AMUSO
U.S. Environmental Protection Agency,
E. MONTUSCHI
London N19 5NF
MECHANISM OF PRAZOSIN COLLAPSE
SIR,-Severe hypotension and collapse may follow the use prazosin.1Since prazosin is thought to work by direct relaxation of arterial smooth musclesevere cardiovascular
of
side-effects would not be expected; such side-effects are not commonly associated with the clinical use of direct vasodilating agents such as hydrallazine or diazoxide. While using an in-vitro technique to study human arterial responses, we have observed effects of prazosin which may explain some of its sideeffects. Spiral strips of operative specimens of uterine, splenic and ileocolic arteries ("visceral arteries") and post-mortem specimens of palmar digital arteries ("peripheral arteries") were suspended at 37°C and the force developed at increasing concentrations of noradrenaline was measured. Prazosin in therapeutic concentrations4 had different effects on the dose-response curves to noradrenaline in the arteries of the two vascular beds studied (see figure).
Epidemiology Branch, Field Studies Division, Health Effects Research Laboratory,
S. L. CHANG
Cincinnati, Ohio 45268.
1. 2. 3. 4.
Gabriel, R. G., Meek, D., Ghosh, B. D. Lancet, 1975, i, 1095. Bendall, M. J., Baloch, K. H., Wilson, P. R. Br. med. J. 1975, ii, 727. Constantine, J. W. in Prazosin (edited by D. W. K. Cotton); p. 16. Amsterdam, 1974. Wood, A. J. J. clin. exp. Physiol. Pharmac. 1975, 2, 446.
ANTIHYPERTENSIVE THERAPY IN THE ELDERLY
SIR,-Dr Jackson and his colleagues4 rightly condemn the of
starting antihypertensive therapy after only one of blood-pressure. They are also justified in criticising the choice of therapy in the six cases they report. The repeated reference to "symptomless" hypertension, however, may be misleading. Surely it is now generally accepted that the reasons for lowering the blood-pressure in hypertensive patients have little to do with symptoms.’ One could also dispute the proposition that treatment of hypertension in the over-sixties is not worthwhile because it fails to reduce mortality.6 The main benefit of antihypertensive therapy is prevention of 7 practice
measurement
stroke.’
While debate will continue about the meaning of words such "elderly" and "hypertension", the prospect of disabling hemiparesis in the final years of life should be considered by any physician in deciding whether or not to treat the elderly as
hypertensive. Department of Internal Medicine, University of Cincinnati Medical Center, Cincinnati, Ohio 45267, U.S.A.
,
MARTIN FAIRMAN
SIR,-Dr Jackson and his colleagues4 rightly make the point that antihypertensive treatment in the elderly may be simply meddlesome medicine. However, they do not clearly enough make the point that elderly patients may be especially sensitive to
antihypertensive drugs, at least at the beginning although this is mentioned in the discussion.
of
treat-
ment,
3. Butt, C. G. New Engl. Med. 1966, 274, 1476. 4. Jackson, G., Piercianowoki, T. A., Mahon, W., Condon, J. Lancet, 1976, ii, 1317. 5. Pickering, G. W., Hypertension Causes, Consequences and Management. Edinburgh, 1974. 6. Fry, J. Lancet, 1974, ii, 431. 7. Hamilton, M., Harpur, J., Beevers, D. G., Fairman, M. J., Postgrad. med.
J. 1973,49,905.
Noradrenaline dose-response The
curves were
calculated
curves.
as a
percentage of the standard contrac-
produced by 80 mmol/1 potassium chloride obtained in six isolated visceral arteries (A) and five isolated "peripheral arteries" (B) (see text). The curves were obtained in the absence of prazosin (1-·)or in the presence of prazosin 40 nmol/1 (0-0) or 80 nmoVl (A—BLB Each point represents the mean of the responses:i:s.E.M.. ture
fluoresced
at
lower titres.
Pathogenicity
the
tests was
pathogenic Ncegleria. These studies which resulted in the first isolation of pathoin Florida from thermally polluted and freshwater lakes appear to indicate that thermal pollution of waters in Florida plays a minor role in the maintenance of pathogenic Naegleria in nature. Freshwater lakes from which isolates were obtained have been used for water sports by thousands of people each year and only seven fatalities due to pathogenic Ncegleria infections have been recorded, the first being in 1962. We suggest that other factors, probably host related, play a much greater role in the development of primary amoebic meningo-encephalitis in man than does the mere presence of the organisms in the water.
If beta-receptor blocking agents are used in the elderly because of ischaemic heart-disease it is important to start with a small dose because otherwise severe postural hypotension may occur, as I learnt to my cost when starting treatment of an elderly general practitioner who was also a personal friend. Whittington Hospital,
genic Ncegleria
’this research was sponsored in part by grants R-803511 and R-804375 from the Environmental Protection Agency and in part by the State of Florida, Department of Health and Rehabilitative Services. T7 ",, ’V’_"h’F. M. WELLINGS Office of Laboratory Services, Health and Rehabilitative Services, Tampa, Florida 33614, U.S.A.
Department of
A. L. LEWIS P. T. AMUSO
U.S. Environmental Protection Agency,
E. MONTUSCHI
London N19 5NF
MECHANISM OF PRAZOSIN COLLAPSE
SIR,-Severe hypotension and collapse may follow the use prazosin.1Since prazosin is thought to work by direct relaxation of arterial smooth musclesevere cardiovascular
of
side-effects would not be expected; such side-effects are not commonly associated with the clinical use of direct vasodilating agents such as hydrallazine or diazoxide. While using an in-vitro technique to study human arterial responses, we have observed effects of prazosin which may explain some of its sideeffects. Spiral strips of operative specimens of uterine, splenic and ileocolic arteries ("visceral arteries") and post-mortem specimens of palmar digital arteries ("peripheral arteries") were suspended at 37°C and the force developed at increasing concentrations of noradrenaline was measured. Prazosin in therapeutic concentrations4 had different effects on the dose-response curves to noradrenaline in the arteries of the two vascular beds studied (see figure).
Epidemiology Branch, Field Studies Division, Health Effects Research Laboratory,
S. L. CHANG
Cincinnati, Ohio 45268.
1. 2. 3. 4.
Gabriel, R. G., Meek, D., Ghosh, B. D. Lancet, 1975, i, 1095. Bendall, M. J., Baloch, K. H., Wilson, P. R. Br. med. J. 1975, ii, 727. Constantine, J. W. in Prazosin (edited by D. W. K. Cotton); p. 16. Amsterdam, 1974. Wood, A. J. J. clin. exp. Physiol. Pharmac. 1975, 2, 446.
ANTIHYPERTENSIVE THERAPY IN THE ELDERLY
SIR,-Dr Jackson and his colleagues4 rightly condemn the of
starting antihypertensive therapy after only one of blood-pressure. They are also justified in criticising the choice of therapy in the six cases they report. The repeated reference to "symptomless" hypertension, however, may be misleading. Surely it is now generally accepted that the reasons for lowering the blood-pressure in hypertensive patients have little to do with symptoms.’ One could also dispute the proposition that treatment of hypertension in the over-sixties is not worthwhile because it fails to reduce mortality.6 The main benefit of antihypertensive therapy is prevention of 7 practice
measurement
stroke.’
While debate will continue about the meaning of words such "elderly" and "hypertension", the prospect of disabling hemiparesis in the final years of life should be considered by any physician in deciding whether or not to treat the elderly as
hypertensive. Department of Internal Medicine, University of Cincinnati Medical Center, Cincinnati, Ohio 45267, U.S.A.
,
MARTIN FAIRMAN
SIR,-Dr Jackson and his colleagues4 rightly make the point that antihypertensive treatment in the elderly may be simply meddlesome medicine. However, they do not clearly enough make the point that elderly patients may be especially sensitive to
antihypertensive drugs, at least at the beginning although this is mentioned in the discussion.
of
treat-
ment,
3. Butt, C. G. New Engl. Med. 1966, 274, 1476. 4. Jackson, G., Piercianowoki, T. A., Mahon, W., Condon, J. Lancet, 1976, ii, 1317. 5. Pickering, G. W., Hypertension Causes, Consequences and Management. Edinburgh, 1974. 6. Fry, J. Lancet, 1974, ii, 431. 7. Hamilton, M., Harpur, J., Beevers, D. G., Fairman, M. J., Postgrad. med.
J. 1973,49,905.
Noradrenaline dose-response The
curves were
calculated
curves.
as a
percentage of the standard contrac-
produced by 80 mmol/1 potassium chloride obtained in six isolated visceral arteries (A) and five isolated "peripheral arteries" (B) (see text). The curves were obtained in the absence of prazosin (1-·)or in the presence of prazosin 40 nmol/1 (0-0) or 80 nmoVl (A—BLB Each point represents the mean of the responses:i:s.E.M.. ture