The results show that both drugs were highly effective
antihypertensive agents at rest and during exercise at
2 and 24 h post dose. The control of blood pressure
and heart rate was significantly better at 2 h than at 24
h with both drugs. Most patients were considered
satisfactorily controlled at 24 h at rest, but exercise
revealed significant loss of f3-adrenoceptor blockade
and blood pressure control. Exercise tolerance was
only reduced by 1% at 2 h and not significantly
reduced at 24 h, indicating a minimal effect of cardioselective
/8-adrenoceptor blockade on exercise tolerance.
The results show few differences between the two
drugs. Atenolol produced slightly lower blood
pressures overall but this only reached statistical
significance for exercise systolic pressures at 2 h postdose.
This is not unexpected as the peak plasma concentration
of atenolol occurs at 2 h (McAinsh, 1977)
compared to 3.5-4 h for metoprolol SA (Johnsson et
al., 1980). However, the peak exercise heart rates
were also significantly lower with atenolol at 24 h post
dose which may indicate a slightly lower degree of
13-adrenoceptor blockade with metoprolol SA at 24 h
compared to atenolol.
Atenolol 100 mg and metoprolol SA are both effective
and well tolerated hypotenisive drugs which taken
once daily can control resting blood pressure and
heart rate. Neither drug is however as effective at 24 h
as at 2 h post dose, especially in controlling the hypertensive
response to exercise.
We should like to thank Astra Cardiovascular for their
financial support. C.A.M. is supported by the British Heart
Foundation.