MUSCLE CRAMPS AND ELEVATED SERUM CREATINE-PHOSPHOKINASE LEVELS INDUCED BY BETA-ADRENOCEPTOR BLOCKERS

We have assessed the propensity of beta-adrenoceptor blockers to cause muscle cramps and to raise the serum creatine phosphokinase (CPK) lev el in 78 patients with essential hypertension. After a control period, a beta-adrenoceptor blocker without intrinsic sympathomimetic activit y (ISA; propranolol, metoprolol or arotinolol) was administered for th ree months. Thereafter, the patients were randomised to receive a beta -adrenoceptor blocker with ISA (pindolol or carteolol) for three month s or a beta-adrenoceptor blocker without ISA for a further three month s. This pattern was continued until all beta-adrenoceptor blockers had been given. At the end of each period, CPK and CPK-MB levels were mea sured. Of the 78 subjects, muscle cramps occurred in 27 during treatme nt with pindolol and 32 during treatment with carteolol. No complaints were made by subjects treated with propranolol and arotinolol, but mu scle cramps were reported in 2 treated with metoprolol. While muscle c ramps were caused both by pindolol and carteolol in 16 subjects, they were caused by either of these drugs in the remainder of the subjects. Muscle cramp occurred mainly in the calves when the patients were in bed at night. Serum CPK and CPK-MB levels increased significantly duri ng treatment with pindolol (control period vs pindolol, CPK = 96 vs 13 3 IU . ml(-1), CPK-MB=14 vs 18IU . ml(-1)) or carteolol (CPK = 117 . I U ml(-1), CPK-MB = 18 . IU ml(-1)) while the levels during treatment w ith propranolol, arotinolol and metoprolol did not change from those i n the control period. The change in serum CPK during treatment with ca rteolol or pindolol was significantly correlated with the control seru m CPK level. No correlation was observed between muscle cramps and ser um CPK level. There were individual differences in the severity of mus cle cramps, with some subjects complaining frequently of severe muscle cramps. Because muscle cramps are frequently experienced at night, th ey disturb sleep and lower the quality of life in patients. This probl em should be considered during treatment with beta-adrenoceptor blocke rs with ISA.