Effects and plasma levels of propranolol and metoprolol in hyperthyroid patients

Abstract

The effects and plasma concentrations of different doses of propranolol and metoprolol were studied in 34 hyperthyroid patients. The initial daily doses were propranolol 160 mg or metoprolol 200 mg. If the resting heart rate remained above 75 beats per min after treatment for 4-7 days, the dose was increased and the patient re-examined after a further 4-7 days. Propranolol (n = 17) caused a reduced heart rate, a decrease in serum 3,3',5-triiodothyronine (T3) and an increase in serum 3,3',5'-triiodothyronine (reverse T3, rT3). In 10 patients, there was no change in T3 or rT3 until the daily dose of propranolol had been increased to 240 or 320 mg. The plasma level of propranolol was significantly correlated with the decrease in T3 and the increase in rT3. Metoprolol (n = 17) caused a reduction in heart rate similar to that following propranolol. However, serum T3 was only slightly reduced even after an increase in dose to 300 or 400 mg, and serum rT3 was not altered. Metoprolol concentrations were not significantly correlated with the fall in T3. It appears that the influence of beta-blockers on T4 conversion is of little importance for the clinical improvement in hyperthyroid patients, and rather it is a consequence of beta 1-adrenergic blockade interfering with the effect of T3. In addition, the findings support the assumption that therapeutic failure with beta-blockers in hyperthyroidism may be due to suboptimal treatment, and that individualized dosage is necessary.

Hypothalamic-Pituitary-Thyroid Axis Function in Women With a Menstrually Related Mood Disorder

“…Furthermore, we found that the low T4 concentrations and elevated T3/T4 ratios were associated with increased premenstrual symptom severity in the entire sample. Additional clinical relevance of increased T4 to T3 conversion that we found in MRMD women (22) and that Wang with colleagues have reported in PTSD (6,8) comes from the evidence that propranolol, a centrally acting beta-adrenergic receptor blocker, is widely used in treatment of thyrotoxicosis and is effective in reducing T3 concentrations (35). Animal studies have shown that propranolol decreases the expression of type II deiodinase, the enzyme involved in the conversion of T4 to T3 in central nervous system, consequentially leading to decreased conversion of T4 to T3 (1,2,36).…”

Influence of beta‐adrenoceptor blocking agents on lymphocyte function in vitro.

“…As for the clinical significance of the employed concentrations it may be noted that, during propranolol (320 mg daily) treatment of hyperthyroid patients, the drug concentrations in plasma were less than 1 ,zmol/l (Nilsson et al, 1980). In the present study the pronounced in vitro effects with propranolol were seen only at higher concentrations.…”

Effect of carteolol, indenolol and metoprolol on the thyroid hormone of hyperthyroid patients.

“…It was reported that propranolol has no direct effect on thyroid functions, as measured by radioiodine uptake and serum protein-bound-iodine (Wartofsky et al 1975). Several authors (Heyma et al 1980;Nilsson et al 1980) suggest that propranolol-induced changes in T3 and rT3 concentrations might be due to MSA (Heyma et al 1980) or direct inhibition of the enzyme responsible for the T4 monodeiodionation to T3 (Nilsson et al 1980). It is also possible that the changes might result from f32-adrenoreceptor blockade, since some authors have noticed a decrease in T3 during propranolol treatment, but no changes during the administration of selective f31-adrenoreceptor blockers such as atenolol (Nilsson et al 1979), practolol (Murchison et al 1976), and metoprolol (Murchison et al 1979; Nilsson et al TABLE 3.…”

“…Metoprolol had no effect on serum thyroid hormone levels. The decrease in the serum level of thyroid hormones by carteolol and indenolol but not by metoprolol in patients with hyperthyroidism would be due to the blockade of f2-adrenoreceptors concerning with thyroid hormone secretion.carteolol; indenolol ; metoprolol ; thyroid hormone ; hyperthyroidism Propranolol causes a fall in serum triiodothyronine (T3) concentration in hyperthyroid patients (Verhoeven et al 1977 ;Kallner et al 1978 ;Saunders et al 1978), probably by its action on peripheral conversion of thyroxine (T4) to T3 and reverse T3 (rT3) (Heyma et al 1980;Nilsson et al 1980), although f3-adrenoreceptor blockers other than propranolol were reported to have no effect on serum thyroid hormones (Murchison et al 1976;Wahlberg et al 1976;Nilsson et al 1979: Jones et al 1981. …”