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Introduction- Hypertension and bipolar disorder are both very common clinical disorders. Lithium remains the mainstay of therapy of bipolar disorder and beta-blockers continue to be used frequently for hypertension. Co-administration of both the drug groups are a possibility and how they affect each other is valuable to know.

Method: Five groups of albino rabbits (n=10 each) were included in this study. One group fed with gum tragacanth served as control. Four groups were treated orally with lithium carbonate (50mg/kg), three groups out of them were co-administered with propranolol (15mg/kg), metoprolol (10mg/kg) & atenolol (10mg/kg) respectively. The blood drawn from the marginal ear vein of rabbits was used for estimation of serum lithium, sodium, and potassium levels by flame photometry. The effect of drug treatment on heart rate was recorded using a transducer connected to a polygraph machine.

Result: The administration of lithium to the rabbits caused an insignificant reduction in heart rate and in serum potassium concentration but raised serum sodium concentration (140.2±3.83 to 146.78±4.21). When propranolol was added the lithium concentration was found to be significantly raised from 0.47±0.02 to 0.63±0.06, and there was a marked reduction in the heart rate (246.56±6.69 to 206.3±8.98). The co-administration of lithium along with metoprolol & atenolol didn't show any significant change in either the heart rate, serum lithium or the sodium & potassium concentration.

Conclusion: It may be unsafe to co-administer lithium and beta-blockers. However in case of extreme necessity a cardioselective beta-blocker is to be preferred over a non-selective one.