The question asks about the reason why the β-adrenergic antagonist propranolol is prescribed to about 50% of manic patients receiving Lithium. Let's break down the problem:
Therefore, the correct answer is Tremor.
Choose the correct match of laxative and its Mechanism of Action (MOA):

Match the following:
(P) Schedule H
(Q) Schedule G
(R) Schedule P
(S) Schedule F2
Descriptions:
(I) Life period of drugs
(II) Drugs used under RMP
(III) List of Prescription Drugs
(IV) Standards for surgical dressing