Generally speaking, as the right party, longing an option does not require an additional margin. However, in terms of account risk, longing an option is equivalent to converting part of your available funds into a non-collateralized option contract of equal value. As a result, the net assets in your account remain unchanged, but the funds available are reduced.
It can be approximated as follows: available funds = net assets - initial margin. The increased margin actually represents a decrease in available funds, similar in principle to when you buy non-collateralizable stock (margin rate of 100%).