Write SQL query to solve given problem: Among the patients who have been using Penicillin V Potassium 250 MG, what percentage of patients are female?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(CASE WHEN T1.gender = 'F' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.patient) FROM patients AS T1 INNER JOIN medications AS T2 ON T1.patient = T2.PATIENT WHERE T2.DESCRIPTION = 'Penicillin V Potassium 250 MG'