Final answer:
Phenylephrine injection is not effective when injected into the corpora cavernosa. It is typically administered intravenously to increase blood pressure in certain situations.
Step-by-step explanation:
Phenylephrine injection is commonly used for various medical purposes. However, when it comes to injecting 0.3-0.5mL of phenylephrine into the corpora cavernosa, it is not an effective treatment option. Phenylephrine is typically administered intravenously to increase blood pressure in situations where cardiac function is compromised.