Most anaphylactic reactions to penicillin occur
1. when the drug is administered parenterally.
2. within minutes after drug administration.
3. in patients who have already experienced an allergic reaction to the drug.
4. in patients with a negative skin test to penicillin allergy.

All of the above.

(4) only

(2) and (4)

(1) and (3)

(1) (2) (3)