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

(2) and (4)

(1) (2) (3)

(1) and (3)

All of the above.

(4) only