Final answer:
The intravenous route of administering penicillin should be avoided due to the high risk of sensitization and severe allergic reactions in predisposed individuals.
Step-by-step explanation:
Regarding penicillin sensitization, the route that produces the highest degree of sensitization and therefore should be avoided is the intravenous route. When penicillin is administered intravenously, the plasma levels achieved are substantially higher than those attained by oral or intramuscular administration. This can inadvertently increase the risk of sensitization and allergic reactions in individuals predisposed to Type I Hypersensitivities. Such hypersensitive reactions can occur almost immediately upon exposure to an allergen after prior sensitization and can be life-threatening, leading to anaphylactic shock or even a fatal coma in severe cases. Therefore, intravenous administration of penicillin in sensitive individuals is typically avoided, with other routes or alternative antibiotics being considered for treating infections.