Which of the following are common adverse effects of local anesthetics?

Local anesthetics can indeed cause systemic toxicity and local tissue irritation, making this the most comprehensive and accurate response.

Systemic toxicity can arise if the anesthetic is inadvertently injected into a blood vessel or if a large dose is used, leading to high plasma concentrations. This may result in central nervous system symptoms such as dizziness, tinnitus, seizures, and in severe cases, respiratory depression or cardiovascular complications.

Local tissue irritation is also a common concern, as the local anesthetic can cause inflammation, pain, or hypersensitivity at the injection site. This irritation may be due to the chemical properties of the anesthetic, including its pH and the preservatives it contains.

While allergic reactions are indeed a potential adverse effect, they are relatively rare compared to systemic toxicity and local irritation. Other options, such as headaches, nausea, transient hypertension, and bradycardia, may occur but are not as directly associated with the action of local anesthetics as systemic toxicity and local tissue irritation are. Thus, systemic toxicity and local tissue irritation form a key part of understanding the full range of adverse effects associated with local anesthetics, making this answer appropriate and accurate.