Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

However, the adverse reaction information from clinical trials does provide a basis for identifying the adverse events that appear to be related to drug use and for approximating their incidence in clinical practice.

Lidocaine and tetracaine cream has been evaluated for safety in 2159 persons undergoing a superficial dermal procedure. Lidocaine and tetracaine cream was studied in 11 placebo-controlled and 1 active-controlled trials, and in open-label safety trials. All 2159 persons were exposed to only a single application of lidocaine and tetracaine cream.

Adverse reactions were assessed by collecting spontaneously reported adverse reactions, and observations made on formal evaluation of the skin for specific reactions.

Most common adverse reactions in clinical trials

Localized Reactions:In clinical studies, the most common local reactions were erythema (47%), skin discoloration (e.g., blanching, ecchymosis, and purpura) (16%), and edema (14%). There were no serious adverse reactions. However, one patient withdrew due to burning pain at the treatment site. 

Other Localized Reactions:The following dermal adverse reactions occurred in 1% or less of lidocaine and tetracaine cream-treated patients: ecchymosis, petechial rash, vesiculobullous rash, perifollicular erythema, perifollicular edema, pruritus, rash, maculopapular rash, dry skin, contact dermatitis, and acne. 

Systemic (Dose-Related) Reactions:Across all trials, 19 subjects experienced a systemic adverse reaction, 15 of whom were treated with lidocaine and tetracaine cream and 4 with placebo. The frequency of systemic adverse reactions was greater for the lidocaine and tetracaine cream group (1%) than the placebo group (0.3%). The most common systemic adverse events were headache, vomiting, dizziness, and fever, all of which occurred with a frequency of <1%. Other systemic reactions were syncope, nausea, confusion, dehydration, hyperventilation, hypotension, nervousness, paresthesia, pharyngitis, stupor, pallor, and sweating. 

Systemic adverse reactions of lidocaine and tetracaine are similar in nature to those observed with other amide and ester local anesthetic agents, including CNS excitation and/or depression (lightheadedness, nervousness, apprehension, euphoria, confusion, dizziness, drowsiness, tinnitus, blurred or double vision, vomiting, sensation of heat, cold or numbness, twitching, tremors, convulsions, unconsciousness, respiratory depression and arrest). Excitatory CNS reactions may be brief or not occur at all, in which case the first manifestation may be drowsiness merging into unconsciousness. Signs of CNS toxicity may start at plasma concentrations of lidocaine at 1000 ng/mL. The plasma concentrations at which tetracaine toxicity may occur are less well characterized; however, systemic toxicity with tetracaine is thought to occur with much lower plasma concentrations compared with lidocaine. The toxicity of co-administered local anesthetics is thought to be at least additive. Cardiovascular manifestations may include bradycardia, hypotension and cardiovascular collapse leading to arrest.