Synera Patch (lidocaine/tetracaine): Side Effects & Warnings

Generic drug: lidocaine and tetracaine

Brand name: Synera

What is Synera (lidocaine and tetracaine), and how does it work?

Synera (lidocaine 70 mg and tetracaine 70 mg) Topical Patch contains a local anesthetic used on intact skin to provide local dermal analgesia for superficial venous access and superficial dermatological procedures such as excision, electrodessication and shave biopsy of skin lesions.

What are the side effects of Synera?

Common side effects of Synera include localized site reactions such as hives, blanching, swelling, abnormal sensation, rash, or skin discoloration. Systemic side effects of Synera are uncommon but may include:

dizziness
headache
nausea
drowsiness
vomiting
lightheadedness
nervousness
apprehension
euphoria
confusion
ringing in the ears
blurred or double vision
sensations of heat or cold
numbness
twitching
tremors
convulsions
unconsciousness
respiratory depression and arrest

What is the dosage for Synera?

Synera should only be applied to intact skin. Use immediately after opening the pouch.

For adults and children 3 years of age and older:

Venipuncture or Intravenous Cannulation: Prior to venipuncture or intravenous cannulation, apply
Synera to intact skin for 20 to 30 minutes.
Superficial Dermatological Procedures: For superficial dermatological procedures such as superficial excision or shave biopsy, apply
Synera to intact skin for 30 minutes prior to the procedure.

While efficacy has not been established for children less than 3 years of age, safe use of
Synera in infants 4 to 6 months of age was documented in one study.

Simultaneous or sequential application of multiple
Synera patches is not recommended. However, application of one additional patch at a new location to facilitate venous access is acceptable after a failed attempt.

When Synera is used concomitantly with other products containing local anesthetic agents, the amount absorbed from all formulations should be considered, as local anesthetics are thought to have at least additive toxicities. If irritation or a burning sensation occurs during application, remove the patch.

What drugs interact with Synera?

Drugs That May Cause Methemoglobinemia When Used With Synera

Patients who are administered local anesthetics are at increased risk of developing methemoglobinemia when concurrently exposed to the following drugs, which could include other local anesthetics:

Examples Of Drugs Associated With Methemoglobinemia:

ClassExamplesNitrates/Nitritesnitric oxide, nitroglycerin, nitroprusside, nitrous oxideLocal anestheticsarticaine, benzocaine, bupivacaine, lidocaine, mepivacaine, prilocaine, procaine, ropivacaine, tetracaineAntineoplastic agentscyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicaseAntibioticsdapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamidesAntimalarialschloroquine, primaquineAnticonvulsantsphenobarbital, phenytoin, sodium valproateOther drugsacetaminophen, metoclopramide, quinine, sulfasalazine

Antiarrhythmic Drugs

Synera should be used with caution in patients receiving Class I antiarrhythmic drugs (such as tocainide and mexiletine) since the systemic toxic effects are thought to be additive and potentially synergistic with lidocaine and tetracaine.

Local Anesthetics

When Synera is used concomitantly with other products containing local anesthetic agents, the amount absorbed from all formulations should be considered since the systemic toxic effects are thought to be additive and potentially synergistic with lidocaine and tetracaine.

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Is Synera safe to use while pregnant or breastfeeding?

There are no available data on Synera use in pregnant women to determine a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes.
Available data from an epidemiologic study and case series with parenteral lidocaine use in pregnant women have not identified a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes.
Published data on tetracaine use in pregnant women are not sufficient to determine any drug-associated risks.
The amount of lidocaine and tetracaine systemically absorbed from Synera is low compared to the parenteral route of administration and is not expected to result in significant fetal exposure.
Systemic exposure of Synera is directly related to both the duration of application and the surface area over which it is applied.
There are no data on the presence of tetracaine in human milk, the effects on the breastfed infant, or the effect on milk production.
Published studies on parenterally administered lidocaine have reported the presence of lidocaine in human milk with milk: plasma ratios ranging between 0.4 to 1.1. Available data on lidocaine’s effects on the breastfed child have not revealed a consistent pattern of associated adverse effects.
The amount of lidocaine present in human milk following topical administration is unknown, but systemic absorption from topical lidocaine is low.