What is Prilocaine?
Prilocaine is an amino amide type of local anaesthetic with a fast onset of action. It is pharmacologically similar to lidocaine and both can be combined for topical application (Emla cream) prior to a dermal filler injection. Although both are equally safe and effective anaesthetics, prilocaine’s onset of action is slower than lidocaine. However, the former is excreted more rapidly and has lower cardiotoxicity. Lidocaine is widely used in the US, while European countries seem to prefer Prilocaine.
Mechanism of Action
Amide-type local anaesthetics like prilocaine and lidocaine relieve pain by interfering with nerve excitation and conduction. It works by blocking sodium (Na+) current through direct interaction with voltage-gated Na+ channels. The injectable form of prilocaine is often used in dentistry, while a combination of lidocaine and prilocaine is also formulated in topical preparation for dermal anaesthesia. It is rapidly metabolised in the liver and excreted in the urine.
Candidates for Treatment
Prilocaine is recommended for patients with cardiac problems, as well as renal and hepatic insufficiency. If large volumes of tumescent anaesthesia is required, a combination of prilocaine and lidocaine will increase effectiveness without heightened toxicity.
Because the metabolite (ortho-toluidine) of Prilocaine may cause methemoglobinemia, it is not intended for patients with such disorders, including other blood disorders: anemia, sickle cell anemia, porphyria in children, or symptomatic hypoxia. Avoid this anaesthetic in patients with known hypersensitivity to prilocaine, sulfites, parabens, and other amide-type anaesthetics.
Prilocaine Side Effects
Prilocaine was withdrawn from use in the US because it may induce methemoglobinemia, a disorder characterized with elevated levels of methemoglobin in the blood. Methemoglobin is a type of haemoglobin that can still carry oxygen but cannot effectively release it to body tissues. Following the occurrence of this adverse effect, cyanosis may occur in 2–3 hours. Methemoglobinemia from prilocaine use is dose-dependent, although still a rare occurrence; and is induced when a dosage of more than 600mg is given.
Side effects of using a topical prilocaine cream include:
- Burning or stinging;
- Sensitivity where the cream is applied;
Rare side effects can include:
- Irregular heartbeat;
- Severe drowsiness;
- Shallow breathing.