The safety and effectiveness of prilocaine depend on proper dosage, correct technique, adequate
precautions, and readiness for emergencies. Standard textbooks should be consulted for specific techniques
and precautions for various regional anesthetic procedures. Resuscitative equipment, oxygen, and other
resuscitative drugs should be available for immediate use. (see WARNINGS and ADVERSE REACTIONS.)
The lowest dosage that results in effective anesthesia should be used to avoid high plasma levels and serious
adverse effects. Repeated doses of prilocaine may cause significant increases in blood levels with each
repeated dose because of slow accumulation of the drug or its metabolites. Tolerance to elevated blood levels
varies with the status of the patient. Debilitated, elderly patients, acutely ill patients, and children should be
given reduced doses commensurate with their age and physical status. Prilocaine should also be used with
caution in patients with severe shock or heart block.
Local anesthetic injections containing a vasoconstrictor should be used cautiously in areas of the body
supplied by end arteries or having otherwise compromised blood supply. Patients with peripheral vascular
disease and those with hypertensive vascular disease may exhibit exaggerated vasoconstrictor response.
Ischemic injury or necrosis may result. Preparations containing a vasoconstrictor should be used with caution
in patients during or following the administration of potent general anesthetic agents, since cardiac arrhythmias
may occur under such conditions.
Cardiovascular and respiratory (adequacy of ventilation) vital signs and the patient’s state of consciousness
should be monitored after each local anesthetic injection. Restlessness, anxiety, tinnitus, dizziness, blurred
vision, tremors, depression or drowsiness should alert the practitioner to the possibility of central nervous
system toxicity. Signs and symptoms of depressed cardiovascular function may commonly result from a
vasovagal reaction, particularly if the patient is in an upright position. (see ADVERSE REACTIONS,
Since amide-type local anesthetics are metabolized by the liver, prilocaine should be used with caution in
patients with hepatic disease.
Patients with severe hepatic disease, because of their inability to metabolize local anesthetics normally, are at
greater risk of developing toxic plasma concentrations. Prilocaine should also be used with caution in patients
with impaired cardiovascular function since they may be less able to compensate for functional changes
associated with the prolongation of A-V conduction produced by these drugs.
Many drugs used during the conduct of anesthesia are considered potential triggering agents for familial
malignant hyperthermia. Since is not known whether amide-type local anesthetics may trigger this reaction and
since the need for supplemental general anesthesia cannot be predicted in advance, it is suggested that a
standard protocol for the management of malignant hyperthermia should be available. Early unexplained signs
of tachycardia, tachypnea, labile blood pressure and metabolic acidosis may precede temperature elevation.
Successful outcome is dependent on early diagnosis, prompt discontinuance of the suspect triggering agent(s)
and institution of treatment, including oxygen therapy, indicated supportive measures and dantrolene (consult
dantrolene sodium intravenous package insert before using).
Prilocaine should be used with caution in persons with known drug sensitivities. Patients allergic to paraaminobenzoic
acid derivatives (procaine, tetracaine, benzocaine, etc.) have not shown cross sensitivity to
Use In The Head And Neck Area
Small doses of local anesthetics injected into the head and neck area,
including retrobulbar, dental and stellate ganglion blocks, may produce adverse reactions similar to systemic
toxicity seen with unintentional intravascular injections of larger doses. Confusion, convulsions, respiratory
depression and/or respiratory arrest, and cardiovascular stimulation or depression have been reported. These
reactions may be due to intra-arterial injection of the local anesthetic with retrograde flow to the cerebral
circulation. Patients receiving these blocks should have their circulation and respiration monitored and be
constantly observed. Resuscitative equipment and personnel for treating adverse reactions should be
immediately available. Dosage recommendations should not be exceeded. (see DOSAGE AND ADMINISTRATION.)
Carcinogenesis, Mutagenesis, Impairment Of Fertility
Studies of prilocaine in animals to evaluate the
carcinogenic and mutagenic potential or the effect on fertility have not been conducted.
Chronic oral toxicity studies of ortho-toluidine, a metabolite of prilocaine, in mice (150 to 4800 mg/kg) and rats
(150 to 800 mg/kg) have shown that ortho-toluidine is a carcinogen in both species. The lowest dose
corresponds to approximately 50 times the maximum amount of ortho-toluidine to which a 50 kg subject would
be expected to be exposed following a single injection (8 mg/kg) of prilocaine.
Ortho-toluidine (0.5 mg/mL) showed positive results in Escherichia coli DNA repair and phage-induction
assays. Urine concentrates from rats treated with ortho-toluidine (300 mg/kg, orally) were mutagenic for
Salmonella typhimurium with metabolic activation. Several other tests, including reverse mutations in five
different Salmonella typhimurium strains with or without metabolic activation and single strand breaks in DNA
of V79 Chinese hamster cells, were negative.
Use In Pregnancy
Pregnancy Category B
Reproduction studies have been performed
in rats at doses up to 30 times the human dose and revealed no evidence of impaired fertility or harm to the
fetus due to prilocaine. There are, however, no adequate and well-controlled studies in pregnant women.
Animal reproduction studies are not always predictive of human response. General consideration should be
given to this fact before administering prilocaine to women of childbearing potential, especially during early
pregnancy when maximum organogenesis takes place.
It is not known whether this drug is excreted in human milk. Because many drugs are
excreted in human milk, caution should be exercised when prilocaine is administered to a nursing woman.
Dosages in children should be reduced, commensurate with age, body weight, and physical
condition. (see DOSAGE AND ADMINISTRATION.)