Amide local anaesthetic Pregnancy: Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity; as a precautionary measure it is preferable to avoid prilocaine hydrochloride during early pregnancy. Neonatal methaemoglobinaemia has been reported after paracervical (PCB) or pudendal block in the obstetric patient. Foetal adverse effects such as foetal bradycardia seem most apparent in paracervical block anaesthesia. Breast-feeding: prilocaine enters breast milk but no effects have been shown in breastfed newborns/infants of treated mothers.

Prilocaine hydrochloride

Brand names: Citanest

Prilocaine hydrochloride is an amide local anaesthetic used for infiltration anaesthesia and regional nerve blocks, including intravenous regional anaesthesia (Bier's block).

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: No fixed adult regimen is stated: the dose is adjusted according to the response of the patient and the site of administration, and the lowest concentration and smallest dose producing the required effect should be given. The SPC states only a ceiling — the maximum dose of prilocaine hydrochloride for healthy adults should not exceed 400 mg.

Route: Injection for local/regional anaesthesia (fetched product: Prilocaine hydrochloride 1% Solution for Injection). Careful aspiration before and during the injection is recommended to avoid intravascular injection.

Frequency: Per procedure, titrated to response — no repeat interval or daily frequency is stated in the source

Max: 400 mg for healthy adults (must not be exceeded). Elderly or debilitated patients require smaller doses, commensurate with age and physical status.

Preservative-containing solutions (multi-dose vials) should not be used for intrathecal or epidural anaesthesia, intraocular or retrobulbar injections, or in doses of more than 15 ml for other types of blockade. There have been post-marketing reports of chondrolysis in patients receiving post-operative intra-articular continuous infusion of local anaesthetics — prilocaine hydrochloride is not approved for this indication. Methaemoglobinaemia may occur at lower doses in patients with anaemia, congenital or acquired haemoglobinopathy, or on concomitant therapy known to cause it (e.g. sulphonamides); infants are particularly susceptible. Possibly porphyrinogenic — only prescribe in acute porphyria when no safer alternative is available. §4.5 was not present in the fetched eMC bundle (interactions below are taken from §4.4 and, where marked, from the US label). The openFDA cross-check label is 'Citanest Plain' 4% dental injection (72 mg/1.8 mL, 40 mg/mL), a different product and indication: it gives maximum recommended doses within a two-hour period of 4 mg/lb (8 mg/kg) for adults under 70 kg and 600 mg (15 mL, 8 cartridges) for adults 70 kg or more — these US dental figures differ from the UK 400 mg ceiling and were NOT merged into the dose above.

Paediatric dose

Dose: 5 mg/kg

Route: Injection for local/regional anaesthesia (1% solution for injection)

Frequency: Per procedure — no repeat interval is stated in the source

Max: Up to 5 mg/kg (children above the age of 6 months)

SPC §4.2 states: 'In children above the age of 6 months the dosage can be calculated on a weight basis up to 5 mg/kg.' Prilocaine hydrochloride should NOT be used in children under 6 months of age, nor for paracervical (PCB) block or pudendal block in the obstetric patient — there is an increased risk of methaemoglobin formation in children and in the neonate after delivery. Infants are particularly susceptible to methaemoglobinaemia due to lower activity of the reducing enzyme. Verify against a children's formulary and local protocol before use.

Dose adjustments

Renal

No numeric adjustment stated. §4.4: use cautiously in patients with liver or kidney damage if the dose or site of administration is likely to result in high blood levels; also in the elderly, patients in poor health, epilepsy, severe or untreated hypertension, impaired cardiac conduction, severe heart disease and impaired respiratory function.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance, to anaesthetics of the amide type, or to any of the excipients
Hypersensitivity to methyl and/or propyl parahydroxybenzoate (methyl-/propyl paraben) or to their metabolite para-aminobenzoic acid (PABA); paraben-containing prilocaine formulations should be avoided in patients allergic to ester local anaesthetics or to PABA
Avoid in patients with anaemia or congenital or acquired methaemoglobinaemia

Side effects

Hypotension (very common; more frequent after epidural blocks) and nausea (very common); vomiting and hypertension (common)
Paraesthesia and dizziness (common); signs and symptoms of CNS toxicity (uncommon) — circumoral paraesthesia, numbness of the tongue, light-headedness, hyperacusis, tinnitus, visual disturbances, dysarthria, muscular twitching or tremors preceding generalised convulsions
Bradycardia (common); cardiac arrest and cardiac arrhythmias (rare)
Methaemoglobinaemia and cyanosis (rare)
Allergic reactions including urticaria, oedema, dyspnoea, and anaphylactic reactions (rare); neuropathy and peripheral nerve injury (rare); respiratory depression (frequency not known)

Interactions

Class III anti-arrhythmic drugs (e.g. amiodarone) — patients should be under close surveillance and ECG monitoring considered, since cardiac effects may be additive (§4.4)
Drugs known to cause methaemoglobinaemia, e.g. sulphonamides — methaemoglobinaemia may occur at lower doses of prilocaine in patients receiving such concomitant therapy (§4.4)
US label: increased risk of methaemoglobinaemia with nitrates/nitrites, other local anaesthetics, antineoplastics (cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase), antibiotics (dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides), antimalarials (chloroquine, primaquine), anticonvulsants (phenobarbital, phenytoin, sodium valproate), and acetaminophen/paracetamol, metoclopramide, quinine, sulfasalazine
US label: concurrent vasopressor drugs and ergot-type oxytocic drugs may cause severe, persistent hypertension or cerebrovascular accidents
Full eMC §4.5 was not retrieved in this source bundle

Clinical monograph

How it works

It reversibly blocks voltage-gated sodium channels on nerve membranes, preventing depolarisation and propagation of the nerve impulse to produce local anaesthesia.

Prescribing in practice

Excessive doses can cause methaemoglobinaemia (a metabolite oxidises haemoglobin), presenting as cyanosis unresponsive to oxygen, and it should be avoided in those with congenital or acquired methaemoglobinaemia and used cautiously in anaemia or significant cardiorespiratory disease.
Inadvertent intravascular injection or overdose can cause systemic local anaesthetic toxicity, with CNS effects and cardiovascular depression, so use the lowest effective dose and aspirate before injecting.
Use with caution in hepatic impairment, where metabolism is reduced, and in the elderly and debilitated.

Monitoring

Monitor for signs of systemic toxicity and for cyanosis suggesting methaemoglobinaemia during and after administration.

Counselling the patient

Explain that numbness will develop in the area and wears off gradually, and to protect the numb area from injury.
Report any drowsiness, dizziness, tingling around the mouth or unusual blue discolouration of the lips or skin.

Evidence & guidelines

Prilocaine has a recognised association with methaemoglobinaemia at higher doses, and management with intravenous methylene blue is well established for clinically significant cases.

Reference: AAGBI safe practice; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Mepivacaine hydrochloride · Amide local anaesthetic

Pathways