Drug Class Description

Generic Name

Drug Description

Presentation

Indications

Adult Dosage

Care should be taken to prevent toxic reactions by avoiding intravascular injection. Careful aspiration before and during the injection is recommended. When a large dose is to be injected, e.g. in epidural block, a test dose of 3-5 ml of prilocaine containing adrenaline is recommended. An accidental intravascular injection may be recognised by a temporary increase in heart rate. The main dose should be injected slowly, at a rate of 100-200 mg/min, or in incremental doses, while keeping in constant verbal contact with the patient. If toxic symptoms occur, the injection should be stopped immediately.

The dose is adjusted according to the response of the patient and the site of administration.

The lowest concentration and smallest dose producing the required effect should be given.

The maximum dose of Citanest for healthy adults should not exceed 400mg.

Elderly or debilitated patients require smaller doses, commensurate with age and physical status.

In children above the age of 6 months the dosage can be calculated on a weight basis up to 5mg/kg.

Prilocaine for injection is not recommended in children under 6 months of age and for use in paracervical (PCB) block and pudendal block in the obstetric patient. There is an increased risk of methaemoglobin formation in children and in the neonate after delivery.

Child Dosage

Contra Indications

Known hypersensitivity to anaesthetics of the amide type or to any component of the solution.

Citanest should be avoided in patients with anaemia or congenital or acquired methaemoglobinaemia

Special Precautions

Regional or local anaesthetic procedures, except those of the most trivial nature, should always be performed in a properly equipped and staffed area, with the equipment and drugs necessary for monitoring an emergency resuscitation immediately available. When performing major blocks, an i.v. cannula should be inserted before the local anaesthetic is injected. Clinicians should have received adequate and appropriate training in the procedure to be performed and should be familiar with the diagnosis and treatment of side effects, systemic toxicity or other complications.

Great caution must be exercised to avoid accidental intravascular injection of this compound, since it may give rise to the rapid onset of toxicity, with marked restlessness, twitching, or convulsions, followed by coma with apnoea and cardiovascular collapse.

In common with other local anaesthetics, Citanest should be used cautiously in the elderly, patients in poor health, patients with epilepsy, severe or untreated hypertension, impaired cardiac conduction, severe heart disease, impaired respiratory function, and in patients with liver or kidney damage, if the dose or site of administration is likely to result in high blood levels.

Certain local anaesthetic procedures may be associated with serious adverse reactions, regardless of the local anaesthetic drug used, e.g:

- Central nerve blocks may cause cardiovascular depression, especially in the presence of hypovolaemia. Epidural anaesthesia should be used with caution in patients with impaired cardiovascular function.

- Retrobulbar injections may rarely reach the cranial subarachnoid space causing serious / severe reactions, including cardiovascular collapse, apnoea, convulsions and temporary blindness.

- Retro- and peribulbar injections of local anaesthetics carry a low risk of persistent ocular muscle dysfunction. The primary causes include trauma and/or local toxic effects on muscles and/or nerves.

The severity of such tissue reactions is related to the degree of trauma, the concentration of the local anaesthetic and the duration of exposure of the tissue to the local anaesthetic. For this reason, as with all local anaesthetics, the lowest effective concentration and dose of local anaesthetic should be used.

- Injections in the head and neck regions may be made inadvertently into an artery, causing cerebral symptoms even at low doses.

- Paracervical block can sometimes cause fetal bradycardia/tachycardia, and careful monitoring of the foetal heart rate is necessary

Epidural anaesthesia may lead to hypotension and bradycardia. This risk can be reduced either by preloading the circulation with crystalloidal or colloidal solutions. Hypotension should be treated promptly with e.g. ephedrine 5-10 mg intravenously and repeated as necessary.

To reduce the risk of dangerous side effects, children below the age of 6 months require special attention due to the risk of methaemoglobinaemia. Paracervical block (PCB) or pudendal block in the obstetric patient may lead to methaemoglobinaemia in the neonate.

Local anaesthetics should be avoided when there is inflammation at the site of the proposed injection.

Interactions

Drugs which may predispose to methaemoglobin formation, e.g. sulfonamides (eg cotrimoxazole), antimalarials and certain nitric compounds, could potentiate this adverse effect of prilocaine.

Prilocaine should be used with caution in patients receiving other local anaesthetics or agents structurally related to amide-type anaesthetics, since the toxic effects are additive.

Adverse Reactions

In common with other local anaesthetics, adverse reactions to Citanest are extremely rare and are usually the result of excessively high blood concentrations due to inadvertent intravascular injection, excessive dosage, rapid absorption or occasionally to hypersensitivity, idiosyncrasy or diminished tolerance on the part of the patient. In such circumstances systemic effects occur involving the central nervous system and/or the cardiovascular system.

CNS reactions are excitatory and/or depressant and may be characterised by nervousness, dizziness, blurred vision and tremors, followed by drowsiness, convulsions, unconsciousness and possibly respiratory arrest. The excitatory reactions may be very brief or may not occur at all, in which case the first manifestations of toxicity may be drowsiness, merging into unconsciousness and respiratory arrest.

Cardiovascular reactions are depressant and may be characterised by hypotension, myocardial depression, bradycardia and possibly cardiac arrest.

Allergic reactions to local anaesthetics of the amide type are extremely rare. They may be characterised by cutaneous lesions, urticaria, oedema or anaphylactoid reactions. However, other constituents of the solutions, e.g. methylparahydroxybenzoate, may cause this type of reaction. Detection of sensitivity by skin testing is of doubtful value.

Neurological complications for example nerve trauma, neuropathy, anterior spinal artery occlusion, arachnoiditis etc., have been associated with regional anaesthetic techniques, regardless of the local anaesthetic drug used.

Hypotension may occur as a physiological response to central nerve blocks.

This product gives rise to methaemoglobinaemia in a dose related fashion.

Clinically significant levels occur with cyanosis when doses of prilocaine exceed 600mg.

Methaemoglobinaemia may occur at lower doses of prilocaine in patients suffering from anaemia, from congenital or acquired haemoglobinopathy (including methaemoglobinaemia), or in patients receiving concomitant therapy e.g. sulphonamides, known to cause such conditions. Infants are particularly susceptible, due to a lower activity of the enzyme which reduces methaemoglobin to haemoglobin. Hence prilocaine is not recommended for paracervical block (PCB) or pudendal block in the obstetric patient and in children under the age of 6 months.

Methaemoglobinaemia may be treated by the intravenous administration of a 1% solution of methylene blue in a dose of 1mg/kg, over a 5 minute period.

Even low concentrations of methaemoglobin may interfere with pulse oximetry readings, indicating a false low oxygen saturation.

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