Instillido (Lidocaine Hydrochloride)

• Instillido, a lidocaine‑based local anesthetic administered via the urethral route, is used to achieve temporary loss of sensation for specific urological procedures.
• Diagnostic urethroscopy: provides analgesia to allow comfortable visual examination of the urethral lumen.
• Therapeutic urethral surgery (e.g., urethrotomy): enables pain‑free manipulation of tissues during corrective interventions.
• Urethral catheter placement: reduces discomfort during insertion of catheters for short‑term drainage.

• Lidocaine hydrochloride blocks voltage‑gated sodium channels on neuronal membranes, stabilizing the inactive state of the channel and preventing depolarization. By inhibiting the influx of sodium ions, it halts the generation and propagation of nerve impulses, resulting in reversible loss of sensory perception in the area where it is applied. The effect is concentration‑dependent and typically begins within minutes, lasting for the duration of the procedure.

Lidocaine administered urethrally may be associated with local and systemic adverse reactions.

Common Side Effects

• Burning or stinging sensation at the application site
• Mild transient urethral irritation
• Temporary urinary urgency or frequency
• Mild headache

Serious or Rare Side Effects

• Allergic reaction (rash, angioedema, anaphylaxis)
• Systemic toxicity manifesting as seizures or CNS depression
• Cardiac arrhythmias or hypotension
• Methemoglobinemia (rare)

When using Instillido, several precautions should be observed to minimize risk and ensure safe administration.

• Allergy assessment: confirm no known hypersensitivity to lidocaine or amide‑type anesthetics.
• Dose limitation: use the lowest effective volume to achieve anesthesia.
• Cardiac monitoring: observe patients with pre‑existing conduction disorders for arrhythmias.
• Renal/hepatic impairment: adjust use and monitor for prolonged systemic exposure.
• Pregnancy and lactation: evaluate risk‑benefit ratio before administration.
• Store at room temperature: keep in original container, protect from moisture and direct sunlight.

Lidocaine can interact with other medications, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Class I antiarrhythmics (e.g., quinidine, procainamide): may potentiate cardiotoxic effects.
• Concurrent use of other local anesthetics: increases risk of systemic toxicity.
• CYP1A2 or CYP3A4 inhibitors (e.g., cimetidine, erythromycin): can raise plasma lidocaine levels.

Moderate Interactions (Monitor Closely)

• Beta‑blockers: may enhance bradycardia when systemic absorption occurs.
• Diuretics (e.g., furosemide): may reduce plasma protein binding, increasing free lidocaine.
• Central nervous system depressants (e.g., benzodiazepines, opioids): may augment sedation if systemic levels rise.