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Neurolytic agent

Phenol

Phenol is a neurolytic agent used in pain medicine for chemical neurolysis, typically in the management of severe spasticity or intractable cancer-related pain.

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: 2–3 mL of oily phenol 5% injection into the submucosal layer at the base of the haemorrhoid
Route: Submucosal injection
Frequency: Several sites may be injected at one session; repeat as clinically indicated
Max: Maximum total 10 mL at any one time
Indication in this SPC is haemorrhoid sclerotherapy (Oily Phenol Injection 5% w/v). For submucosal injection ONLY — not for intrathecal use; take care to avoid accidental intravenous injection. Injection too close to the anal verge may cause severe pain. Contraindicated in children and neonates. openFDA cross-check returned a topical OTC product (not equivalent).

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.

Contraindications

  • Hypersensitivity to phenol, to nuts, in particular almond oil, or to any component
  • Must not be used over large areas (sufficient absorption may cause toxic symptoms)
  • Contraindicated in neonates and children

Side effects

  • Injection-site pyrexia, pain, discomfort, irritation
  • Ulcer and tissue necrosis
  • Abscess formation, including prostatic abscess; necrotizing fasciitis; retroperitoneal sepsis (after misplaced injection)
  • Dizziness; hepatitis
  • Dysuria, urinary incontinence, impotence

Interactions

  • None stated

Clinical monograph

How it works

It produces non-selective protein denaturation and destruction of nerve tissue, interrupting transmission along the targeted nerve.

Prescribing in practice

  • It causes irreversible, non-selective tissue destruction, so injection must be precisely targeted by an experienced operator to avoid damage to motor fibres, vasculature and surrounding structures.
  • It is concentration- and solvent-dependent and is used only for selected neurolytic indications after careful patient selection, often following a diagnostic local-anaesthetic block.
  • It is corrosive and toxic if absorbed systemically or applied to skin and mucosa, requiring careful handling and containment.

Monitoring

Patients should be monitored for the intended block effect and for adverse effects such as dysaesthesia, motor weakness or local tissue injury after the procedure.

Counselling the patient

  • Explain that neurolysis is intended to be long-lasting and that altered sensation or weakness in the area may occur.
  • Report new or worsening pain, numbness or weakness after the procedure.

Evidence & guidelines

Use is supported by established pain-medicine and palliative-care practice for neurolytic procedures in carefully selected patients.

Reference: FPM; 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).