Pet Safety / Compounds / Ortho-phthalaldehyde (OPA / Cidex OPA)

Is Ortho-phthalaldehyde (OPA / Cidex OPA) safe for dogs and cats?

Low risk for pets

Unlikely exposure.

What is ortho-phthalaldehyde (opa / cidex opa)?

The IUPAC name is 1-[amino-(4-chloroanilino)methylidene]-2-propan-2-ylguanidine;hydrochloride.

Also known as: (1E)-1-[amino-(4-chloroanilino)methylidene]-2-propan-2-ylguanidine;hydrochloride, MFCD01732193, N1-(4-Chlorophenyl)-N5-isopropylbiguanide Hydrochloride, 1189671-34-8.

IUPAC name
1-[amino-(4-chloroanilino)methylidene]-2-propan-2-ylguanidine;hydrochloride
CAS number
643-79-8
Molecular formula
C8H6O2
Molecular weight
134.13 g/mol
SMILES
CC(C)N=C(N)N=C(N)NC1=CC=C(C=C1)Cl.Cl
PubChem CID
12498

Risk for dogs

Low risk

Unlikely exposure.

Risk for cats

Low risk

Unlikely exposure.

Regulatory consensus

3 regulatory and scientific bodies have classified Ortho-phthalaldehyde (OPA / Cidex OPA). The classifications differ — that's the data.

AgencyYearClassificationNotes
FDA—510(k) cleared high-level disinfectant for semi-critical medical devices
EU—Not currently approved under BPR — limited EU market presence
ACGIH—No TLV established yet. Manufacturer recommends 0.001 ppm ceiling based on sensitization potential

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where pets encounter ortho-phthalaldehyde (opa / cidex opa)

  • Healthcare — Endoscope reprocessing (Cidex OPA), Surgical instrument disinfection, Tonometer disinfection
  • Dental — Dental instrument high-level disinfection

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Ortho-phthalaldehyde (OPA / Cidex OPA):

  • Peracetic acid
    Trade-offs: Removes 95-99% of dissolved contaminants including metals, PFAS, nitrates; wastes 2-4 gallons per gallon produced (improving with newer systems); removes beneficial minerals; $0.05-0.25/gallon; requires pre-treatment for longevity.
    Relative cost: 1.2-2×
  • Hydrogen peroxide (vaporized)
    Trade-offs: Removes 95-99% of dissolved contaminants including metals, PFAS, nitrates; wastes 2-4 gallons per gallon produced (improving with newer systems); removes beneficial minerals; $0.05-0.25/gallon; requires pre-treatment for longevity.
    Relative cost: 1.2-2×

Frequently asked questions

Is ortho-phthalaldehyde (opa / cidex opa) safe for pets?

Unlikely exposure.

What products contain ortho-phthalaldehyde (opa / cidex opa)?

Ortho-phthalaldehyde (OPA / Cidex OPA) appears in: Endoscope reprocessing (Cidex OPA) (Healthcare); Surgical instrument disinfection (Healthcare); Dental instrument high-level disinfection (Dental).

Why do regulators disagree about ortho-phthalaldehyde (opa / cidex opa)?

Ortho-phthalaldehyde (OPA / Cidex OPA) has been classified by 3 agencies including FDA, EU, ACGIH, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Ortho-phthalaldehyde (OPA / Cidex OPA) in the pets app

Look up products containing ortho-phthalaldehyde (opa / cidex opa), compare to alternatives, and explore the full data record.

Open in pets View raw API data

Sources (1)
  1. — expert_curation

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →