Tetrahydrozoline, a derivative of imidazoline, is found in over-the-counter eye drops and nasal sprays. Other derivatives include naphazoline, oxymetazoline, and xylometazoline. Poisoning can result from an overdose. Tetrahydrozoline is an alpha agonist and its main mechanism of action is the constriction of conjunctival blood vessels. This serves to relieve the redness of the eye caused by minor ocular irritants. When used, “only as directed,” tetrahydrozoline is an effective medication which shrinks blood vessels thus alleviating reddened “bloodshot” eyes. If taken internally, however, this drug acts like a potent high blood pressure medicine. Symptoms reported in both children and adults who have swallowed some of these eye care products either by accident or via malicious activity include marked drowsiness, low blood pressure, slowed heart rate, and possibly even coma and impaired breathing. Quantities as low as ½ to 1½ teaspoonfuls (approximately 1/6 to ½ of a half ounce bottle) have caused pronounced reactions in small children. Toxic effects following tetrahydrozoline ingestion can be serious and at times require close observation and treatment in an intensive care setting. Fortunately, no deaths have been reported.

Affygility Solutions has an occupational exposure limit (OEL) and control band assignment for this active pharmaceutical ingredient (API).


CAS Registry Number:
Tetrahydrozoline, Tetrizolina, Tetryzolin
$597 USD


The OEL monograph for this compound is under development. Let us know if you'd like to be notified when this document becomes available.

Why do you need this OEL Fastrac monograph?

OEL Fastrac monographs are a cost-effective and convenient way to meet the requirements for PDEs (ADEs) contained in the EMA Guideline on setting health based exposure limits for use in risk identification in the manufacture of different medicinal products in shared facilities (EMA/CHMP/CVMP/SWP/169430/2012), and to obtain the following information:

  • The numerical OEL and control band assignment needed to determine the level of required engineering controls and personal protective equipment
  • A listing of all cited references utilized in the derivation of the OEL and ADE
  • An expert review and discussion with respect to the critical endpoints of concern, the rationale for the choice of endpoints, and dose that is to be used in the derivation of the ADE (PDE), as required by the EMA's Guideline on setting health-based exposure limits for use in risk identification in the manufacture of different medicinal products in shared facilities

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  • K. Rosenthal
  • Director of Manufacturing
  • Pharmatek Laboratories