Phenyltoloxamine

Warning

H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral]

P264, P264+P265, P270, P280, P301+P317, P302+P352, P305+P351+P338, P321, P330, P332+P317, P337+P317, P362+P364, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 4 reports by companies from 2 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Phenyltoloxamine

3.8

16.3

Phenyltoloxamine citrate is given in combination with acetaminophen in a tablet (ZFLEX). The dosage for adults 12 years and over is one-half or one tablet containing 500 mg acetaminophen and 55 mg phenyltoloxamine citrate every 4 hours.

Data used to generate the benchmarks include the following: Lowest Daily Dose (LDD): 165 mg/day, Lowest Therapeutic Dose (LTD): 2.1 mg/kg-day, and Screening Dose: 0.0007 mg/kg-day.

Readily accessible data regarding the protein binding of phenyltoloxamine is not available. In fact, many first-generation H1 antihistamines have never had their pharmacokinetics (ie. absorption, distribution, metabolism, and elimination) optimally investigated.

As a member of the first generation H1 antihistamines, it is known that phenyltoloxamine - like virtually all first generation H1 antihistamines - has a propensity for crossing the blood-brain barrier and acting on H1 histamine receptors there to interfere with neurotransmission. The most common results of this kind of first generation H1 antihistamine CNS neurotransmission interference are adverse effects like drowsiness, sedation, somnolence, and fatigue. Given these effects, under specific circumstances like a patient experiencing a pain or a cough that may be preoccupying all of their waking energy and attention, it is perhaps possible that the sedative and tranquilizing characteristics of phenyltoloxamine may be the factors that contribute to its apparent adjunctive analgesic and antitussive actions.

As a first-generation H1 antihistamine, phenyltoloxamine interferes with the agonist activity of histamine at the H1 receptor and are ostensibly used to attenuate inflammatory processes as a means to treat conditions like allergic rhinitis, allergic conjunctivitis, and urticaria. Reduction of the activity of the NF-kB (nuclear factor kappa-light-chain-enhancer of activated B cells) immune response transcription factor via the phospholipase C and phosphatidylinositol (PIP2) signaling pathways also serves to decrease antigen presentation and the expression of pro-inflammatory cytokines, cell adhesion molecules, and chemotactic factors. Moreover, lowering calcium ion concentration leads to increased mast cell stability which reduces further histamine release. Additionally, first-generation antihistamines like phenyltoloxamine readily cross the blood-brain barrier and cause sedation and other adverse central nervous system (CNS) effects, like nervousness and insomnia. By comparison, second-generation antihistamines are more selective for H1 receptors in the peripheral nervous system and do not cross the blood-brain barrier, resulting in fewer adverse drug effects overall. Furthermore, although some studies propose that phenyltoloxamine may possess some intrinsic antispasmodic and distinct local anesthetic properties, the specific mechanisms of action for these effects have not been formalized. Also, even though the combination of phenyltoloxamine's ability to cross the blood-brain barrier and cause various tranquilizing effects may explain to some extent how it may be able to potentiate analgesic effects, there are also studies that observed no potentiating effects associated with phenyltoloxamine use either.