FENTHION

Chemistry - A topical organophosphate antiparasiticide, fenthion occurs as a yellowish-brownalmost odorless, oily liquid. It is miscible with alcohol, but practically immiscible with water.

Storage, Stability, Compatibility

Follow storage and disposal directions as per each product'slabel. Do not mix with other agents.

Pharmacology - FENTHION

Fenthion is topically administered organophosphate. Organophosphates act byinhibiting acetylcholinesterase, thereby interfering with neuromuscular transmission of susceptibleparasites.Uses, Indications - In dogs, fenthion (Pro-Spot®) is indicated for the topical treatment of fleas. Incattle (non-lactating), fenthion is used in treating and controlling lice and cattle grub infestations. Inswine, it is used for the control of lice.

Pharmacokinetics - FENTHION

No information was located.

Contraindications, Precautions, Reproductive Safety

Do not use on dogs less than 10 weeksof age or on stressed, sick or convalescing animals. Fenthion's safety on breeding males or onpregnant females has not been established.
Do not treat calves less than 3 months old, or on stressed, sick or convalescing animals. Do notuse in lactating animals. Do not treat cattle within 10 days of dehorning, shipping, weaning, orexposure to contagious or infectious disease.

Adverse Effects, Warnings

In dogs, adverse effects reported after using Pro-Spot® includeanorexia, vomiting, loose stools/diarrhea, and intermittent coughing.
In cattle, fenthion may cause bloat, excessive salivation and posterior paralysis. The manufacturerstates that should such effects occur, it is highly probable that a host-parasite reaction exists. If ahost-parasite reaction occurs, the manufacturer recommends not using atropine (unless a grossoverdose) or stomach tubes to relieve bloat (trocarization may be useful). Anti-inflammatory agentsmay be useful.

Overdosage, Acute Toxicity

If overdoses occur, vomiting, tremors, hyperexcitability, salivationand diarrhea may occur. Cattle may present symptoms of frequent defecation, urination, salivation, muscular weakness or twitching. Use of succinylcholine, theophylline/aminophylline, reserpine, andrespiratory depressant drugs (e.g., narcotics, phenothiazines) should be avoided in patients withorganophosphate toxicity. Treatment of organophosphate toxicity may range from carefulobservation if symptoms are mild and not progressing, to treatment with atropine and pralidoxime.
Refer to those two monographs for more information on their use. If an ingestion or exposureoccurs in a human, contact a poison control center, physician or hospital emergency room.

Drug Interactions

Acepromazine or other phenothiazines should not be given within onemonth of using an organophosphate agent as their effects may be potentiated. Because of its anticholinesterase activity, avoid the use of organophosphates with DMSO. Fenthion could theoretically enhance the toxic effects of levamisole. Pyrantel Pamoate (or tartrate) adverse effects could be intensified if used concomitantly with an organophosphate. Patients using organophosphates should not receive succinylcholine or other depolarizing muscle relaxants for at least 48 hours. Drugs such as morphine, neostigmine, physostigmine and pyridostigmine should be avoided when using organophosphates as they can inhibit cholinesterase.