Indications
Metriphonate (also called metrifonate or trichlorfon) is an organophosphate antiparasitic medicine. Products sold under this name are generally veterinary and are used in animals, not people. Uses include:
- Treating external parasites such as lice, mites, ticks and fly larvae (maggots and warble flies) in cattle, sheep, goats and other livestock
- Treating some worm infections of the gut in animals
- Controlling parasites such as fish lice and flukes in fish ponds, as directed
It was once used in people for a type of schistosomiasis (bilharzia), but this use has largely been replaced by safer medicines.
How It Works
Metriphonate is changed into a substance that blocks the enzyme cholinesterase in parasites. This enzyme normally switches off nerve signals. When it is blocked, the parasite’s nerves and muscles stop working properly, and it is paralysed and dies.
Dosage and Administration
Dose depends on the animal species, body weight, the parasite and the method (pour-on, spray, dip, oral or water treatment). Use exactly as directed on the label or by a veterinarian. Measure carefully, because the margin between an effective and a toxic dose is narrow.
Interactions
- Do not use together with, or within a few days of, other organophosphate or carbamate insecticides or wormers, as poisoning risk increases.
- Muscle relaxants such as Suxamethonium and some other medicines can have stronger effects in treated animals.
- Tell the veterinarian about all other treatments.
Contraindications
- Very young, weak, sick or stressed animals, unless a veterinarian advises
- Animals recently treated with other cholinesterase-blocking products
- Not for human use
Side Effects
In animals, signs of too much effect include drooling, watery eyes, diarrhoea, frequent urination, muscle trembling, weakness, difficulty breathing and collapse. These need prompt veterinary care; Atropine is the usual antidote, given by a veterinarian.
For people handling the product: if it is swallowed, splashed in the eyes or spilled on the skin, wash at once and get urgent medical help for headache, blurred vision, sweating, drooling, vomiting, stomach cramps, muscle twitching, chest tightness or difficulty breathing.
Pregnancy and Lactation
Use in pregnant animals only on veterinary advice. Pregnant or breastfeeding women should avoid handling the product. Follow the milk and meat withdrawal times stated on the label before using milk or sending animals for slaughter.
Precautions and Warnings
- For animal use only. Not for human use.
- Wear gloves and protective clothing; do not eat, drink or smoke while handling.
- Keep away from food and animal feed, and do not contaminate ponds or water sources except as directed.
- Observe withdrawal periods.
- Store and dispose of containers safely.
Overdose
Overdose causes organophosphate poisoning (see Side Effects). This is an emergency for animals and people. Contact a veterinarian, or for human exposure go to the nearest hospital immediately and take the pack with you.
Therapeutic Class
Veterinary antiparasitic, organophosphate (cholinesterase inhibitor).
Storage
Store below 30°C in a dry place, away from light, in the original container, away from food and feed, and out of the reach of children and animals.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.