Ectoparasiticides

Malathion Insecticide, relatively safe for mammals and birds because metabolized by other enzymes to inactive products some medical use as ectoparasiticide... 

The world market size for ectoparasiticides has been estimated to be US 400 million in 1981 with a projected real growth rate of 10-15% annually for the period 1981-1985. 

Pyrethroids, e.g. cypermethrin (89) and fenvalerate (90), are being employed. This class of compound is the result of structural manipulation by medicinal chemists of the naturally occurring pyrethrins (91) to overcome the latters photoinstability and lack of persistence when in use as ectoparasiticides. There are no heterocyclic representatives of this important class of insecticide/acaricide in use though many heterocyclic examples have appeared in the patent literature. 

Ectoparasiticides used to control flies, ticks and other skin parasites. These fall under the general heading of pesticides (section 1.2 above). 

Uses soil application of insecticide to control root flies, root worms and other soil insects in vegetables foliar application to control Colorado beetles on potatoes scale insects and mite eggs on citrus fruit stem borers and leafhoppers on rice, maize and sugar cane and white flies on cotton aside from control of mosquito larvae, it is also used as acaricide and animal ectoparasiticide. 

Ectoparasiticidal activities are also observed in some carbodiimides. The acetylcholinesterase activity of houseflies is inhibited by phosphotriesters obtained from diethyl phosphate and phenols using DCC. ... 

The global ectoparasiticide sales for 1998 were 1.35 billion (Figure 14). As we have noted earlier, the new flea control agents, fipronil, imidacloprid and lufenuron, command a substantial slice of this. Despite concerns about environmental and worker toxicity, organophosphates are still major products in the livestock sector. 

Table 17 Dosage forms and methods of application of topical ectoparasiticide preparations to individual species...

With regard to ectoparasiticides, public health and environmental concerns have led to the withdrawal of the organochlorines and organophos-phates in many countries. Since Elliot (1973) reported the first photostable synthetic pyrethroid, these compounds have both replaced the naturaUy occurring pyrethrins (extracted from chrysanthemum flowers) and progressively become the mainstay of external parasite control programs. 

Pyrethrins and synthetic pyrethroids are among the safest of the topically applied ectoparasiticides, because of their selective toxicity for insects (mam-malian-to-insect toxic dose ratio is greater than 1000, compared with 33 for organophosphates and 16 for carbamate insecticides). In contrast to the very wide margin of safety for mammalian species, pyrethroids are toxic to fish. The synergistic action of pyrethrins and piperonyl butoxide (in combination preparations) is due to the inhibition by piperonyl butoxide of the microsomal enzyme system of some arthropods. Preparations of synthetic pyrethroids (permethrin, cypermethrin) often contain a mixture of drug isomers in varying proportions. 

The classes of drug for which topical veterinary preparations are commercially available include ectoparasiticides, antibacterial agents, antifungal... 

---