TETRAHYDROPYRIMIDINES Flashcards
SUBSTANCES
- Pyrantel Citrate, Tartrate salt: Bo, Eq, Fe, Ca, & Sus Pamoate /Embonate/ salt: Horses, Dogs and Cats
- Morantel (The methyl ester analog of pyrantel): Ruminants
- (Oxantel) dogs (in combinations)
MECHANISM OF ACTION
Cholinomimetic activity, ganglion-stimulant, interaction with parasitic nerve transmission, leading to spastic paralysis.
ANTHELMINTIC SPECTRUM
Antinematodal effect (Relatively large spectrum against GI nematodes – were 1st broad spectrum agents against these parasites)
• Adult gut worms & larval stages that dwell in the lumen/mucosal surface.
• Limited or no activity against migrating larvae, & Trichuris spp. (whipworms), except Oxantel
• Nematodes resistant to levamisole are cross-resistant to morantel due to the similarities of their mechanisms of action.
• Horses Anoplocephala perfoliata (tapeworm/cestode!)
PHARMACOKINETIC FEATURES
- Pyrantel tartrate (or citrate) is well absorbed by Sus & Ca, less well by Ru.
- The pamoate salt poorly soluble in water=>reduced absorption from the gut & allows the drug to reach and effect parasites in the large intestine, which makes it useful in Eq, Fe and Ca. (+ less negative-effects)
- Pyrantel metab is rapid=> metabolites excreted rapidly in the urine (40% of the dose in dogs); some unchanged drug is excreted in the faeces (principally in ruminants). Blood levels usually peak 4-6 hr post PO admin.
- Morantel is absorbed rapidly from the upper small intestine of Ov + metabolized rapidly in the liver; ~17% of the initial dose is excreted in the urine as metabolites within 96 hr after dosing (WPs for meat + milk are short /frequently 0 days for milk/).
SIDE-EFFECTS (Overdos.)
Cholinergic-types of signs. /Antidote: Atropine/ Morantel in Ruminants tends to be safer and more effective than Pyrantel.
APPLICATION
- Pyrantel pamoate: Horses 19, Dogs and Cats 14.4, mg/kg B.W. PO paste (+ in combinations tablets – see later)
- Morantel: Cattle Slow release ruminal bolus, Sheep Oral susp.
