IMIDAZOTHIAZOLES Flashcards
1
Q
SUBSTANCES
A
- Tetramisole, a racemic mixture (less safe, recently not used)
- Levamisole, L-isomer form (anthelmintic)
2
Q
MECHANISM OF ACTION
A
- As agonists at nicotinic acetylcholine receptors of nematodes they are ganglion-stimulant (cholinomimetic).
- They stimulate ganglion-like structures in somatic muscle cells of nematodes. This stimulation first results in sustained muscle contractions, followed by a neuromuscular depolarizing blockade resulting in paralysis.
3
Q
ANTHELMINTIC SPECTRUM
A
- Antinematodal; with broad spectrum of activity adulticidal (incl. Heartworm - D. immitis – potentional danger), larvacidal.
- They have no activity against hypobiotic larvae, flukes and tapeworms, and they are not ovicidal.
- Resistance to Levamisole has been reported frequently for GI nematodes of cattle and sheep. led to withdrawal of products
- Nematodes resistant to Levamisole are cross-resistant to Morantel (similar mechanism of action).
- Immunostimulant effects (5 days PO administration 2-5 mg/kg).
4
Q
PHARMACOKINETIC FEATURES
A
- The absorption and excretion is rapid, not affected by the route of administration or ruminal bypass. In cattle, peak blood levels <1 hr after SC administration.
- Concentrations decline rapidly; 90% of the total dose is excreted in 24 h., largely in the urine.
- Withholding periods for meat are short, and frequently there is no, or only a short withholding period for milk.
5
Q
SIDE-EFFECTS
A
- The therapeutic index (TI) is not as large for Levamisole (4-6). - Cats, Horses, and certain dog breeds (e.g. Kuvasz) are very sensitive, birds, reptiles are more tolerant. - Toxic signs are: cholinergic-type signs of salivation, muscle tremors, ataxia, urination, defecation, and collapse, asphyxia due to respiratory failure.
- Antidote: Atropine - Some transient inflammation at the site of SC injection.
6
Q
APPLICATION
A
Swine, 5-7.5; Dogs 5; Poultry, reptiles 10 mg/kg B.W. - Normally is administered PO (all species) or SC (sheep), and efficacy is generally considered equivalent with either route. - Topical preparations (pour on) for cattle have been developed.
