Product Name Closivet Solution for Injection for Cattle

SCIENTIFIC DISCUSSION

Product Name Closivet Solution for Injection for Cattle

MA Holder Norbrook Laboratories Limited

I. introduction

Closivet Solution for Injection for Cattle is authorised for use in cattle for the treatment of mixed trematode (fluke) and nematode or arthropod infestations due to gastrointestinal roundworms, lungworms, eyeworms, warbles, mites and lice of cattle. Specifically, the treatment is directed against the following: gastrointestinal roundworms, Ostertagia ostertagi (including inhibited larval stages), Ostertagia lyrata (adult), Haemonchus placei (adult and immature), Trichostrongylus axei (adult and immature), Trichostrongylus colubriformis (adult and immature), Cooperia oncophora (adult and immature), Cooperia punctata (adult and immature), Cooperia pectinata(adult and immature),Oesophagostomum radiatum (adult and immature), Nematodirus helvetianus (adult), Nematodirus spathiger(adult), Strongyloides papillosus(adult),Bunostomum phlebotomum (adult and immature), Toxocara vitulorum (adult), Trichuris spp.

Additionally, the product is to be used to treat lungworms, Dictyocaulus viviparus (adult and 4th stage larvae), liver fluke (trematodes), Fasciola gigantica, Fasciola hepatica. Treatment of fluke at 7 weeks (late immature), the efficacy is greater than 90%. Treatment of fluke at 12 weeks (mature), the efficacy is greater than 99%.

Closivet Solution for Injection for Cattle can also be used to treat eyeworms (Thelazia spp), parasitic stage cattle grubs, (Hypoderma bovis, Hypoderma lineatum), lice (Linognathus vituli, Haematopinus eurysternus, Solenopotes capillatus), andmange mites (Psoroptes ovis (syn P communis var bovis), Sarcoptes scabiei var bovis).

Closivet Solution for Injection for Cattle may also be used as an aid in the control of the biting louse Damalinia bovis and the mange mite Chorioptes bovis, but complete elimination may not occur.

The application was submitted in accordance with Article 13b of the Directive 2001/82/EC as amended by 2004/28/EC.

Closivet Solution for Injection for Cattle should be administered at a dosage rate of 200 g ivermectin per kg bodyweight and 5 mg closantel per kg bodyweight (1 ml per 25 kg). It should only be injected subcutaneously into the neck. A maximum dose of 10ml should be administered at any one site with any residual volume administered at another site in the neck. A sterile 16-gauge, one-inch needle is recommended.

It has been shown that the product can be safely used in the target species, although care should be taken when using the product in the vicinity of particular breeds of dog, (refer to SPC section 4.3). The slight reactions observed are indicated in the SPC.

II.QUALITY ASPECTS

Product Development and Composition

The active substances in Closivet Injection are ivermectin 5 mg/ml and closantel (as closantal dehydrate) 125 mg/ml, and the excipients are sodium formaldehyde sulphoxylate, povidone K12, polyethylene glycol and glycerol formal.

The product is sterilised by filtration. All holding vessels, equipment and rubber closures are sterilised by moist heat. Process validation data on the product have been presented in accordance with the relevant European guidelines.

Active Substance

Active substance 1

Ivermectin utilised in this product complies with the monograph in the European Pharmacopoeia (Ph. Eur) and conforms to a satisfactory Certificate of Suitability (CEP). The retest period for the active substance is 3 years when stored in polyethylene lined aluminium tins. No testing is required in addition to adherence to the monograph. A declaration has been provided by the active substance manufacturer which states that no substances of human or animal origin have been used in its manufacture.

Active substance 2

Closantel is presented as dehydrate of the sodium salt and complies with the monograph in the European Pharmacopoeia (Ph. Eur) and conforms to a satisfactory Certificate of Suitability (CEP).The applicant has provided a declaration of compliance with the directive concerning minimising the risk of transmission of spongiform encephalopathies via veterinary medicines. No starting materials of animal origin have been used in the manufacture of closantal sodium dihydrate.

Other Substances

The excipients are sodium formaldehyde sulphoxylate, povidone K12, polyethylene glycol and glycerol formal. All excipients except glycerol formal are monographed in the Ph.Eur.Glycerol formal does not have a pharmacopoeial monograph, an in-house specification was developed for this excipient. This is considered acceptable.

Packaging Materials

The containers for Closivet Injection are Type 1 glass multidose vials and aluminium caps complete with bromobutyl bungs and aluminium seals, enclosed in bottle protectors and are of a 100 ml, 250 ml and 500 ml size. The particulars of the containers and controls performed are provided and conform to the regulation.

Manufacture of the Finished Product

The product is manufactured fully in accordance with the principles of good manufacturing practice from a licensed manufacturing site. The applicant has provided details of the stages of, and method of manufacture. In process controls have also been described. Process validation data on the product have been presented in accordance with the relevant European guidelines. A format 3 TSE declaration states that no materials used in the finished product are relevant to the guideline on transmissible spongiform encephalopathies.Only materials of vegetable or synthetic origin are used in the manufacture of Closivet Solution for Injection for Cattle.

Finished Product Quality Control

The finished product is tested against the following parameters: appearance of product, container and closure, moisture, identity of active substances and impurities.

Stability of the Product

Active substance

A certificate of suitability (CEP) for ivermectin states a retest interval of three years when stored in polyethylene lined aluminium tins.

Satisfactory batch analysis data for six recent batches of closantal sodium dehydrate were also provided. This is considered acceptable.

Finished Product

Three batches made at a scale of 100L stored in amber glass containers and two batches made at a scale of 400L were subjected to testing under VICH[1] long term and accelerated conditions. Some sensitivity to light was detected with regard to ivermectin, thus it is recommended in the SPC that the product is protected from light and stored in the outer carton. The shelf-life of the finished product as packaged for sale is 18 months when stored at a temperature below 25°C.

In-Use

Data were provided on two batches of product made at a scale of 100 litres. An in-use shelf-life of 28 days is justified.

CONCLUSIONS ON QUALITY

The application was supported with regard to quality.

III. SAFETY ASPECTS

Pharmacology

The applicant provided bibliographical data which indicate that ivermectin uptake by parasites is mainly transcuticular. The varying effects of avermectins on various parasites are believed to be due to differences in membrane permeability to chloride ions. It is likely that parasiticidal action is mediated by interaction of avermectins with glutamate-gated ion channels in nematodes. Other studies implicate GABA[2] postsynaptic receptors, resulting eventually in membrane hyperpolarisation.

Closantel belongs to a class of compounds called salicylanilides, or proton ionophores. It is supposed that these ionophores act on the membrane of parasite mitochondria and ultimately prevent production of a proton gradient across the inner mitochondrial membrane.

The applicant also provided bibliographical data which show that ivermectin is only partially metabolised in cattle. 1% to 2% is excreted in the urine and the remainder in the faeces. Approximately 60% of ivermectin from cattle is unaltered in the dung, the remainder being excreted as metabolites or degradation products. Closantel is poorly metabolised and excreted 90% unchanged in the urine and faeces.

Toxicology

The applicant has provided bibliographical data which show that relevant toxicity issues have been addressed with regard to single and repeated dose toxicity, reproductive toxicity, mutagenicity, carcinogenicity, and other appropriate parameters.

Ivermectin

According to published literature, the LD50 for ivermectin, when delivered orally to mice is approximately 25 mg/kg, and in the dog, the LD50 is approximately 80 mg/kg. Much higher LD50s were observed following dermal administration.

Closantel

For closantel, an LD50 of between 331 mg/kg and 453 mg/kg has been seen in mice. This figure, (observed when closantel was given orally), was several times higher than the figure obtained by intramuscular delivery of closantel.

A study was performed by the applicant to check that toxicity of ivermectin and closantal is not increased when the two substances are administered together. In this study, ivermectin and closantel were co-administered to mice at 10 mg/kg bodyweight, and 250 mg/kg bodyweight, respectively. There was no mortality.

Repeated Dose Toxicity

For ivermectin, a NOEL[3] has been identified in a 90-day study as being 0.4 mg/kg/day in rats, and 0.5 mg/kg/day in dogs. For closantel, NOELs of 2.5 mg/kg/day in rats, and 2.5 mg/kg/day in dogs have been reported.

Reproductive Toxicity, including Teratogenicity

Reports of several studies on reproductive toxicity/teratogenicity were provided. For ivermectin, a multigeneration study in rats showed no effects on mating, fertility or pregnancy at doses up to 3.6 mg/kg/bodyweight/day. An increase in pup mortality was found to be due to the fact that ivermectin concentrates in milk. NOELs of 0.2, 5.0 and 1.5 mg/kg bodyweight for developmental toxicity were derived from studies in mice, rats and rabbits. Another study in dogs noted that there were no adverse effects in pups, where the drug was used at levels which did not cause maternal toxicity.

Studies in rats for closantel indicated no adverse effects at doses up to 100 mg/kg in single-generation studies, but some effect was seen on male fertility in multi-generation studies, (NOEL 10 mg/kg/bodyweight). No adverse effects on offspring were observed in developmental studies in rats and rabbits at doses up to 40 mg/kg/bodyweight.

Mutagenicity

Neither ivermectin nor closantel showed any mutagenic potential in a range of studies.

Carcinogenicity

Data from rodent studies, one on abamectin, (a compound structurally related to ivermectin), and two on closantel were provided.

Studies showed that abamectin was not carcinogenic to mice when given orally at 2.0 mg/kg/day for 105 weeks, with a NOEL of 1.5mg /kg/day, nor was abamectin carcinogenic to rats when given at 8 mg/kg/day over a period of approximately two years.

For closantel, data were presented which showed that in mice, up to 80 mg/kg was tolerated for 18 months. In the same study, it was found that in rats, where closantal was given orally at up to 40 mg/kg/day for 2 years, some haemopoietic tumours were seen at a dose rate of 10 mg/kg/day. This incidence was however, within the historical range. Spermatic granulomas were also observed. The NOEL for this study was 2.5 mg/kg/day.

In an additional study, data were presented on mice and rats which established that in general, no adverse effects were seen in doses up to 40 mg/kg/day over 24 months in rats, and 80 mg/kg/day over 18 months in mice. No differences were noted between treated groups and controls, except for a slight increase in mortality in mice.

Other Studies

The applicant provided bibliographical data for ivermectin on immunotoxicity, neurotoxicity, and the behavioural development of rats, and for closantel, neurotoxicity and physiological development in goat kids.

Details of two immunotoxicity studies were provided for ivermectin. No evidence was found of immunotoxic effects in repeat dose studies in rats, dogs and rhesus monkeys. In a second study, an immunostimulatory effect observed was a T-lymphocyte-macrophage-dependent antibody response in mice to sheep red blood cells. With regard to neurotoxicity and behavioural development in rats, published reports noted that ivermectin given during gestation at 1, 2 or 4 mg/kg from days 6-20 caused a variety of anomalies. Delayed eye opening was seen in pups at the 2 mg/kg dose, and the cliff avoidance reflex was altered in all treated groups. 2 mg/kg of ivermectin also altered the surface righting reflex, the development of locomotion, and turning ability. Swimming ability was also affected.

Closantel caused blindness in goat kids at very high doses. It was observed that there was an apparent reduction in the number of ganglionic neurones in the retina.

Observations in Humans

Ivermectin and closantel have been used in human medicine, and the applicant provided several published reports of the administration of both substances to humans. In the case of ivermectin, side effects were minimal, including sore throat, fever and headache. More serious effects in one study included pruritis, skin oedema, arthralgia and severe headache. In the case of closantel, side effects included nausea and vomiting following oral dosing, and tachycardia, sweating, micturition and defecation, reddening of the skin, nervousness, stress and a sense of anguish, on subcutaneous administration.

Residues

A GLP-compliant residues depletion study using the final formulation was conducted in cattle.

The product was administered topically in a single dose at a rate of 200 µg ivermectin and 5 mg closantel/kg/bodyweight to animals which were slaughtered at various time points.

Samples of edible tissues were taken from animals at several time points, and results showed that residues depleted to below the maximum residue limit (MRL) in all tissues before the end of the withdrawal period.

The analytical method was HPLC, and quantification was derived from measurement of a sample peak in comparison with a previously spiked sample. The method was fully validated. Residues of each active ingredient were below the MRLs for the relevant tissues in all samples collected before the authorised withdrawal period.

MRLs

Ivermectin / Closantel
MRL (µg/kg) / MRL (µg/kg)
Muscle / - / 1000
Liver / 100 / 1000
Kidney / 30 / 3000
Fat / 100 / 3000

Environmental Safety

This product required a Phase II environmental risk assessment. The predicted no effect concentration (PNEC) values derived from several studies were acceptable and in accordance with VICH guidelines.

It was noted that cattle are treated at pasture, and residues from ivermectin and closantel would reach the environment via excreta. Run-off of product subsequent to treatment was not considered to be a relevant route of exposure. The product if given to animals at pasture yields a PNECsoil initial value below 100 µg/kg, and the risk to plants and micro-organisms was considered acceptable.

Warnings and precautions as listed on the product literature are adequate to ensure safety to the environment when the product is used as directed. The product literature highlights the fact that the product is extremely dangerous to fish and aquatic life, and that care must be taken not to contaminate surface waters or ditches with the product or used container.

CONCLUSIONS ON SAFETY AND RESIDUES

Conclusions on User Safety

The applicant has provided a user risk assessment in compliance with the relevant guideline which describes potential exposure routes for the operator. The main exposure route is from spillage onto the skin, or accidental ingestion.

The following warnings and precautions as listed on the product literature and SPC are adequate to ensure safety to users of the product.

• Do not smoke, eat or drink while handling the product.
• Direct contact of the product with the skin should be kept to a minimum. Wash hands after use.
• Take care to avoid self-injection. Inadvertent self-injection may result in local irritation and/or pain at the injection site.

Conclusions on Consumer Safety

A withdrawal period of forty nine days was stipulated for meat and offal. The product is not to be used in cattle producing milk for human consumption, and is not to be used in non-lactating dairy cows including pregnant heifers within sixty days of calving.

The following statement is also included on the SPC:

Do not use any closantel-containing products during the 49 day withdrawal period. If an ivermectin-only product is used during this period, the withdrawal periods for all products must be observed.

Conclusions on Environmental Safety

Suitable data were presented which confirmed that Closivet Solution for Injection for Cattle is appropriate for use with regard to environmental safety.

IV. CLINICAL ASPECTS

Clinical Pharmacology

The two active substances in Closivet Solution for Injection for Cattle, ivermectin and closantel, both have well-established uses in veterinary medicine. The company provided a review of published literature on the pharmacodynamics and pharmacokinetics of the individual active substances, supplemented with reports of two studies on the pharmacokinetics of the combination product compared to already authorised formulations of the individual substances. The studies showed that there is no interaction between ivermectin and closantel in the combination product.

Pharmacodynamics

Endectocides can be used in animals to control internal and external parasites. One active substance Ivermectin is an endectocide; it acts by inhibiting nerve impulses. Ivermectin binds selectively and with high affinity to glutamate-gated chloride ion channels which occur in invertebrate nerve and muscle cells. This leads to an increase in the permeability of the cell membrane to chloride ions with hyperpolarisation of the nerve or muscle cell, resulting in paralysis and death of the parasite. Mammals do not have glutamate-gated ion channels so the Ivermectin will not affect them in the same way as it does the invertebrate parasites.

The other active substance closantel is a parasiticide with flukicide activity and efficacy against other helminths (e.g. roundworms) and arthropods. Closantel is a salicylanilide and acts by uncoupling oxidative phosphorylation.

Pharmacokinetics

Following administration by subcutaneous injection ivermectin is only partially metabolised. In cattle, about 1-2% is excreted as unaltered dung; the remainder is excreted as metabolites or degradation products. Salicylanilides are poorly metabolised and are excreted mainly unchanged. About 90% of closantel is excreted unchanged in the faeces and urine in cattle. Two pharmacokinetic studies were conduced with the proposed formulation. These studies were conducted in accordance with the Good Laboratory Practice (GLP). The first study was a comparative study of plasma levels of ivermectin and/or closantel in cattle following the subcutaneous administration of various formulations of Ivermectin/Closantel injection.The results indicated small differences in plasma levels of the relevant active substances between the formulations but there was no evidence that combining ivermectin and closantel in the formulation resulted in any significant interference with the bioavailability of either active substance. The second study was a two-part study incorporating a pharmacokinetic cross–over study in cattle comparing the test formulation and reference product with respect to ivermectin and a pharmacokinetic parallel study comparing the test formulation and reference product with respect to closantel.This study allowed comparisons between the test formulation and the pioneer single active substance products containing either ivermectin or closantel. With regard to closantal, both the test and reference products produced very similar blood profiles of closantel and the 90% Confidence Intervals for Cmax and AUC[4] were within the normal permitted range. Therefore, the test product was considered bioequivalent to the reference product. In the case of ivermectin, whilst the AUC values were similar for the test formulation and the reference product, the Cmax values indicated a more rapid uptake from the test article than from the pioneer product. The study also indicated that both products have a similar persistent effect and the claims for persistent activity are identical to those approved for pioneer ivermectin product.