Drugs for Restraint of Wild Animals

The drugs for restraint of wild animals characteristics that are expected with use of any type of chemical agent needs to be well understood before one resorts into chemical immobilisation in any wild animal species.

Ideal features if an immobilizing drug are given below:

• Low cost
• No side effects
• Rapid absorption and rapid action.
• Need of concentrated form (small quantity for injection via dart syringe is convenient for field usage).
• Permitted for use in animals for human consumption.
• Effective immobilization-effects.
• Reversible by the injection of an antidote.
• Safe for the handler as well as to the targeted wild animal species.
• Wide safety margin.
• Should not irritate the muscle.
• Capable of remaining stable in solution for long periods of time at room temperature.
• Short induction period.

This helps many times to avoid the untoward incidences that are likely to arise due to the chemical immobilization in case of wild fauna.

Drugs for Restraint of Wild Animals

Xylazine

Xylazine is one of the alpha two adrenoceptor agonist and is available both in powder and solution forms.

Effects of xylazine based immobilisation

• Animals appear sleeping
• Snoring sounds will be heard at a distance in species like elephants
• Dullness
• Reduced movements

Analgesia lasts for fifteen to thirty minutes and after this period, painful techniques should not be undertaken, in general. However, it is to be noted that a sleep like state is maintained for almost about an hour to two hours.

Caution

It is significant to note that the seemingly sedated animal may get up explosively causing concern to the safety of the persons nearby.

If the dose rate is exceeded, death may occur and hence, correct judgment of the dose rate depending on the species needs to be made if one wants to have a success in it’s usage in various species of wild animals. Atropine may be of useful to reduce the drug effects of xylazine.

Antidote for xylazine

Yohimbine at the dose rate of 0.125 mg per Kg body weight and Doxapram hydrochloride may be used as a respiratory stimulant.

Ketamine

Ketamine is the derivative of phencyclidine derivative and is a dissociative anaesthetic. Animal administered with ketamine generally retains the reflexes which is considered as advantageous one with regard to the minimizing of hazards of inhalation of food or ingesta. Eyelids remain open and eyes have a fixed expression. However, it may not produce skeletal muscle relaxation.

Ketamine crosses the placenta in case of pregnant wild animals and however, it is known to cause no abortion in case of wild animals.

Use of Ketamine in wild animals

Wide dose rate is noticed (2 to 50 mg per kg body weight). Effects of parenteral injection occur within three to five minutes. Convulsions may occur in case of felids. This drug is not much suitable one in case of herbivores in general. However this is much useful in case of carnivores, reptiles and avifauna.

Cautions during the usage of ketamine:

• This drug should not be mixed with barbiturates in the same range.
• Hyperthermia is a side effect of this drug.

Tiletamine

Tiletamine is one of the cyclohexanone dissociative agent related to ketamine.

This is often combined with zolazepam hydrochloride which is a nonphenothiazine pyrazolodiazepinone tranquilizer.

This combination helps to reduce the occurrence of seizures which are likely to occur more if tiletamine alone is used in the wild animals.

Etorphine

Etorphine  is a narcotic drug to be used with more clinical cautions. This is the synthetic derivative of opium alkaloid and has about ten thousand times the analgesic properties of morphine sulphate.

This drug has 10,000 times the analgesic properties of morphine. Anaesthesia occurs in ten to twenty minutes.

Recovery is slow without antidote and in such occasions, the recovery may take as much as seven hours. However, when antidote is used, the wild animal may become mobile or ambulatory within a period of about four to ten minutes.

Legal formalities are to be taken care of while using etorphine like drugs.

The animal may have tachycardia and may either get stimulated or depressed depending on the dose-response and the species of the wild animal.

Use of etorphine in wild animal

This drug is used in large sized herbivores like elephant, hippopotamus, giraffe, sambar deer etc. Large animal formulation of Immobilon contains 2.45 mg/ml Etorphine mixed with 10mg/ml Acepromazine maleate which is a phenothiazine derivative.

Antidote of Etorphine

Diprenorphine is the antidote to be used for etorphine. The standard dose is double the amount of etorphine injected.

Cautions to be undertaken while using etorphine:

• Should not be used with atropine, since the atropine may reduce the solubility of the drug.
• Animal may develop hyperthermia.
• Passive regurgitation may occur in cases of prolonged immobilization with etorphine.
• Injured wild animals may require slightly high dose rate of etorphine.
• Human-health hazard related factors need to be taken care of like avoidance of accidental falling on skin or eyes of the handling wildlife veterinarian and person who knows how to give I/V in human being may accompany the operation and such action may be of useful in cases of accidental emergencies. Equipment for artificial respiration should be available in the spot. Always wear gloves and glasses during usage of etorphine. When morphine drugs are handled, a stock of Narcan (human antidote) and diprenorphine (animal antidote) must always be available.

Acepromazine

Acepromazine is generally not used alone and often, a combination is used with ketamine or etorphine.

The muscle relaxant effects are unique ones when used in combination with ketamine.

Fentanyl and Carfentanyl

Fentanyl is a morphine derivative and is about one hundred and eighty times more potent than the morphine as an analgesic. This drug is often combined with droperidol which is a tranquilizer.

Though the effects start in about ten minutes, the effects may persist for about forty minutes.

Use in wild animals

The combination of droperidol with Fentanyl may be used in various species of wild animals especially carnivores, nonhuman primates and various small mammals among the wild animal species.

Antidote

Naloxone hydrochloride is an antidote to be used at the dose rate of 0.006 mg per Kg body weight.

Carfentanyl may be used in wild animals but is one of the costly drugs and is a narcotic one.

Anaesthetics Used in Zoo

Characteristics of Anaesthetics

• Should be cheap
• Should be easily available
• Needs to be fast in induction of Anaesthesia.
• There should be minimal side effects
• Complications should not be there in general
• Should have more merits technically

Anaesthetics Commonly Used

Gaseous Anesthetics

Halothane

• It is a halogenated hydrocarbon.
• It’s usage is on decrease due to increased popularity of isoflurane and sevoflurane.
• Side effects: Development of arrhythmia.
• Demerits: Limited availability.

Nitrous Oxide

• Nitrous Oxide is not used as a solo anaesthetic due to its low potency. It is commonly used as 50% mixture with balance of the mix being oxygen.
• Contraindications: This is contraindicated in animals with pneumothorax, gastric dilatation, gas embolism, etc.

Isoflurane

• This is the most widely used veterinary inhalant anaesthetic.
• This is stable and potent.
• This has a high saturated vapour pressure.
• Merits: Metabolism of isoflurane is minimal and fluoride induced nephrotoxicity is uncommon.

Desflurane

Limited use in veterinary medicine.

Injectable Anaesthetics

Barbiturates

• This causes anasethesia through depression of CNS activity. Eg. Thiopental, pentobarbital etc.
• Demerits: Perivascular injection can lead to tissue necrosis.
• Their use in non domestic species due to practical “inability” to obtain reliable intravenous access prior to anaesthetic induction.