Chapter Index

Anesthesia and tranquilizers

Anesthetic: suppresses sensory stimuli such as pain, feeling of heat or cold; local or systemic effect.
   Inhalant anesthetics (gases) or noninhalant anesthetics applied by injection.
Analgesics: primarily suppressing pain, central effect (for instance morphine)
Tranquilizer: calming down the animal, no anesthesia
Muscle relaxants = paralytic drugs: effect only on muscles, usually applied in combination of diminished doses of anesthetics to prevent seizures (Example: curare)
Ryder, 1978, tested drugs used for animals by trying the effects on himself; after an experimental dose of the tranquilizer Chlorpromazine for instance he was lying on his bed, believing that for an observer he might look tranquil and content, but he was just miserable. Ryder for instance regards muscle-relaxing drugs paralyzing without diminishing consciousness as inhumane, causing terror and trauma in the animal. He also notes considerable species differences in a variety of drugs, warning that a drug humane in one species may be inhumane in another one. 83
Anesthesia in lorises and pottos
Anesthesia in lorises is apparently difficult 32. In a field study on slow lorises, in 5 of 12 cases (seven attempts with Tiletamine/Zolazapam, four attempts with Ketaminhydrochloride) the effect of anesthesia was insufficient, the animals were only slightly benumbed or fully awake. Males apparently needed a higher dosage, independent from the anesthetic agent 80. Pottos, too, are "notoriously difficult to anesthetize for surgical treatment", probably due to their low basal metabolic rate 81.
Anestesia with Ketamine may cause an increase of body temperature for up to 10C 67. For anesthesia for taking of blood samples, use only of Ketaminhydrochloride is recommended because additional tranquilizers can influence the result 2.


Anesthetic agents and dosages used:

See also report by U. Streicher about experience with anesthesia in Nycticebus pygmaeus at the Endangered Primate Rescue Center, Vietnam.
Ketamine (from Ketaset, Fort Dodge Laboratories Inc., Fort Dodge, lowa, 50501 USA) 61,
used in slender lorises and lesser slow lorises (effect not documented) 61, in slow lorises: dosage 10-25 mg/kg 61.

Imalgène 500 (Ketaminhydrochloride from Rhône Mérieux, Lyon, France) 80,
used in slow lorises (N. c. coucang) in the field; none of the treated animals showed signs of health problems during or after anesthesia. Slower onset of effect than in Tiletamine/Zolazapam. Maximum dosage of 30 mg/kg recommended (Bonath, pers. comm., quoted in 80). A dosage of 12.5 mg/kg led to slightly slower movements in one male and one female and full anestesia for the reported interval 21 to 40 minutes in one female. A dosage of about 22 mg/kg in another female caused full anesthesia for the reported interval 0 - 20 minutes. A slightly higher dosage than recommended by Bonath in two males had an insufficient effect, only leading to slower reactions, a third male showed a satisfactory effect for the reported interval 0 - 20 minutes 80.

Tiletamine/Zolazapam(from Telazol, Fort Dodge Laboratories Inc., Fort Dodge, Iowa, 50501 USA) 61,
used in Loris (effect not documented); dosage in lesser slow lorises: 5 - 28 mg/kg ("a wide range of dosages have been used but 8-12 mg/kg, is the average dose used. Slow recoveries are associated with the higher dosages"). Dosage in slow lorises: 4-14 mg/kg 61. Provides better relaxation than ketamine 61.
Zoletil 50 (Tiletamine/Zolazapam from Fa. Virbac, Carros, France),
used in slow lorises (N. c. coucang) in the field; none of the treated animals showed signs of health problems during or after anesthesia. Onset of effect clearly earlier than in Ketaminhydrochloride
Maximum dosage of 30 mg/kg recommended (Bonath, pers. comm., quoted in 80), one attempt in a male with a lower dosage of 12,5 mg/kg led to no visible effect, three females treated with the same dosage showed a full effect for about 40 to more than 120 minutes 80.
Isoflurane(from Aerrane, Ohmeda PPD Inc., Liberty Comer, New Jersey, 07938 USA) 61,
used in slender lorises, lesser slow lorises and slow lorises (no information about dosage or effect) 61.

Recommendation for Loris :

Xylazine (Rompun®, Bayer, Leverkusen) in combination with ketaminhydrochloride (for instance Ketamin 10%, WDT, Garbsen) 63.

Advantage: good suppression of pain and good muscle relaxation by a low dose, dosage can be increased up to satisfactory effect, the effect of xylazin can be abolished with Yohimbin. (This, however, may lead to muscle seizures because the effect of ketamine is not diminished).
Disadvantage: the injected dose cannot be adapted to needed dosage as in gas anesthesia. Duration: about 1-2 hours (energy loss / cooling down must be considered).
So far little practical experience, one test in Loris with a dosage of 1 ml (50 mg) ketaminhydrochloride and 25 mg xylazine per kg bodyweight 63, one anesthesia in a N. pygmaeus successful 85.
Inhalation anesthesia with Methoxyfluorane (Methofane®, Janssen-Cilag), may be better than Halothane or Isoflurane because it is less toxic for the liver and less easily overdosed. Not yet tested in Loris, only in rats and mice.
Advantage: dosage well adaptable, quick recovery (as in any inhalation anesthesia). Anestesia without catching and handling is possible.
Disadvantage: detrimental to the liver.


Tranquilizers may reduce psychic stress and have a muscle-relaxing effect; during transport, muscle-relaxation and slower reactions caused by tranquilizers may cause problems because the animals cannot react properly on shaking of the transport box, protecting themselves from lesions84. Better effect by beta-blockers (animal calmer, but reflexes not impaired).

Diazepam (Valium) is an anxiolytic and muscle-relaxing drug. Slender lorises usually take it without problems when injected into a cricket or mixed with milk formula. At Ruhr-University consumption of one drop of Valiquid 0,3 By Hoffmann-La Roche (1 ml = 30 drops contain 10 mg Diazepam) led to careless-looking behaviour and, in some cases, play behaviour, with higher dosage equilibrium problems occured. An effect of Valium lasting from 3 to 12 hours in primates was recorded 82. Two very old, weak lorises who got Diazepam in milk formula before being euthanized drank a little and immediately fell asleep 15. Given before introduction of an excited male to a female, Valium in two cases led to normal, peaceful behaviour, in other cases, however, aggressive behaviour occurred even under a dosage causing equilibrium problems; therefore, animals should only be introduced to each other when showing no signs of excitement.

Privacy policy / Datenschutz

Back to the top of this page

Home Rescue Centers
Taxonomy, populations
Identification key Distribution maps Database for genera, species & populations
Info for field studies & wild population surveys Reintroduction to the wild Captive care
Conservation breeding
Diseases of lorises and pottos Behaviour General Info