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Nervous System Drugs

Terms in this set (50)

General Types of CNS Drugs (some drugs fit into more than one class)
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Tranquilizers
Provide sedation, decreased responsiveness, some pain control (analgesia) but not significant
Barbituates
Used to induce general anesthesia, decrease seizure activity and for euthanasia.
Dissociatives
Decrease body response, memory, and induce analgesia. Cause a feeling of being dissociated from the body and a lack of association with pain. Can produce a cataleptic state. Often retain body reflexes. Do not stop deep muscle pain when used alone, therefore not suitable for abdominal surgeries unless in combination with other drugs.
Opiods
Narcotic drugs used primarily for pain control and sedation. These are synthetic drugs and not true opiates. They produce narcosis which is a stuporous state of disorientation and analgesia.
Neuroleptanalgesics
For a form of anesthesia. Are combinations of an opioid and a tranquilizer or sedative.
Terms
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Analgesic
Is a drug that relieves pain without causing loss of consciousness.
Anesthetic
Is a drug that produces a lack of all sensation.
Catalepsy
A state of involuntary muscle rigidity that is accompanied by immobility, amnesia, and variable amounts of analgesia. Some reflexes may remain intact.
Amnesia
Loss of memory or recollection.
Neuroleptanalgesia
Joint administration of a tranquilizing drug and an analgesic especially for relief of surgical pain.
Tranquilizer
A drug that calms an animal without affecting consciousness.
Barbituate
A drug that depresses the CNS and produces anesthesia.
Drugs Affecting the Nervous System
Drugs affecting the Nervous System can be group according to function and purpose:
• Anesthetics
• Tranquilizers
• Sedatives
• Analgesics
• Anticonvulsants
• Stimulants
Anesthetics
Anesthesia means "without sensation". An anesthetized animal cannot feel stimulations of pain, cold, heat, pressure or touch.
General Anesthetics
Act on the brain (CNS) producing unconsciousness.
Local Anesthesia
Is the reversible loss of sensation in a regional area of the body without loss of consciousness.
Injectable Anesthetic Agents
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Barbituates
Four main uses:
• Short-term anesthesia

• Induction for general anesthesia

• Control seizures

• Euthanasia

Major side effects - respiratory and cardiac depression. May see cardiac arrhythmias and respiratory apnea.
Are non-reversible and must be metabolized by liver.
Extremely painful if injected perivascular. Some can produce momentary excitatory phase resulting in the animal paddling and vocalizing and acting in a frenzied state.

Barbiturates are classified according to their duration of action:

• Ultra-short acting (thiobarbiturates) 10-20 minutes thiopental sodium

• Short acting 1 hour Pentobarbital

• Long acting 4 - 7 hours Phenobarbital

Recovery of the longer acting barbiturates may produce "stormy" bouts and excitative episodes wherein the animal becomes agitated, excited or frenzied while semiconscious..
Greyhounds and other thin-bodied sight hounds metabolize thiobarbiturates very poorly. These dogs specialize in pursuing prey, keeping it in sight, and overpowering it by their great speed and agility. They are non-fat dogs and the lack of fat affects how the barbiturate acts in their system so are more at risk to these anesthetics.
Propofol
A short-acting injectable anesthetic agent similar to but unrelated to barbiturates. This drug is dissolved as a white emulsion made of egg lecithin, soybean oil and glycerol without preservatives; hence can be subject to bacterial growth and endotoxin production; must be discarded within 24 hours of opening. It is not irritating if given perivascular; produces rapid anesthesia and quick recovery (20 to 30 minutes) but poor analgesia when used alone.
Dissociative Anesthetics
The dissociative agents belong to a family of anesthetics that include ketamine and tiletamine. Involuntary muscle rigidity (catalepsy), amnesia, and analgesia characterize dissociative anesthesia. Ketamine is the major type of this drug.

Products: Ketaset, Vetalar, Ketalar.

Ketamine anesthesia is characterized by catalepsy and amnesia. Deep abdominal or visceral pain is not completely eliminated so poor analgesia is obtained. Tranquilizers are often administered concurrently with ketamine to increase muscle relaxation and deepen the level of anesthesia.
Ketamine is used especially in cats. Their eyes remain open and have no blink reflex. Hence an ophthalmic lubricant is used to coat the eyes to keep them moist.
Ketamine often produces a "delirious recovery". This is the "tennis match cat" seen in recovery because of its rhythmic back-and-forth head bobbing. Ketamine produces a burning sensation when administered IM and good restraint of the feline patient is essential. Ketamine can be administered via the mouth (absorbed through the mucous membranes) for very fractious and unmanageable cats.
Ketamine is a C-III controlled drug. It is chemically related to PCP ("angel dust") and is actively sought after by the drug crowd. It must be carefully controlled and logged in the clinic and be kept under lock and key.
Tiletamine - Telazol
Is a drug related to ketamine but comes combined with a tranquilizer. This produces a drug with good muscle relaxation and excellent deep body analgesia.
Inhalant Anesthetic Agents
Inhalant or gas anesthesia drugs are administered via the lungs and absorbed into the brain to produce general anesthesia. The drug comes as a liquid and is administered by vapourizing the drug liquid with oxygen (O2). Inhalants enter and leave the body via the respiratory system (lungs) and therefore do not require much biotransformation for elimination.
Halothane: Trade Name Fluothane.
Administered by means of a vapourizer. Is one of the older agents today. One normal side effect of halothane is that it lowers body temperature (hypothermia) and these surgical patients must be keep very warm. Is mostly metabolized by being excreted by the lungs. May cause tachypnea (↑ resp.)
Has mostly been superceded today by better agents.
Isoflurane: Trade Name Forane, IsoFlo
Gives rapid smooth induction and rapid recovery. This inhalant is not metabolized in the body and therefore is not toxic and allows for rapid, easy recoveries. Has a very pungent odour. May cause stormy recovery with cats.
Sevoflurane: Trade Name SevoFlo.
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Nitrous Oxide N2O (often called "laughing gas")
Is perhaps more properly referred to as an inhalant analgesic. The major purpose of nitrous oxide may be for decreasing the amount of the more potent inhalant anesthetics required to achieve a surgical plane of anesthesia. This gas is always placed in blue gas cylinders.
Local Anesthetic Agents
Animal is not unconscious, not even necessarily sedated (though this may be done) but sensation in an area is decreased or not present all together. "Freezing" like being at the dentist - same procedure and feeling - use this to explain to clients.
Local anesthetics work by preventing the conduction of nerve impulses in the peripheral nerves. Can be applied topically to mucous membranes or the cornea of the eye, by IV, by infiltration of a wound or in a joint, and directly around a nerve. Lasts only 5 to 30 minutes. Often will use if procedure is short enough to not require general anesthesia or we are worried about the risks of other methods. Local anesthetic agents recognized by name with "-caine" ending: lidocaine, proparacaine, tetracaine, etc.
Types, Methods and Uses
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Topical
On larynx (intubation of cats) with a spray, eye drops for taking pressure reading or exam, gel for injections or blood collection.
Infiltration of an Area
Multiple SQ injections around a wound or lump before procedure takes place.
Epidural
- Injection of an anesthetic agent into the spinal canal to provide loss of sensation in hind limbs.
Nerve Block
Injection into a specific area to numb a specific main nerve. Dentals, declaws, dewclaws, etc.
Tranquilizers/Sedatives
Tranquilizers and sedatives produce a relaxed state without much analgesia. This means an animal given one of these drugs and react quickly and aggressively to any sudden painful stimuli.
Tranquilizers
Are drugs that calm and are used to reduce anxiety and aggression.
Sedatives
Are drugs that decrease irritability and excitement.
ACE (acepromazine)
Is a phenothiazine tranquilizer without any analgesic effect. Commonly used to prevent motion sickness (car travel) in pets. Oral or injectable. Animals prone to seizures should not get ACE. Some cats may show frenzied behaviour when administered ACE. Can cause protrusion of third eyelid.
Droperidol
This tranquilizer is often combined with a narcotic analgesic called fentanyl, which then acts as a neuroleptanalgesic (Innovar-Vet). Used alone, droperidol is similar to acepromazine.
Diazepam and Others
Often used as a preanesthesia protocol to help with muscle relaxation and sedative effects.
Has stimulatory effect on appetite especially in cats but is no longer recommended due to liver failure..

Diazepam trade name = Valium.
Xylazine
Common trade name = Rompun. Used in dogs & cats. Can induce vomiting in some dogs and most cats. Good emetic for cats therefore. Used for sedative, analgesic and muscle relaxant effects. Often as a preanesthetic.

Used either IM or IV.

Can be reversed with antagonist drugs such as yohimbine (Yobine).
Medetomidine
Domitor

Similar to xylazine and more common in many clinics. Can cause muscle twitching in dogs.
Analgesics
Produce loss of perception of pain without loss of other senses.

Classed as narcotics and non-narcotics:
• Narcotics or opioids
• Neuroleptanalgesics
Narcotic/Opiates
Any drug produced from opium poppy.
Opioids
A drug produced synthetically.
General
All narcotic/opioid type drugs are C-II controlled substances. Produce analgesia and sedation.

Opioids are potent respiratory depressants. Also many animals become sound sensitive when given narcotics/opioids.
Often cause salivation, vomiting and defecation.

Tend to slow down GIT motility and hence used as anti-diarrheals.

Narcotics/opioids can be reversed (antagonized) by narcotic antagonists such as Naloxone or Trexan.
Examples of Narcotics/Opioids
• Morphine
• Meperidine (Demerol)
• Fentanyl
• Pentazocine (Talwin)
• Apomorphine
• Codeine
Neuroleptanalgesics
Drug combining an opioid and a tranquilizer.

Example includes Innovar-Vet a combination of fentanyl and droperidol. Mostly given IV.

Side effects can include: panting, flatulence, personality changes, sound sensitivity.

Antagonist is Naloxone.
CNS Stimulants
Used to stimulate respiration or reverse CNS depression.
Doxapram
Stimulates the respiratory centre in the brain (medulla). Common trade name- Dopram.

Mainly used to improve respiration in an anesthetized patient or for apnea in new born pups or kittens, especially if taken by C-section.
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