Fundamentals of Pharmacology
for Veterinary Technicians
Chapter 22
Behavior-Modifying Drugs
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Basic Terminology
• The use of drugs to treat problem
behaviors is only a small part of treating
animal behavior problems
– Must correctly diagnose the condition,
examine the social conditions, and alter
external stimuli
• Potential side effects of long-term use
– Liver, kidney, and cardiovascular problems
• Used extra-label
– Must have veterinarian/client/patient
relationship
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Classes of Behavior-Modifying
Drugs
– Anti-anxiety drugs
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Antihistamines
Benzodiazepines
Phenothiazines
Azapirones
Barbiturates
– Antidepressants
• Tricyclics
• Monoamine oxidase inhibitors
• Selective serotonin reuptake inhibitors
– Hormones
• Progestins
• Estrogen
• Testosterone inhibitors
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Anti-anxiety Drugs
• Anti-anxiety drugs attempt to decrease
anxiety
• Types of anti-anxiety drugs
– Antihistamines produce some degree of
sedation because they suppress the CNS
• Used to treat anxiety associated with pruritus; the
antipruritic effects of antihistamines appear to lessen
this anxiety as well
• Examples include hydroxyzine and
diphenhydramine
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Anti-anxiety Drugs
• Types of anti-anxiety drugs (cont.)
– Benzodiazepines
• Are chemically related compounds used to relieve
anxiety; appear to work on the limbic system of the
brain by potentiating GABA
• Bind to specific sites in the brain; appear to produce
sedation and relieve anxiety
• Used to treat aggression, urine spraying, and noise
phobias
• Examples include diazepam, chlordiazepoxide,
lorazepam, flumazenil, and alprazolam
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Anti-anxiety Drugs
• Types of anti-anxiety drugs (cont.)
– Phenothiazines
• Are chemically related compounds that
work by antagonism of dopamine
(increased dopamine levels are associated
with some psychotic diseases)
• Used to treat aggression (however, may
make animals more reactive to noise)
• Examples include chlorpromazine,
acepromazine, promazine, perphenazine,
and prochlorperazine
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Anti-anxiety Drugs
• Types of anti-anxiety drugs (cont.)
– Azapirones
• Chemically different from other anti-anxiety drugs;
do not cause sedation
• Work by blocking serotonin; used to treat urine
spraying and anxiety-associated aggression
• An example is buspirone
– Barbiturates
• Have anti-anxiety action due to their ability to cause
CNS depression (they have an effect on GABA)
• Used to control vocalization in cats and seizure-like
anxiety in dogs
• Examples include phenobarbital and carbamazepine
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Antidepressant Drugs
• Antidepressant drugs are used to treat various
mood changes (including aggression) and
cognitive dysfunction in animals
• Transmission of nerve impulses between two
nerves or between a nerve and tissue takes
place via the release of neurotransmitters from
storage sites at the nerve terminal
• After the neurotransmitter combines with the
appropriate receptors, reduction of
neurotransmitter concentration occurs
– One mechanism involves the reuptake of
neurotransmitter
– Another mechanism involves destruction of
neurotransmitter by monoamine oxidase (MAO)
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Antidepressant Drugs
• Tricyclic antidepressants (TCAs)
– Work by interfering with the reuptake of serotonin by the
presynaptic nerve cell; its metabolites inhibit the
reuptake of norepinephrine
– Increases the concentration of neurotransmitter at
postsynaptic receptors in the CNS
– Used to treat separation anxiety, pruritic conditions, and
compulsive disorders in animals
– Side effects include anticholinergic effects, liver
problems, and thyroid effects
– Examples include amitriptyline, imipramine,
clomipramine, and doxepin
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Antidepressant Drugs
• Monoamine oxidase inhibitors (MAOIs)
– Work by inhibiting the enzyme monoamine
oxidase, thus reducing the destruction of
dopamine, norepinephrine, and epinephrine
– MAOIs irreversibly inhibit MAO
– Used to treat cognitive dysfunction in dogs
– Side effects include hypotension, drowsiness,
and anticholinergic effects
– An example approved for dogs is selegiline;
extra-label examples include phenelzine,
isocarboxazid, and tranylcypromine sulfate
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Antidepressant Drugs
• Selective serotonin reuptake inhibitors
(SSRIs)
– Work by inhibiting serotonin reuptake,
resulting in increased serotonin
neurotransmission
– Used to treat depression, aggression, anxiety,
phobias, and compulsive disorders
– Side effects are few
– Examples include fluoxetine, sertraline, and
paroxetine
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Hormones
• Progestins and estrogens have calming effects
due to their suppression of the excitatory effects
of glutamine and their suppression of male-like
behaviors
• Side effects include mammary gland hyperplasia,
endometrial hyperplasia, bone marrow
suppression, and endocrine disorders
• Examples include
– Diethylstilbestrol: used for urinary incontinence
– Medroxyprogestone acetate: used to treat male-like
behaviors
– Megestrol acetate: used to treat urine spraying, anxiety,
aggression, and dermatitis conditions
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Hormones
• Testosterone inhibitors inhibit the
production of testosterone or block
enzymes that convert testosterone to
dihydrotestosterone (its potent form)
• Used to treat aggression in male dogs
• An example is delmadinone, which is
used to treat aggression in male dogs
• The human product finasteride is used to
treat benign prostatic hyperplasia and
may be used in the future in veterinary
medicine
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.