Fundamentals of Pharmacology for Veterinary Technicians

1. Fundamentals of Pharmacology for Veterinary Technicians Chapter 22 Behavior-Modifying Drugs © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

2. 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.

3. Classes of Behavior-Modifying Drugs • Anti-anxiety drugs • 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.