One drug or two—the risks and benefits of combining psychotropic medications (Proceedings)


One drug or two—the risks and benefits of combining psychotropic medications (Proceedings)

Aug 01, 2010

Factors to consider before prescribing a psychoactive drug
Does this patient need a drug?
      What is the diagnosis?
      What is the intensity of the behavior?
      Has prior therapy been appropriately implemented?
           Examine past behavioral and environmental modification steps

Selecting the primary medication
      Mechanism of action
           Class of medication

      Type of medication
Licensed drug
      Extra-label vs FDA approved

      Familiarity of prescriber with the product
      Client factors
            Tolerance for side effects

      Pet factors
            Concurrent medical conditions & medications
            Risk of side effects

Evaluating the response to single drug therapy
      Side effects
      Effect on target behavior
            Percent improvement
                 If inadequate, has there been enough time for full response?
                  Reevaluate dosage

Indications for combination therapy
      Slow onset chronic drug may be temporarily paired with rapid onset drug
      Partial response to primary drug at adequate dose
      Dosage of primary drug cannot be increased without intolerable side effects

Will the combination be safe?
      Consider inhibition or potentiation of cytochrome p450 enzyme systems
      Side effects may be additive
      Dosage adjustments may be needed
            Prepare to adjust dosages of non-psychotropic medications
      Some drugs combinations are contraindicated
            Eg no MAO with SSRI

Selecting adjunct medication
      Diagnosis and intensity of behavior problem(s)
      Age, overall health and species of patient
      Side profile of primary drug
      Time to therapeutic effect
      Class of drug
            Need extra care if two drugs are in the same family
            Serotonin syndrome

Patient monitoring for patients on multiple drug regimen

Pretreatment baseline laboratory testing
      CBC / serum chemistry profile / thyroid baseline

Reassess CBC / serum chemistry profile in one month and three months

Additional retesting every 3 – 6 months

Client consent
The use of many psychotropic medications in animals may still be viewed as experimental. Extra-label use of drugs is common practice. There is little published information available regarding combination therapy. A decision to use multiple medications should be made with full client consent, and with the understanding that the potential benefit to the patient outweighs any risk.

Behavior modification
It is rare for psychoactive drugs to be sufficient to eliminate or adequately control most behavior problems. Environmental and behavioral modification may be at least as important as the pharmacological intervention. During follow-up evaluations, confirm that clients are implementing the prescribed interventions appropriately. Offer additional treatment strategies as the patient continues to improve.