Polypharmacy

last authored: Jan 2010, David LaPierre
last reviewed:

 

Introduction

Polypharmacy is commonly used to describe multiple medications (>5), though it may also refer to unnecessary medications or medications used to treat side effects of others.

Perscriptions are vastly overused, driven by patients' need for 'a pill for every ill'.

Polypharmacy is dangerous, leading to side effects, hospitalizations, and death. Drug-drug interactions increase quickly with the number of drugs given, up to 100% for 8 drugs.

Some combinations are important, as occurs when treating HIV, H. pylori, or tuberculosis.

 

Mechanisms can occur in various ways:

 

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Pharmacological Considerations

Multiple drugs can compete, prevent, or antagonize each other.

Iron can chelate quinolones, levothyroxine, and L-dopa.

Seniors have less albumin, leading to inceased phsyiological activity of drugs such as warfarin.

Seniors also have slower phase I hepatic metabolism, leading to higher concentrations of meperidine, warfarin, and TCAs.

 

 

Evaluating Body Systems

Assume everyone over 80 has renal impairment.

Renal function should be estimated based on creatinine clearance.

 

 

 

Medication Dangers

  • dangerous medications
  • drug-drug interactions
  • drug-disease interactions
  • drug-food interactions

Inappropriate Drugs in the Elderly

drug

risk

alternative

NSAIDs

HTN, CHF, PUD, renal failure

acetaminophen

meperidine

delirium

acetaminophen, morphine, hydromorphone

metaclopramide

extrapyramidal side effects

domperidone

amytriptiline, doxepin

anticholinergic, confusion, postural hypotension

SSRIs, nortryptiline, desipramine

fluoxetine

long half-life

citalopram, sertraline

diazepam, etc

confusion, falls, fractures, MVA, addiction

 

avoid BZPs; choose trazodone, lorazepam, oxazepam, temazepam if necessary

benztropine

anticholinergic

decrease or stop neuroleptic

diphenhydramine, hydroxyzine

anticholinergic

loratadine, fexofenadine
     

 

Septra

Medication Interactions

Some common interactions are listed here; it is much wiser to consult databases such as:

  • Lexicomp
  • ff
  • ff

 

Warfarin can be affected by antiobiotics, as gut flora synthesize vitamin K. Antibiotics can alccordingly lead to elevated function of warfarin.

Warfarin also has interactions with NSAIDs.

Disease-Drug Interactions

HTN - NSAIDS

peptic ulcers - NSAIDS

urinary outlet dysfunction - anticholinergics, antihistamines, oxybutinin

Parkinson's disease - metoclopromide, neuroleptics

constipation - Ca blockers, anticholinergics, TCAs

NASIDs - HTN

NSAIDS - CHF

Food-Drug Interactions

The most common is pharmacokinetic, where food increases or decreases absorption or availability.

 

 

 

 

Prescribing cascade: one new drug leads to side effects, for which a new drug is perscribed, for which a new drug is prescribed

 

activties of daily living: can do when on call

independent activites of daily living: cannot do when on call

 

 

Drugs commonly dosed too high

drug

upper limit of normal

adverse effects

HCTZ

25mg

no more effective if higher; can lead to dec Na or K, inc glucose

digoxin

0.125 mg

toxicity: delirium, nausea, arrhythmia

iron

325 mg

abdominal pain, constipation; no additional benefit

neuroleptics

haloperidol >3mg

postural hypotension, parkinsonism, falls, akathesia
     

 

 

Drugs Commonly Dosed Too Low

drug

upper limit of normal

ACE inhibitors

increase to enalapril 10 BID, lisinopril 40 OD, or ramipril 10 OD if K, CR, and BP allow

SSRIs, venlafaxine

start low, increase dose to maximum until therapeutic effect or side effects

warfarin

start low, increase to therapeutuc INR (2-3 for atrial fibrillation)
   

 

 

 

 

Clinical Usage and Tips

start low, go slow

stpo slow

treat to target

every new symptoms is due to a drug, unless provedn otherwise

avoid multiple prescribers

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Risk Factors

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Adverse Events

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Additional Resources

 

 

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