Prescription and drug interactions in the elderly
- Introduction :
- Polypathology is a legitimate indication for polymedication.
- Medications can help alleviate symptoms, prevent certain complications and sometimes even cure them.
At the same time, polymedication:
- increases the iatrogenic risk,
- decreases the quality of compliance and has a high cost.
- The introduction of any new treatment must therefore be carefully considered.
- Treatment goals and modalities should take into account comorbidities and quality of compliance.
II . Non-optimal drug prescription modalities:
- There are several modalities of non-optimal prescription:
- • Overuse , concerns the prescription of drugs for which there is no indication or which have limited effectiveness.
- • Inappropriate prescription (“misuse”) : the risk of the drug exceeds the expected benefit
- Underuse : under-consumption of treatment .
III. Iatrogeny :
An iatrogenic accident = Any harmful and unintended reaction to a drug occurring at doses used in humans, for prophylaxis, diagnosis or treatment purposes.
- It excludes voluntary or accidental poisoning and drug addiction, but also errors of observance” (World Health Organization, 1969).
- In elderly subjects, iatrogenic accidents are more frequent, more serious, and more costly than those in younger subjects.
- The iatrogenic risk is not inevitable: polymedication is the main iatrogenic risk factor in the elderly.
3 major groups of drugs are incriminated:
- Cardiovascular drugs
- Psychotropic drugs
- Nonsteroidal anti-inflammatory drugs, corticosteroids and antiparkinsonian drugs. Accidents are most often observed with the taking of commonly used medications.
Causes of iatrogenesis:
- Drug-related causes
- . Lack of therapeutic education of patients:
a. Monitoring not or poorly prescribed
b. Not or poorly understood
c. Not or poorly transmitted.
Prescription and drug interactions in the elderly
Situations at risk of iatrogenesis:
Vigilance should be increased when prescribing:
• A drug with a narrow therapeutic margin,
• A psychotropic drug,
• A cardiovascular drug,
• A drug recently put on the market,
• A combination of active products,
• Several drugs with the same pharmacological property, • Pathologies increasing the iatrogenic risk.
This vigilance is all the more important as the subjects are/have:
• Polypathological,
• Renal insufficiency,
• Malnourished,
• Locomotor disorders,
• A sensory deficit,
• Locomotor disorders (beware of medications that promote the occurrence of orthostatic hypotension or dizziness or which have a myorelaxant effect.
Assess compliance:
It is defined as the degree of concordance between an individual’s behavior (medication intake, diet, and/or lifestyle changes) and medical prescriptions or recommendations. It is important to assess it during follow-up. The most common compliance errors are:
• Forgotten plugs
• Dosing errors (over- or under-dosing)
• failure to comply with the conditions of taking
- Self-medication.
Practical rules of prescription:
Some rules to improve prescribing in the elderly:
• Do not prescribe without diagnostic analysis,
• Optimize the benefit/risk ratio: establish priorities,
• Assess the patient’s fitness,
• Choose a suitable drug class and dosage form,
• Think about the dosage.
Educate the patient
• Specify the action to take in the event of forgetting or not taking each medication
• List the situations which should lead you to consult your doctor.
• Explain the need to inform each doctor consulted of the treatment in progress, including medications taken as self-medication.
Need for appropriate and vigilant monitoring:
When treatment is initiated, specific therapeutic objectives must be set:
• on which clinical or non-clinical elements the effectiveness of the treatment, its tolerance and at what frequency will be measured.
• If partial or ineffective, a specific strategy must be developed.
• Medical monitoring is all the closer if the subject has multiple pathologies,
that he has disabilities that hinder his compliance
, that he is taking medications with a narrow therapeutic margin or that may interact.
Prescription and drug interactions in the elderly
Changes in drug pharmacokinetics and pharmacodynamics
In general, liver and kidney function deteriorate with age, and this is even more the older the age. For example, glomerular filtration decreases by 25% at age 75 and by 50% at age 90, which significantly reduces the elimination of drugs filtered through the glomerular capillaries.
The alteration of renal function associated with the reduction of hepatic degradation capacities requires, for certain drugs, a reduction in their usual dosage.
Absorption modification
reduction of gastric acid secretion,
decreased rate of gastric emptying,
reduction in the digestive resorption surface
decreased digestive perfusion.
Changes in distribution and transport
With age there is a decrease in total water and lean body mass, which increases the risk of overdose for water-soluble drugs.
In addition, the increase in lipid mass increases the risk of prolonged storage and release of fat-soluble drugs, which often leads to an increase in the half-life. (Example: lengthening of the half-life of benzodiazepines which can go from forty hours in young subjects to four to five days in elderly subjects)
The modification of plasma transport is reflected by hypoalbuminemia which reduces the fixation of drugs strongly bound to albumin, thus increasing their free fraction and therefore potentially their toxicity (example: digoxin, hypoglycemic sulfonamides, anti-vitamin K, non-steroidal anti-inflammatories, etc.).
Prescription and drug interactions in the elderly
Modification of hepatic metabolism
Hepatic drug transformation rate often decreased by reduced liver mass and hepatic blood flow
Naproxen® and Ibuprofen have reduced hepatic metabolism
Change in renal elimination:
Classically, presence of chronic renal failure among other things because the glomerular blood flow is lowered. The decrease in glomerular filtration is 2 to 10% per decade. Therefore decrease in urinary excretion of certain drugs: (aminoside, digoxin, angiotensin converting enzyme inhibitors, low molecular weight heparin) .
Prescription and drug interactions in the elderly
Other risk factors
Multiple chronic diseases: polymedication
Multiple doctors: which can lead to polymedication. Treatments are often changed by one doctor without consulting other practitioners. This increases the risk of iatrogenic interaction. In dentistry, you should try to prescribe as little as possible.
General principles of therapeutic prescription in the elderly in odontostomatology:
The therapeutic act is not limited to the prescription of medications . It also includes a non-drug and psychological approach:
Before prescription:
● listen, examine: prescribing a medication is not always the most appropriate response to the patient’s complaint.
● know the patient’s current pathologies and their history (hypertension, diabetes, heart disease, renal failure, etc.); know all the medications taken by the patient
● assess weight, blood pressure, hydration status and nutritional status.
● ensure a diagnosis
● choose the medicine:
– having the fewest side effects and interactions,
– having the widest safety margin,
– having the shortest half-life,
– having the route of administration and the pharmaceutical form most suited to the patient’s disabilities (tremors, visual disturbances, cognitive disturbances, difficulties with manual gripping, etc.).
● avoid duplication by identifying all medicines that belong to the same therapeutic class, which contain the same active ingredient.
Conclusion
Polymedication and drug interactions in the elderly remain a real public health issue, especially as life expectancy continues to increase. Better coordination between different health professionals seems essential and deserves to be developed. It should not be forgotten that in the elderly, medication should not be the only treatment and it is necessary to promote all non-drug therapeutic approaches.
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