Introduction
Prescribing for elderly patients presents several challenges, most of which have not changed in the past 20-30 years. Challenges in pharmacodynamics and pharmacokinectics means that these patients often need lower doses, and the presence of multiple medical problems and subsequent polypharmacy makes adverse drug reactions and interactions inevitable. Therefore, these patients may benefit from regular specialist review by a geriatrician.
2.1 Physiological Changes that Occur with aging?
a. Pharmacokinetic / pharmacodynamic changes:
With age, the body undergoes several changes that affect the distribution, metabolism and excretion of drugs. These changes include:
- Reduction in renal clearance (very important)
- Liver size; lean body mass;
- Hepatic enzyme activity and serum albumin may be reduced in the presence of chronic disease.
Reduction in renal clearance results in reduced excretion of water – soluble drugs and this is especially important for drugs with a narrow therapeutic index (window), such as digoxin , lithium and gentamycin .
Older people are also more sensitive to the effects of some drugs, especially those that act on the central nervous system (CNS) such as: benzodiazepines, which are associated with an increase in postural sway and risk of falls.
b) Multiple pathology and polypharmacy.
Polypharmacy is common in older people – around 20% of people over 70 years take five or more drugs. Polypharmacy may not imply inappropriate prescribing, because all of the prescribed drugs may have an appropriate indication.
Polypharmacy is associated with increases in many adverse outcomes, including drug interactions, adrs, falls, hospital admissions/ readmissions, increased length of hospital stay, and mortality rate. However, these effects may result from multiple pathology or frailty, as opposed to being independent risk factors.
c) Inappropriate Prescribing (IP):
IP for older patients encompasses all of the normal indicators of inappropriate prescribing for adults in general, but the problem is especially relevant to older patients because they often take a large number of drugs. Not only does this increase their chance of having an adverse event, but it means that unnecessary drugs may be obscured by the large number of necessary ones.
Dose, formulation, and delivery need to be adjusted according to the age and frailty of the patient and some drugs are best avoided altogether.
Beers Criteria (1st published in 1991; last updated 2003) – It is an American consensus guideline for problematic drugs for older patients.
For example, angioterisin converting enzyme inhibitors (ACEIs) induce cough, regardless of the age, though may be more severe in the old. Warfarin reduces strokes in patients with atrial fibrillation, with no significant increase in the risk of bleeding, and it’s recommended for most patients over 75 years with atrial fibrillation.
Good Prescribing Practice Guidelines:
- Carry out regular medication review. Discuss and agree all the changes with the patient.
- Stop any current drugs that are not indicated.
- Prescribe new drugs that have clear indication
- If possible, avoid drugs that have known deleterious efforts in elderly patients, such as benzodiazepines, and recommend dosage reduction when appropriate.
- Use the recommended dosages for elderly patients
- Use simple drug regimens and appropriate administration systems.
- Consider using once daily or once weekly formulations and use fixed dose combinations when possible
- Consider non- pharmacological treatments ( if appropriate)
- Where possible, avoid treating adverse drug reactions with further drugs
Note: Without the clinical records, pharmacist can’t review the indications for treatment, where they are expected to spot adrs, drug interactions and concordance problems.
Future Improvements
Randomized controlled trials of new treatments should, ideally, include representative samples of elderly population with comorbidities.
Conclusions
Medications for the elderly persons present many problems, due to the changes in their pharmacokinetic and pharmacodynamic profiles.
Often, they need lower doses because of presence of multiple medical problems, polypharmacy, adrs and drug interactions.