Rational use of medicines in the elderly

With the increasing use of drugs by the elderly, not only does the adverse drug reactions increase, resulting in an increase in drug-induced diseases, but it also affects the condition of the primary disease, causing difficulties in diagnosis and treatment.

Rational use of medicines means safe, effective, economical and necessary individualized medication.

The requirements proposed by WHO for rational use of medicines are: prescribing medicines according to symptoms, providing medicines in a timely manner, low prices, accurate dispensing of medicines, correct dosages, intervals and times of use, and medicines must be effective, of qualified quality, and safe and harmless.

The WHO standard for rational drug use is:

① The prescribed medicine should be an appropriate medicine;

② Ensure the supply of medicines at an appropriate time and at a price that the public can afford;

③ Correctly adjust the prescription;

④ Take the medicine in the standard dosage, correct usage and number of days;

⑤ Ensure the quality, safety and effectiveness of drugs.

Rational use of medicines is relative. Today, it is generally recognized that rational use of medicines should include the four basic elements of safety, effectiveness, economy and necessity.

As people age, the physiological functions and anatomical structures of important organs in the elderly body decline to varying degrees. Therefore, the pharmacokinetics, pharmacodynamics, adverse reactions and toxic side effects of drugs in the elderly body may undergo a series of changes different from those of young people, making the therapeutic dose and toxic dose of drugs for the elderly closer. In addition, most elderly people are prone to multiple diseases and need to use multiple drugs for treatment at the same time, which may easily cause drug interactions and increase the incidence of drug toxicity. Furthermore, the individual differences between the elderly are greater than those between young people. Therefore, the types and dosages of drugs used by the elderly need to vary from person to person. In short, the particularity of drug use caused by physiological changes in the elderly makes it particularly important for the elderly to use drugs rationally and administer drugs individually.

Changes in physiological characteristics of the elderly and rational use of drugs

(I) As the nervous system ages, the number of brain cells decreases, the weight of brain cells decreases, cerebral vascular resistance increases, cerebral blood flow decreases, brain enzyme activity decreases, brain metabolism decreases, and brain oxygen consumption decreases. Changes in the central nervous system of the elderly cause the elderly to be more sensitive to central nervous system depressants. For example, the elderly are more sensitive to benzodiazepines (such as diazepam), morphine, barbiturates, ethanol, and chlordiazepoxide than young people, especially to anticholinergics and antihistamines used to treat Parkinson's disease. Therefore, when the elderly use central nervous system depressants, due to their increased sensitivity to such drugs, their efficacy is enhanced and the incidence of adverse reactions increases. The general dosage is 1/2 of that of young people.

Changes in the elderly's nervous system affect medication, including:

(1) Poor memory can easily lead to medication errors. For drugs that require a stable blood concentration, pathological symptoms often occur due to missed doses, or toxic side effects occur due to overdosing.

(2) Drugs that are toxic to the nervous system should be used with caution because their toxicity is often increased.

(II) Cardiovascular system: The heart gradually enlarges, the hardness of blood vessels increases, the elasticity decreases, the cardiac output decreases, the number and density of beta receptors decrease, the affinity decreases, resulting in their functional decline, the activity of the renin-angiotensin-aldosterone system decreases, and the activity of cyclic adenosine succinate enzyme also changes. Therefore, the cardiovascular function of the elderly is reduced, the blood pressure regulation function is reduced, and the coagulation function is weakened. This series of changes affects the effect of the drug and the occurrence of toxic and side effects. The changes in the cardiovascular system of the elderly have the following effects on medication:

(1) Elderly people are less sensitive to the positive inotropic effects of digitalis glycosides, but more sensitive to their toxic reactions, which makes the safe range of digitalis treatment narrower and more prone to poisoning. Therefore, when using digitalis drugs for the elderly, special attention should be paid to the dosage and individualized administration. Generally, it can be 1/4 of that for young and middle-aged people.

(2) When elderly patients with hypertension are treated with antihypertensive drugs, although they can lower blood pressure, reduce complications and mortality, they are prone to postural hypotension. This is especially likely to occur when taking beta-blockers and adrenergic nerve blockers; taking very sensitive central nervous system antihypertensive drugs such as clonidine and methyldopa can cause severe adverse reactions such as drowsiness and dizziness. In particular, sudden discontinuation of the drug can cause anxiety, agitation, palpitations, sweating, increased blood pressure, and even withdrawal reactions such as hypertensive crisis. When taking reserpine to lower blood pressure, it is easy to cause depression and peptic ulcers. In short, the treatment of hypertension in the elderly should be based on diuretics, supplemented by other antihypertensive drugs. Diuretics should be started at a small dose, generally 1/2 of that of young people, and taken in the morning. (3) The vasodilator effect of nitroglycerin is significantly enhanced in the elderly, and the dose should be appropriately reduced. The heart rate-increasing effect of isoproterenol and the heart rate-decelerating effect of propranolol are weaker in the elderly than in young people, and the dose should be appropriately increased.

(4) Use antihypertensive drugs and diuretics with caution to avoid orthostatic hypotension.

(5) Attention should be paid to the control of hyperthyroidism and infection, especially lung infection, and the dosage of infusion should be noted.

The kidneys are the main organ for excretion of most drugs and their metabolites. With age, the renal blood flow of the elderly is only 50% of that of adults, the number of functional glomeruli decreases, and the glomerular and tubular functions decline, thus reducing the glomerular filtration, tubular secretion and reabsorption functions. Therefore, even if the elderly do not have kidney disease, the excretion of drugs that are mainly excreted through the kidneys in their original form or metabolites with high nephrotoxicity will gradually decrease, resulting in a decrease in the renal clearance rate of the drug, a prolonged t1/2, and accumulation of the drug in the body, increasing toxic and side effects. The changes in the kidneys of the elderly affect the use of drugs in the following ways:

(1) The dosage of drugs that need to be eliminated by the kidneys should be adjusted. For example, allopurinol, procainamide, methyldopa, digoxin, furosemide, ethambutol, cimetidine, phenobarbital, lithium salts, aminoglycoside antibiotics, penicillin G, and high-dose cephalosporins, nitrofurantoin, and amantadine. When these drugs are used in the elderly, attention should be paid to adjusting the dosage and dosing interval. If conditions permit, it is best to formulate a reasonable individualized dosing plan based on the measured blood drug concentration level to truly improve the efficacy of the drug and reduce toxic and side effects.

(2) Close attention should be paid to the balance of body fluids and electrolytes to prevent disturbances.

Digestive system

1. Increased gastric pH;

2. Stomach emptying slows down;

3. Decreased gastrointestinal blood flow velocity;

4. The intestinal absorption surface and cells with absorption function are reduced.

Some drugs and nutrients absorbed through active transport mechanisms, such as galactose, glucose, vitamin B, iron, and calcium, are absorbed less in the elderly. Because the elderly suffer from multiple diseases at the same time, they often need to take multiple drugs at the same time, so that the drugs can affect each other's absorption. For example, antacids and laxatives can reduce the dissolution and absorption of other drugs.

The main liver changes in the elderly are:

(1) Liver weight decreased by approximately 20%.

(2) Liver blood flow decreases by approximately 40% to 45%.

(3) Functional leukopenia.

(4) The production of albumin and coagulation factors is reduced.

(5) The activity of drug enzymes in the liver is reduced.

These physiological changes have a greater impact on drugs that are mainly inactivated by liver metabolism or activated by the liver to be effective. Special attention should be paid to these changes. The reduction of liver metabolism and detoxification functions in the elderly slows down the metabolism of some drugs, prolongs t1/2, prolongs the duration of action, increases toxic side effects, and increases liver damage. Therefore, when using such drugs in the elderly, the dosage should be adjusted appropriately.

Changes in the digestive system of the elderly may affect medication use:

(1) Be cautious when using any drug that may cause constipation.

(2) When using drugs that are mainly metabolized by the liver, the dosage should be adjusted if necessary.

(3) The ability of the elderly to metabolize theophylline decreases by about 45%.

(4) The metabolism of quinidine, cimetidine, tricyclic antidepressants, benzodiazepines, propranolol, lidocaine, and barbiturates is also significantly reduced, and their t1/2 is prolonged, making them easily accumulated in the body and causing toxic side effects.

In short, when elderly people use drugs that are mainly metabolized by the liver, the dosage should be reduced, generally to 1/2 to 1/3 of the dosage of young people, and the interval between medications should also be extended. Especially for elderly patients with existing liver disease, more attention should be paid to the medication time and interval between medications. When the respiratory system ages, the elastic fiber bundles around the alveolar tubules of the elderly become thinner, which reduces the elastic recovery performance of the lungs, reduces compliance and increases residual volume, and reduces arterial oxygen partial pressure; the lungs' clearance capacity and the ability to remove other environmental pathogens are reduced.

Elderly patients with blood system should be cautious when using drugs with adverse reactions of bone marrow suppression. After elderly patients take warfarin, its effects and adverse reactions are enhanced. Therefore, the dose should be reduced, and signs of bleeding (hematuria, occult blood in stool) and routine coagulation time should be observed during medication.

Immune system: Elderly people should pay attention to using drugs that enhance immune function.

Endocrine system

(1) Both insulin and oral hypoglycemic drugs can cause hypoglycemia in elderly patients. The central nervous system of the elderly is very sensitive to hypoglycemia. If it is not corrected in time, it can cause serious or permanent damage. Long-acting insulin preparations and long-acting chlorpropamide are the most serious and should not be used.

(2) The incidence of adverse reactions to glucocorticoids in the elderly is significantly increased, such as a greater susceptibility to peptic ulcers, bleeding, and perforation; osteoporosis, fractures, and even aseptic necrosis of the femoral head; delayed wound healing, and cataracts. Therefore, it is best not to use glucocorticoids in elderly patients, and if they must be used, the dosage should be reduced.

(3) Hormone replacement therapy is generally not recommended except for ovarian atrophy.

1. Others

(1) Tissue sensitivity: As people age, their body's sensitivity to drugs also changes. They are more sensitive to some drugs, and may even experience an overdose reaction at the usual dose, such as thyroxine and digitalis, which should be reduced. Some drugs are less sensitive, such as isoproterenol and propranolol, which should be increased.

(2) Drug tolerance: The tolerance of the elderly to drugs is reduced, and it is more obvious in women than in men. Usually, when a drug is used alone or in combination with a small amount of drugs, it can be tolerated. However, when multiple drugs are used in combination without reducing the dosage, adverse reactions and gastrointestinal symptoms are prone to occur. For example, a diuretic and a sedative may be well tolerated when taken separately, but orthostatic hypotension may occur if they are taken at the same time.

Distribution of drugs

As people age, the total amount of body fluid decreases, body fat increases, and plasma albumin levels decrease. These changes cause changes in the distribution of some drugs in the body, such as:

(1) It makes it easier for fat-soluble drugs to be distributed to the peripheral compartment, i.e., the peripheral fat, in the elderly, thus increasing the apparent distribution volume. For example, diazepam, phenobarbital, lidocaine, etc. have a long-lasting and enhanced effect. When taking fat-soluble drugs, the dosing interval should be extended.

(2) Water-soluble drugs tend to concentrate in the central compartment, reducing the apparent distribution volume and increasing the peak blood concentration. For example, digoxin, pethidine, acetaminophen, etc., the dose should be appropriately reduced.

(3) Due to the decrease in plasma albumin, the amount of drugs that are easily bound to albumin in the blood is reduced, thereby increasing the amount of free unbound drugs, that is, the blood drug concentration increases, which is easy to cause toxic reactions. For example, for sulfonamides, warfarin, pethidine, phenytoin sodium, etc., attention should be paid to reducing the dosage. In particular, when several drugs are used at the same time, they compete with each other for binding to albumin, which may increase the concentration of a certain drug in the free form in the blood, leading to poisoning.

Medication principles for the elderly

1. Benefit Principle

The benefit principle first requires that the elderly should have clear indications for medication. At the same time, drugs with definite efficacy and few toxic side effects should be selected. For example, for arrhythmias in the elderly, if there is no organic heart disease and there is hemodynamic disorder, long-term use of antiarrhythmic drugs can increase the mortality rate. Therefore, antiarrhythmic drugs should be used as little as possible. When choosing drugs, previous diseases and the functions of various organs should be taken into consideration. For some diseases that do not require treatment, do not rush to use drugs. For example, elderly people with insomnia and dreaminess can improve by avoiding factors that cause excessive excitement at night, including smoking and drinking strong tea.

2. Five drug principles

Many elderly people have multiple diseases. The average elderly person has 6 diseases and often takes multiple drugs, with an average of 9.1 diseases and up to 36 diseases. Excessive use of drugs not only increases the economic burden and reduces compliance, but also increases drug interactions. Data show that taking 2 drugs can increase drug interactions by 6%; taking 5 drugs can increase drug interactions by 50%; and taking 8 drugs can increase drug interactions by 100%. 40% of non-bedridden elderly people are at risk of drug interactions, of which 27% are at serious risk. The more drugs are used in combination, the higher the possibility of adverse drug reactions. Use fewer drugs, preferably less than 5, and prioritize treatment.

Pay attention when implementing the 5 drug principles:

① Understand the limitations of drugs. Many geriatric diseases do not have corresponding effective drug treatments. If excessive medication is used, the harm of ADR will be greater than the disease itself.

② Focus on the main contradiction and select the main drug treatment.

③ Select drugs with dual therapeutic effects: for example, for patients with hypertension and angina pectoris, beta-blockers and calcium antagonists can be used; for patients with hypertension and prostatic hypertrophy, alpha-blockers can be used.

④Pay attention to non-drug treatment.

⑤ Reduce and control the intake of tonic medicines: For cases of mild indigestion, poor sleep, etc., you can avoid taking medicines as long as you pay attention to food hygiene and avoid emotional fluctuations.

3. Small dose principle

The dosage for the elderly is 3/4 of the adult dosage as stipulated in the Chinese Pharmacopoeia; generally, 1/4~1/3 of the adult dosage is used at the beginning. The elderly should start with a small dose and gradually reach the optimal dosage suitable for the individual. Some scholars have proposed that starting from the age of 50, the dosage should be reduced by 1% compared with the adult dosage for each additional year. The dosage for those aged 60~80 should be 3/4 of the adult dosage, and 2/3 of the adult dosage for those aged 80 and above. Only when the dosage is kept at the lowest effective dosage can it be the optimal dosage for the elderly.

4. Timing Principles

The timing principle is to choose the best time to take the medicine. According to the principles of chronobiology and chronopharmacology, the most appropriate time to take the medicine is selected for treatment to improve the efficacy and reduce toxic side effects.

5. Principles of Suspension of Medication

Elderly people should be closely observed during medication. Once new symptoms appear, they should be considered to be adverse drug reactions or disease progression. In the former case, the drug should be discontinued, while in the latter, the drug should be increased. Therefore, suspending medication is one of the simplest and most effective intervention measures in modern geriatrics.

Precautions for medication in the elderly

(1) Medication selection must be based on a clear diagnosis and drug abuse must be strictly prevented.

(2) When medication is necessary for treatment, the number of different drugs should not be too large.

(3) When medication is necessary for treatment, the smallest effective dose should be selected.

(4) For patients with poor liver and kidney function, appropriate dosage adjustments should be made to the drugs used. It is best to perform blood drug concentration testing and implement individualized dosing.

(5) During treatment, the appropriate dosage form should be selected based on the characteristics of individual elderly patients.

(6) During treatment, the dosage should be adjusted in a timely manner, and the drug should be changed or discontinued according to the patient's condition.

(7) Elderly patients should avoid abusing tonic medicines.