Identifying drug-related illness in the elderly
bg Robert E Vestal
Since geriatric patients take more drugs than younger ones, it's not surprising they suffer more adverse effects. But how do you differentiate an adverse effect from another disorder that may mimic it?
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r ln rne eroeny can Pose a spectal
challenge. Though the potential for adverse
Multiple illness is the rule, rather dru.g reactions varies among aged in- than the exception, among geriatric dividuals, certain age-related somatic patients, and'with multip"le" illness a.nd physiologic changes that affect c o m e m u l t i p l e m e d i c a t i o n s a n d t h e d r u g d i s t r i b u t i o n , h e p a t i c possibility of confusing dosages and metabolism, and renal excretion dic- drug interactions. tate that we rule out toxicity in symp-
Many geriatric patients see more tomatic geriatric patients.
than one doctor and may be taking Drug distribufion. Distribution, the two or more drugs of the same type process by which drugs are delivered or with similar side effects. to various sites in the body, depends
Antidepressants, antipsychotic on the proportions of body fat, total agents, antihistimines, and non- body water, and lean mass.
prescription "cold" remedies and Aqain. there are variations: total sedative preparations, for example, bodi water, both in absolute terms all have anticholingergic properties. and as a percentage of body weight, The effects, which may be ad- is usually reducedin elderly people, ditive, produce dry mouth, blurred vi- while body fat tends to increase.
sion, constipation, urinary retention, The effect of these changes is to and neuropsychiatric symptoms. . reduce the proportion of leln body Taken injudiciously, over.the- mass pe*nit 6f total body weighi.
counter drugs by themselves may Such changes may affect blood create problems; elderly. people, levels of g"eriatric iatients taking more so than younger patients, are drugs regufiily, especialty obese and apt to rely on them as cure-alls. for emiciate-d palients.
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associate with the aging process -
forgetfulness, weaknlss-, confusion, .ln emaciated patients, with reduc- tremor, anorexia, and anxiew. (Table ed total body water, such water solu-
1). ble drugs as antipyrine and ethanol
can concentrate at toxic levels.
ln addition. albumin levels are reduced in elderly persons. For drugs that are protein-bound, the reduced albumin results in an increase in the amount of free drug concentrate in the plasma and subsequent diffusion ,into body tissues where sites of ac-
tion are located or into the liver and kidneys for elimination.
This is particularly true when renal failure results in low protein binding of a drug such as phenytoin. Even though the total plasma level may be in the low therapeutic range, a con- siderable amount of free drug may be available.
Increasing the dosage could result in an adverse reaction. Table 2 lists therapeutic levels of drugs. Levels above this range can cause toxicity.
Hepatic metabolism. Liver mass represents 2,5 percent of body weight until middle age, when it becomes relatively and progressively smaller. Studies indicate that the decrease in size is accompanied by altered metabolic capacity for some drugs, which, in turn, results in a pro- longed half-life and the possibility of drug accumulation and toxicity.
Renal excretion. Renal function decreases as much as 50 percent from ages 20 to 90, with an average
30 Family Practice - April 1982
Identifying drug-relatedillness in the elderly
decline of about 35 percent. Thus, drugs that are eliminated by the kidneys, such as digoxin and the aminoglycosides, may reach toxic levels in the presence of reduced renal function.
Nutrition and enuironmental fac- tors. In addition to age-related physiologic changes, the geriatric pa- tient's nutritional status may affect drug metabolism. With some drugs, such as antipyrine and theophylline, a low-protein/high-carbohydrate diet is associated with a longer half-life.
B e c a u s e o f s o c i o e c o n o m i c c i r - cumstances, many elderly people h a v e n u t r i t i o n a l l y p o o r d i e t s . Although ouert protein malnutrition is relatiuelg uncommon, Iook for signs of uitamin defictencg as an in- dication that the geriatic patient mag haue problems In drug metabolism.
Take a drug history
Often, it is not physiologic or metabolic changes that account for toxic reactions in elderly patients, but simply the fact that they're taking too much of a drug or too many drugs.
Alwags reuiew a geriatric patient's drug historg when he comes in with a complaint. Think about possible aduerse reaclions and queslion the patient to determine if his sgmptoms
coincide with a drug reaction. While a printed form may do for Younger patients, the elderlY Patient maY need some memory jogging, so it's best to conduct the history on a face- to-face basis. The patient may forget the name of a drug - if, in fact, he ever knew it - but he'llbe able to tell you about his "high'blood'pressure pills" or "those pills I bought at the chemist for my constiPation."
It may be necessary to have a relative confirm the report. Find out what prescription drugs the patient is taking, what the dosage is, and how long he's been taking the drugs. lf the p a t i e n t o r h i s r e l a t i v e c a n n o t iemember what drugs were prescrib' ed by another PhYsician, have Your assistant phone the doctor's office.
Find out r.uhen the patient takes his medication. Is he following the prescribed regimen, or does he take his pills all at once? Ask about non' prescription medications.
Again, the Patient maY not be able to remember sPecific names, but
IIRUG ILLNES$ IN THE ELDEffLY
.TABLE I,,
orug gmup; hesanting sympioms that srisgssl to.xicity'
3 2 Family Practice - April 1982
Identifying drug-related illness in the elderly
through careful questioning you can learn whether he's in the habit of tak- ing laxatives, unusual amounts of vitamins, aspirin or aspirin-containing drugs, or other over-the-counter agents, such as sleeping pills, an- tacids, or cold remedies that can in- terfere with the absorption of some drugs or exaggerate their effects.
C o l d r e m e d i e s c o n t a i n i n g a n - t i h i s t i m i n e s , f o r e x a m p l e , h a v e sedative qualities that may enhance the effects of tranquilizers. Be sure to ask about drinking and smoking habits; chronic alcohol consumption and cigarette smoking can stimulate the metabolism of some drugs.
The physical examination
While the diagnosis of drug-related illness depends on an accurate history and appropriate laboratory tests, the physical may give you some important clues. Check for postural hypertension. Examine the skin for rashes indicative of drug hypersensitivity.
In patients taking anticoagulants, look for hematomas or hemoar- throses, both of which signal an overabundance of free drug.
Confirmatory tests
Have patients with abdominalpain perform an occult.blood test to deter.
mine possible bleeding from aspirin o r a n o t h e r n o n s t e r o i d a l a n t i . inflammatory drug.
Prothrombin time more than two or two-and-one-half times control in- dicates a need to lower the dose of warfarin. A low serum potassium c o n f ir m s
hypokalemia.
d i u r e t i c - i n d u c e d An ECC will tellyou if digitalis use has caused arrythmias. Look for an increase in serum creatinine or a decrease in the 14.hr creatinine clearance test as an indication of n e p h ro t o x i c i t y f r o m aminoglycosides.
Finally, plasma levels of some of the drugs listed in Table 2 will also help you confirm suspected drug tox.
icity. n
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tions, there are few effective agents for the management of serious fungal (mycotic) infections. There is no oral preparation with this spectrum of ac- tivity and the other systemic an- timycotics have unacceptable side.
effects and can be dangerously toxic.
Intensive clinical trials and more than a year of widespread usage have shown Nizoral to lack significant side.
effects or toxicity. In a survey of i 361 patients, the most frequently r e p o r t e d s i d e - e f f e c t s w e r e n a u s e a / v o m i t i n g ( 3 % ) , p r u r i t u s ( 7 , 7 % ) o r a b d o m i n a l p a i n ( 1 , 3 % ) . AII other reported reactions occured with a frequency of less than 7% and many as single instances only.
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Family Practice - April 1982 33
