Risk of potential drug-drug interactions among Brazilian elderly: a population-based, cross-sectional study.
BACKGROUND
Drug-drug interactions (DDIs) are one of the main causes of adverse reactions related to medications, being responsible for up to 23% of hospital admissions. However, only a few studies have evaluated this problem in elderly Brazilians.


OBJECTIVE
To determine the prevalence of potential DDIs (PDDIs) in community-dwelling elderly people in Brazil, analyse these interactions with regard to severity and clinical implications, and identify associated factors.


METHODS
A population-based cross-sectional study was carried out involving 2143 elderly (aged >or=60 years) residents of the metropolitan area of Sao Paulo, Brazil. Data were obtained from the SABE (Saúde, Bem estar e Envelhecimento [Health, Well-Being, and Aging]) survey, which is a multicentre study carried out in seven countries of Latin America and the Caribbean, coordinated by the Pan-American Health Organization. PDDIs were analysed using a computerized program and categorized according to level of severity, onset, mechanism and documentation in the literature. The STATA software statistical package was used for data analysis, and logistic regression was conducted to determine whether variables were associated with PDDIs.


RESULTS
Analysis revealed that 568 (26.5%) of the elderly population included in the study were taking medications that could lead to a DDI. Almost two-thirds (64.4%) of the elderly population exposed to PDDIs were women, 50.7% were aged >or=75 years, 71.7% reported having fair or poor health and 65.8% took 2-5 medications. A total of 125 different PDDIs were identified; the treatment combination of an ACE inhibitor with a thiazide or loop diuretic (associated with hypotension) was the most frequent cause of PDDIs (n = 322 patients; 56.7% of individuals with PDDIs). Analysis of the PDDIs revealed that 70.4% were of moderate severity, 64.8% were supported by good quality evidence and 56.8% were considered of delayed onset. The multivariate analysis showed that the risk of a PDDI was significantly increased among elderly individuals using six or more medications (odds ratio [OR] 3.37) and in patients with hypertension (OR 2.56), diabetes mellitus (OR 1.73) or heart problems (OR 3.36).


CONCLUSIONS
Approximately one-quarter of the elderly population living in Sao Paulo could be taking two or more potentially interacting medicines. Polypharmacy predisposes elderly individuals to PDDIs. More than half of these drug combinations (57.6%, n = 72) were part of commonly employed treatment regimens and may be responsible for adverse reactions that compromise the safety of elderly individuals, especially at home. Educational initiatives are needed to avoid unnecessary risks.
Secoli
Silvia-Regina
SR
Nursing College, University of São Paulo, São Paulo, Brazil.
Figueras
Albert
A
Lebrão
Maria Lúcia
ML
de Lima
Fernão Dias
FD
Santos
Jair Licio Ferreira
JL
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D017723:Drug Utilization Review; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D006801:Humans; D008297:Male; D019338:Polypharmacy; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D049993:Sodium Chloride Symporter Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000009:adverse effects / Q000627:therapeutic use
D000806:Angiotensin-Converting Enzyme Inhibitors; D049993:Sodium Chloride Symporter Inhibitors; D049994:Sodium Potassium Chloride Symporter Inhibitors
Ann Emerg Med. 2001 Dec;38(6):666-71
11719747
Arch Intern Med. 2005 May 23;165(10):1095-106
15911722
JAMA. 1997 Jan 22-29;277(4):301-6
9002492
Lancet. 2007 Jul 14;370(9582):185-191
17630042
Drug Saf. 2001;24(3):167-82
11347721
Ann Pharmacother. 2002 Sep;36(9):1331-6
12196047
J Am Geriatr Soc. 1996 Aug;44(8):944-8
8708305
Arch Intern Med. 1997 Oct 13;157(18):2089-96
9382665
Cardiol Clin. 2001 May;19(2):215-34, v
11407107
Drugs Aging. 1998 Jun;12(6):485-94
9638396
JAMA. 1998 Apr 15;279(15):1200-5
9555760
Ann Emerg Med. 1981 Dec;10(12):627-30
7305093
Drugs Aging. 2005;22(9):767-77
16156680
Res Social Adm Pharm. 2007 Dec;3(4):426-37
18082877
Arch Intern Med. 1995 Oct 9;155(18):1949-56
7575048
Acad Emerg Med. 2002 Nov;9(11):1162-7
12414465
J Clin Pharm Ther. 2005 Oct;30(5):471-7
16164494
Am Fam Physician. 2000 Mar 15;61(6):1745-54
10750880
J Emerg Med. 2002 Feb;22(2):159-62
11858920
Eur J Clin Pharmacol. 2003 Mar;58(11):773-8
12634985
Ann Pharmacother. 2002 Nov;36(11):1675-81
12398558
Rev Esc Enferm USP. 2008 Dec;42(4):706-14
19192905
Acad Emerg Med. 2000 Nov;7(11):1321-9
11073486
J Cardiovasc Pharmacol. 1995 Jul;26(1):114-8
7564350
Ann Pharmacother. 1993 Jul-Aug;27(7-8):832-40
8364259
Fam Pract. 1991 Sep;8(3):234-6
1822974
Am J Hosp Pharm. 1992 Jan;49(1):90-6
1570873
J Clin Epidemiol. 1991;44(8):823-30
1941035
JAMA. 2003 Apr 2;289(13):1652-8
12672733
Pharm World Sci. 1995 Sep 22;17(5):152-7
8574210
Am J Health Syst Pharm. 2005 Oct 1;62(19):1983-91
16174833
Crit Rev Oncol Hematol. 2003 Nov;48(2):133-43
14607376