An Investigation of Drug Interactions in Hospital Pharmacy Prescriptions

Authors

Abstract

Drug therapy is a complex and important process and because of the importance of drug interactions, especially in in-patients, accompanying problems and obstacles would exist as a result of concomitant use of drugs in these patients. For this purpose 3130 prescription order forms from Bou-Ali hospital were collected and all potential drug interactions presentwere extracted and evaluated in terms of significance, severity, documentation and onset.

Interactions were divided into 5 groups based on their significance, with group 1 being the most important and group 5 the least important.

Most interactions observed belonged to groups 4 and 5, accounting for 68.5% of all interactions.Group 1 interactions only accounted for 7.8% of all interactions observed.

When considering the onset of interactions, the most dominant type (55.8% of all interactions) were the slow-occurring ones. In terms of the severity, most interactions (47.2%) were of the medium (moderate) type. Strong (severe) interactions only accounted for 8.2% of all interactions.

Finally, in terms of the documentation of interactions, the most prevalent type were the probable ones, accounting for 56.8% of all interactions observed. Definite interactions only accounted for 4.3% of all interactions.

Keywords


An Investigation of Drug Interactions in Hospital Pharmacy Prescriptions

Iranian Journal of Pharmaceutical Research 2002, 1: 15-19
Received: February 2002
Accepted: July 2002

Original Article

An Investigation of Drug Interactions in Hospital Pharmacy Prescriptions

Giti Hajebi*, Seyed Alireza Mortazavi

Department of Pharmaceutics, School of Pharmacy, Shaheed Beheshti University of Medical Sciences and Health Services, Tehran, Iran.
* ghajebi@yahoo.com

Abstract

Drug therapy is a complex and important process and because of the importance of drug interactions, especially in in-patients, accompanying problems and obstacles would exist as a result of concomitant use of drugs in these patients. For this purpose 3130 prescription order forms from Bou-Ali hospital were collected and all potential drug interactions present were extracted and evaluated in terms of significance, severity, documentation and onset.

Interactions were divided into 5 groups based on their significance, with group 1 being the most important and group 5 the least important.

Most interactions observed belonged to groups 4 and 5, accounting for 68.5% of all interactions.Group 1 interactions only accounted for 7.8% of all interactions observed.

When considering the onset of interactions, the most dominant type (55.8% of all interactions) were the slow-occurring ones. In terms of the severity, most interactions (47.2%) were of the medium (moderate) type. Strong (severe) interactions only accounted for 8.2% of all interactions.

Finally, in terms of the documentation of interactions, the most prevalent type were the probable ones, accounting for 56.8% of all interactions observed. Definite interactions only accounted for 4.3% of all interactions.

Keywords: Drug interaction; Hospital prescription; Prescription; Significance of interaction.

Introduction

Concomitant use of several drugs for a patient is often necessary for achieving a set goal or in cases when the patient is suffering from more than one disease. In these cases the chance of encountering drug - drug interactions could increase (1).

The term "drug interaction" is used when the effects of a drug in the presence of other drugs, food, beverages or environmental and chemical factors, alters (2).

The clinical output of such interactions could appear as antagonism, synergism or idiosyncratism (3).

In a study by Galley et al., it was found that from a total number of 160 patients in the internal ward, 221 cases of interaction exists, in which 24 were of the major type, 115 of the moderate type and 82 minor interactions. In addition it was found that the presence of certain diseases such as kidney failure, or the use of more than 6 drug items, could increase the probability of drug interactions (4).

In another study by Borda et al., drug interactions in the in-patients of various wards were studied. These interactions accounted for 22% of all cases of drug-drug interactions observed in the hospital (5).

Dipiro and Sislay found in another study that most interactions observed in hospital with patients undergone surgery is due to H2-blockers (especially cimetidine), digoxin and warfarin with the anesthetic drugs (6). Finally, Stanszex and Franklin found that drug interactions in out-patients amounts to 23% of all cases of drug interactions studied (7).

Therefore, because of the importance of drug - drug interactions, in this study attempts were made to investigate the occurrence and extent of drug interactions in the prescriptions of ICU, CCU, internal and infectious wards of Bou-Ali teaching hospital, Tehran, Iran.

Experimental

In this study the extent of occurrence and frequency of potential drug interactions were investigated based on the reference text "Drug Interaction Facts". This particular reference was used because of its extensive and unique classifications of drug interactions.

In this study a total number of 3130 prescriptions from in-patients of ICU, CCU, internal and infectious wards of Bou?Ali teaching hospital were examined during the first 6 months of 2000 and all the potential drug interactions present were extracted and classified in terms of significance, onset, severity and documentation.

Results

Among the prescriptions examined 3960 cases and 156 types of interaction were observed.

Table 1. A summary of prescriptions evaluated in various wards of Bou-Ali hospital.

Ward

Number of prescriptions

Number of interactions

Type of interactions

Number of prescribed drugs

Mean number of
drugs prescribed

CCU

400

598

80

40

5.0

ICU

380

342

58

32

5.7

Internal

1250

1763

151

58

4.4

Infectious

1100

1257

131

39

4.2

Table 1 shows the overall results obtained from assessing prescriptions of various wards. The overall results obtained in terms of significance, onset, severity and documentation are shown in Tables 2-5 and can be summarised as follows:

In terms of the significance, the most frequent interactions observed were of types 4 and 5 (the least important), with a total number of 2712 cases of interactions, accounting for 68.5% of the total number of interactions observed.

Table 2. Frequency distribution of 598 number of interactions ( 80 types) observed in the CCU ward of Bou-Ali hospital.

Parameter studied

Number of

Interactions

Percentage of interactions

Type of

Interactions

Percentage of interactions

Significance of interactions:

1.0

2.0

3.0

4.0

5.0

 

 

39

89

36

238

196

 

6.5

14.9

6.0

39.8

32.8

 

7

8

6

32

27

 

8.7

10.0

7.5

40.0

33.8

Onset of action:

Delayed

Rapid

 

 

193

405

 

32.3

67.8

 

40

40

 

50.0

50.0

Severity of interactions:

Major

Moderate

Minor

 

 

47

325

226

 

7.9

54.3

37.8

 

10

41

29

 

12.5

51.2

36.3

Documentation of interactions:

Established

Probable

Suspected

Possible

Unlikely

 

15

106

44

398

35

 

2.5

17.8

7.4

66.5

5.8

 

3

10

8

48

11

 

3.7

12.5

10.0

60.0

13.8

 

Table 3. Frequency distribution of 342 number of interactions ( 58 types) observed in the ICU ward of Bou-Ali hospital.

Parameter studied

Number of

interactions

Percentage of interactions

Type of

interactions

Percentage of interactions

Significance of interactions:

1.0

2.0

3.0

4.0

5.0

 

 

12

66

4

163

97

 

3.5

19.3

1.2

47.6

28.4

 

5

9

2

22

20

 

8.6

15.5

3.5

37.9

34.5

Onset of action:

Delayed

Rapid

 

 

149

193

 

43.5

56.5

 

29

29

 

50.0

50.0

Severity of interactions:

Major

Moderate

Minor

 

 

19

245

78

 

5.5

71.7

22.8

 

6

32

20

 

10.3

55.2

34.5

Documentation of interactions:

Established

Probable

Suspected

Possible

Unlikely

 

13

20

48

205

56

 

3.8

5.8

14.0

60.0

16.4

 

6

4

6

36

6

 

10.3

7.0

10.3

62.1

10.3

 

Table 4. Frequency distribution of 1763 number of interactions (151 types) observed in the internal ward of Bou-Ali hospital.

Parameter studied

Number of

interactions

Percentage of interactions

Type of

interactions

Percentage of interactions

Significance of interactions:

1.0

2.0

3.0

4.0

5.0

 

 

122

321

112

479

729

 

6.9

18.2

6.3

27.2

41.4

 

10

29

9

46

57

 

6.6

19.2

6.0

30.5

37.7

Onset of action:

Delayed

Rapid

 

1064

699

 

60.4

39.6

 

91

60

 

60.3

39.7

 

Severity of interactions:

Major

Moderate

Minor

 

 

163

792

808

 

 

9.3

44.9

45.8

 

 

 

13

77

61

 

 

8.6

51.0

40.4

Documentation of interactions:

Established

Probable

Suspected

Possible

Unlikely

 

95

268

168

1052

180

 

5.4

15.2

9.5

59.7

10.2

 

10

22

15

86

18

 

6.6

14.5

9.9

57.0

12.0

 

Table 5. Frequency distribution of 1257 number of interactions (131 types) observed in the infectious ward of Bou-Ali hospital.

Parameter studied

Number of

interactions

Percentage of interactions

Type of

interactions

Percentage of interactions

Significance of interactions:

1.0

2.0

3.0

4.0

5.0

 

 

134

277

36

229

581

 

10.7

22.0

2.9

18.2

46.2

 

6

27

5

37

56

 

4.6

20.6

3.8

28.2

42.8

Onset of action:

Delayed

Rapid

 

 

805

452

 

64.0

36.0

 

81

50

 

61.8

38.2

Severity of interactions:

Major

Moderate

Minor

 

 

98

507

652

 

7.8

40.3

51.9

 

10

67

54

 

7.7

51.0

41.3

Documentation of interactions:

Established

Probable

Suspected

Possible

Unlikely

 

48

251

138

595

225

 

3.8

20.0

11.0

47.3

17.9

 

7

19

11

76

18

 

5.3

14.5

8.4

58.0

13.8

 

With regards to the onset of action, the most dominant type of interactions were the delayed ones, with a total number of 2211 cases, representing 55.8% of the total number of interactions observed.

When considering the severity of interactions, moderate interactions were dominant, with a total number of 1869 cases, accounting for 47.2% of the total number of interactions observed.

Finally, in terms of the documentation of interactions observed, the most prevalent interactions were of the "possible" type, with a total number of 2250 cases, accounting for 56.8% of the total number of interactions. "Established" interactions only accounted for 4.3% of all interactions.

Discussion

Drug interaction is a very important issue in drug therapy, especially in pediatric and geriatric patients. In the earlier parts of this article (introduction) some of the results obtained by the other researcher have been mentioned. However, it should be noted that since the protocol for conducting these studies could be somewhat different from that of the present study, variation in the results obtained is expected.

Generally speaking the most prevalent type of interactions observed in our study are types 4 and 5, accounting for 68.5% of all interactions observed. This shows that in most cases the drugs prescribed for patients will not cause any serious or fatal interactions. Nevertheless, 7.7% of all interactions were due to type 1 interactions, meaning that patients life could be at risk and in such cases the physician and nursing staff should keep the patient under close surveillance. Furthermore, the infectious ward had the highest number of type 1 interactions, which is probably due to the nature of treatment and the need for combined drug therapy.

Regarding the onset of action, 55.8% were of the delayed type, which could take up to several days or weeks to occur, needing no immediate concern or medical intervention.

When considering the severity of interactions, 8.2% of all interactions were due to "major" interactions, and in such cases the life of patient could be threatened and immediate medical intervention is required. Furthermore, patients should be kept under close observation to prevent any complications.

In terms of the documentation of interactions observed, only 4.3% of all interactions were due to "established" interactions. It should be noted that proper monitoring of patients, a reduction in the dosage regimen, increasing the dosing intervals, etc. could help to reduce risks of severe drug interactions.

In fact the most important parameter to be considered is to find whether a drug could interact with other drugs, and try to find a way to encounter this problem.

In conclusion, it could be said that in this study drug interactions do not appear to cause a serious problem to the health of patient and process of drug therapy. However, further clinical studies are needed to be carried out in order to investigate the actual clinical occurrence of drug interactions.

Acknowledgement

The authors wish to thank Dr. V. Sedeghi for his assistance with this work.

References

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