ABSTRACT Drug Interactions is main issue of Health care system. This study was conducted to identify the nature and rate of occurrence of drug-drug interaction in prescriptions dispensed at retail pharmacies in Hyderabad, Pakistan. In this study the total 723 handwritten prescriptions were collected and from that only 630 clearly written prescription containing two or more than two medications were selected for analysis. Drug-drug interactions (DDIs) were detected by using the specially designed drug interaction checkers and detected interactions further confirmed by the Thomson Micromedex Health Care Series 2, British national formulary 63, Stockleys Drug Interaction checker. Out of total 630 prescriptions, 164 prescriptions (i-e 26%) of all the prescriptions contained 233 drug-drug interactions. Interactions then categorized on the basis of severity. On the basis of severity from the total 233 interaction, 26 (11%) of total interactions were of major type, 134 (58%) of total interactions were of moderate type and remaining 73 (31%) interactions were of minor type. Our study resulted that the prescriptions dispensed at retail pharmacies contained a high rate of drug-drug interactions. So an appropriate surveillance system must be implemented, physician and pharmacist must remain vigilant in investigation of drug-drug interactions to prevent adverse drug reaction

Abdullah Dayo

Hina Saleem

Imran Suheryani

Marvi Baloch

Muhammad Ali Ghoto

Muhammad Younis Laghari

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*Corresponding Author Address: Imran Suheryani, Department of Pharmaceutics Faculty of Pharmacy University of Sindh Jamshoro, 
Pakistan; e-mail: suheryaniimran@yahoo.com 
World Journal of Pharmaceutical Sciences 
ISSN (Print): 2321-3310; ISSN (Online): 2321-3086 
Published by Atom and Cell Publishers © All Rights Reserved 
Available online at: http://www.wjpsonline.org/ 
Original Article 
 
Evaluation of drug-drug interactions in the prescription dispensed at retail pharmacies 
 
Imran Suheryani
1*
, Muhammad Ali Ghoto
1
, Abdullah Dayo
1
, Hina Saleem
2
, Muhammad 
Younis Laghari
3
, Marvi Baloch
1
  
 
1
Department of Pharmaceutics, Faculty of Pharmacy, University of Sindh Jamshoro, Pakistan 
2
Dow College of Pharmacy, Dow University of Health Sciences, Karachi 
3
Department of Fresh water biology and Fisheries University of Sindh Jamshoro 
 
Received: 07-04-2014 / Revised: 22-04-2014 / Accepted: 24-05-2014 
 
ABSTRACT 
 
Drug Interactions is main issue of Health care system. This study was conducted to identify the nature and rate 
of occurrence of drug-drug interaction in prescriptions dispensed at retail pharmacies in Hyderabad, Pakistan. In 
this study the total 723 handwritten prescriptions were collected and from that only 630 clearly written 
prescription containing two or more than two medications were selected for analysis. Drug-drug interactions 
(DDIs) were detected by using the specially designed drug interaction checkers and detected interactions further 
confirmed by the Thomson Micromedex Health Care Series 2, British national formulary 63, Stockleys Drug 
Interaction checker.  Out of total 630 prescriptions, 164 prescriptions (i-e 26%) of all the prescriptions contained 
233 drug-drug interactions. Interactions then categorized on the basis of severity. On the basis of severity from 
the total 233 interaction, 26 (11%) of total interactions were of major type, 134 (58%) of total interactions were 
of moderate type and remaining 73 (31%) interactions were of minor type. Our study resulted that the 
prescriptions dispensed at retail pharmacies contained a high rate of drug-drug interactions. So an appropriate 
surveillance system must be implemented, physician and pharmacist must remain vigilant in investigation of 
drug-drug interactions to prevent adverse drug reaction. 
 
KEY WORDS: Drug Interactions, Prescription, Retail Pharmacy, Adverse drug Reaction, Synergism, 
Antagonism, Idiosyncratism 
 
 
INTRODUCTION 
 
Drug to drug interaction (DDIs) are defined as 
“The change in the effects of one or more 
concurrently administered medicines [1,2] or 
“effects of one drug are changed by another drug is 
called as drug-drug interactions”. Or “simply we 
can say drug interactions occur when drugs fight 
with each other and deviate from the targeted 
aims.” Chances of drug-drug interaction could 
increase in situation when concomitant use of many 
drugs is obligatory for a patient suffering from 
more than one disease [3]. The result of such drug-
drug interaction could appear as synergism, 
antagonism, or idiosyncratism [4] and could cause 
an increase in the effects of drugs to the level of 
toxicity and can lead to harmful results or they can 
inhibit the effects of the drug and there will be loss 
of therapeutic benefits [5]. Therefore pharmacist is 
a person who can play an important role to reduce 
the risk of drug-drug interactions, particularly in 
cases when drugs have small margin of activity or 
narrow therapeutic index [6]. Drug –drug 
interaction is the main issue in drug therapy. It may 
results in either increased or decreased efficacy, in 
treatment failure or in increased medication toxicity 
[7]. A physician may unintentionally prescribe 
improper combination which may result in less 
effects and more adverse drug reactions [8]. 
Patients visiting several physicians (who are 
prescribing less appropriate combinations) of the 
drugs due to unawareness of each other, the 
outcome of the therapy may be negatively 
influenced [9]. Concurrent use of prescriptions and 
non-prescription drugs or presence of certain 
disease such as kidney failure may increase the 
probability of drug interactions  
 
Mechanisms of Drug interactions: Mechanisms 
of drug interactions may be quit varied and 
Imran et al., World J Pharm Sci 2014; 2(6): 545-548 
546 
 
complex, therefore it is most essential to 
understand the mechanism by which drug 
interaction occurs, and that will be valuable to 
overcome the situation and to deal with the 
problems.  
 
Generally for convenience mechanism of drug 
interactions are divided into two classes.  
 
a) Pharmacokinetic drug interactions: (The  
delivery of drug to its site of action is altered by 
second drug).The interactions in which one drug 
(precipitant drug) changes the absorption, 
distribution, metabolism, or excretion of second 
drug (the object drug) with resultant change in the 
plasma concentration of second drug. Simply 
pharmacokinetics drug interactions are those which 
will affect the processes by which drugs are 
absorbed, metabolized, distributed, and excreted. 
Due to changes in above mentioned 
pharmacokinetic processes there will be 
fluctuations in plasma drug concentration and also 
alteration in delivery of drug to site of action. 
  
b) Pharmacodynamic drug interactions: (The 
response of the drug target is modified by a second 
drug). In Pharmacodynamic drug interaction the 
actions of one drug is altered by the presence of 
another drug at receptor site or site of action. 
Sometimes the drugs will directly come in 
competition for specific receptors (eg. beta-
blockers such as propranolol and beta-2 agonists 
like salbutamol). These interactions are much less 
easy to classify clearly as compare to 
pharmacokinetic drug interactions. 
Pharmacodynamic drug interaction involve 
additive (1+1= 2), potentiating (0+2=2), synergistic 
(1+1 =3) and antagonistic (1+1=0) affects at the 
level of receptors. 
 
MATERIAL AND METHOD 
 
Collection of Data: In this study data was 
collected through primary source from different 
retail pharmacies in various regions with the 
objective to evaluate the drug-drug interaction in 
the prescription dispensed at retail pharmacies.    
 
Selection of data: Prescriptions which were 
collected in data collection phase afterwards those 
prescriptions were sorted out for selection of data 
for further analysis. Some of the prescriptions were 
confused and not readable because collected 
prescriptions were hand written by the prescribers. 
Hence, only the prescription which had no any 
confusion in reading and containing two or more 
than two medications were selected for the analysis 
of drug- drug interactions.  
 
Methods of analysis: For analysis of drug-drug 
interactions the clearly written prescription which 
containing more than one medication were 
selected. After selection of appropriate 
prescriptions for analysis, general skills, practices, 
and keen interpretation is used in this study. 
 
All prescriptions containing two or more than two 
medications were screened for drug-drug 
interactions (DDIs). Drug-drug interactions (DDIs) 
were detected by using the specially designed drug 
interaction checkers within the 
www.medscape.com &  www.uptodate.com 2012 
data base and the detected interactions further 
confirmed by Thomson Micromedex Health Care 
Series 2012, British national formulary 63, 
Stockleys Drug Interaction checker and AHFS drug 
information 2012. 
 
Drug-drug interactions (DDIs) were categorized 
into three categories as follows 
a) Major : In the major interactions there is 
possibility of death and or medical 
intervention is necessary to minimize or 
prevent harmful outcomes  
b) Moderate: In the moderate interactions 
there is possibility of deterioration of 
patients condition and there may need of 
amendment of therapy 
c) Minor: In the minor interactions there is 
possibility of slight effects which will not 
weaken therapeutic outcomes, so there will 
be no necessitate of major change in 
therapy  
Major, Moderate and Minor interactions 
were further analyzed statically by using 
the Microsoft excess® Microsoft excel® 
and SPSS version 17.0 for representing the 
results in the form of Graphs and tables. 
 
RESULTS 
 
Total prescription collected: Total 726 
prescriptions were collected for this study, Out of 
which 81(11%) of total prescriptions contained 
single medication, 15 (02%) of total prescription 
were confused/unreadable and 630 (87%) of total 
prescription were those which contain two or more 
than two medication.  
 
Proportion of prescription with or without 
interactions: 630 clearly written prescriptions 
were analyzed for presence of drug-drug 
interactions. Out of total 630 prescriptions, 164 
prescriptions (i-e 26%) of all the prescription 
contained drug-drug interaction and remaining 466 
prescriptions (i.e. 74%) of all prescriptions were 
free from interactions and safe.  
Imran et al., World J Pharm Sci 2014; 2(6): 545-548 
547 
 
Total number of interaction in the screened 
prescriptions: Out of total 630 prescriptions 164 
prescriptions contained 233 drug-drug interactions. 
Now total 233 interactions were present in those 
164 prescriptions. From these all 164 prescription, 
111 prescriptions contains only one interaction, 37 
prescriptions contains two interaction and 16 were 
with three interactions. 
So there were 233 total interactions [111+ (37x2) 
=74+ (16x3) =48] interaction noted. 
Above equation results that 111 prescriptions with 
one interaction.    
And 37 prescriptions with two interactions so 37 
multiply by 2 it give 74 interactions. 
And 16 prescriptions with three interactions so 16 
multiply by 3 it give 48 interactions.  
So 111+74+48=233. 
 
Categories of interactions: All the interactions 
than categorized on the basis of severity. On the 
basis of severity from the total 233 interaction, 26 
interaction that is (11%) of total interactions were 
of major type, 134 interactions that is (58%) of 
total interactions were of moderate type and 
remaining 73 interactions that is (31%) of all 
interactions were of minor type.  
 
DISCUSSIONS  
 
This is first study of its nature in Hyderabad Sindh; 
the data was collected from the patients visiting the 
retail pharmacies for dispensing of drugs. So the 
data collection from the out patients had also 
unique importance, because after getting the drugs 
from the retail pharmacy there is no any check 
point to note down the Drug-Drug interactions. 
This Intension to collect the data from the retail 
pharmacies was due to the lack of pharmacist at the 
drug stores, other side it is clearly written in the 
drug laws and drug policies of Pakistan that drug 
store must be run by the pharmacist and no any 
other personnel is authorized to run the drug store.  
In this study data 726 prescription were collected, 
unfortunately some prescription were confused or 
not read able, so those confused prescription and 
the prescription containing only one medication 
were excluded and remaining 630 prescription were 
analyzed for the presence of drug-drug interactions.  
Current study exposed that the overall occurrence 
of drug-drug interactions was about 26%. In the 
various previous studies it was recorded that 4.1%, 
22%, 23% and 28% [10,11,12,13,14]. 
 
Our findings are matching with some previous 
studies in the different regions of the world, but 
little bit higher than the other studies due to the 
differences in prescribing pattern and also due to 
lacking of pharmacist for the health care system in 
this region. In our study all screened interactions 
were classified into three categories. Major (these 
interactions may prove fatal and may require 
medical intervention to prevent or to mitigate 
injurious outcomes). Moderate (these interactions 
may cause worsen the patient’s condition and or 
need in alteration in therapy. Minor (the minor 
interactions cause slight change in effects which 
will not deteriorate therapeutics outcomes, so there 
will be no need of major amendment in therapy. 
The occurrence of major drug-drug interactions 
was 4.9% of total prescription or 11% of entire 
drug interactions. And the incidence of the 
moderate interactions was 22.8% of total 
prescription or 58% of entire drug-drug 
interactions, whereas the prevalence of minor drug-
drug interactions was 31% 0f the total interactions. 
These findings show high drug-drug interactions as 
compare to the number of studies performed in 
other countries. The reason may be due to lacking 
of a consistent screening method for drug -drug 
interactions. 
 
It was observed that the rate of drug-drug 
interactions is more in case of Polypharmacy and it 
is directly proportional to the number of 
prescriptions or number of medications prescribed 
to a patient. As there will be increase in the number 
of medication so there will be increase in the 
chances of drug-drug interactions [15].  
 
From the total interactions obtained, majority of the 
drug interaction were of moderate severity, second 
number interaction were of minor severity and less 
number of drug interaction were of major severity. 
 
CONCLUSION 
 
The main objective of this study was to evaluate 
the drug-drug interactions in the prescriptions 
because drug-drug interaction may cause adverse 
drug response. Results of the present study indicate 
that prescriptions dispensed at retail pharmacies in 
district Hyderabad Sindh contain a high rate of 
drug-drug interactions. It was also observed that 
prescriptions with multiple numbers of medicines 
contained more interactions; it means the rate of 
drug-drug interactions is in a straight line to the 
number of medicine in a prescription. Our study 
findings suggest the physicians to remain careful in 
prescribing medicines, and also the pharmacist to 
remain vigilant in investigation of drug-drug 
interactions and make suitable adjustment in drug 
therapies to protect the patient from adverse effects.  
Further, there should be availability of pharmacist 
in health care systems and also in drug stores to 
assess the drug-drug interactions to reduce the risk 
of adverse consequences due to drug interactions.
  
 
Imran et al., World J Pharm Sci 2014; 2(6): 545-548 
548 
 
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Evaluation of drug-drug interactions in the prescription dispensed at retail pharmacies

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Evaluation of drug-drug interactions in the prescription dispensed at retail pharmacies

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