This document discusses defined daily doses (DDDs) and provides formulas and examples to calculate antibiotic usage in DDDs per 100 patient admissions and per 1000 patient days. It defines a DDD as the assumed average maintenance dose per day for a drug's main indications. Examples are given to demonstrate calculating DDDs for cefoperazone/sulbactam, piperacillin/tazobactam, and polymyxin B based on antibiotic usage data, patient admission numbers, and patient days for three hospitals. Guidance is provided that 10 DDDs per 100 admissions or 10 DDDs per 1000 patient days generally indicates the drug was received by 10% or 1% of patients respectively.

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Rahela Ambaras Khan
Hospital Sungai Buloh

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 Defined Daily Dose (DDD) is the assumed average
maintenance dose per day for a drug used for its
main indications in adult.
 DDD is a unit of measurement and does not
necessarily reflect the recommended or prescribed
daily dose.

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 DDD assignments are designed solely to maintain a
stable system of drug consumption measurement,
which can be used to follow and compare trends in
the utilisation of drugs within and across
therapeutic groups.
 DDD has been approved by WHO for drug studies
and for comparisons independent of differences in
prices, preparation and quantity per prescriptions.
Guidelines for ATC Classification and DDD Assignment (WHO Collaborating Centre for
Drug Statistics Methodology 2006; www.whocc.no)

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Total Antibiotic Usage (Grams) for Adults Inpatient in a year = No of DDD’s per year
DDD* (from WHO)
For 100 Patient Admissions:
No of DDD’s per year X 100 = No of DDD’s per 100 admissions
No of adult patients warded
for that particular year
For 1000 Patient Days
No of DDD’s per year X 1000 =No of DDD’s per 1000 days
Total no of patient days for that
particular year
Formulas used are: -

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10. 1. Hosp. Q used 15,000 vials of Inj.
Cefoperazone/Sulbactam in 2009. No. of
patients admitted in 2009 was 40,000 and
average length of stay of adult patients
warded was 3.04 days.
Calculate the DDD per 100 patient-
admissions and DDD per 1000 patient-
days.
[DDD WHO for Cefoperazone, combination
= 4g]

11. Antibiotic Usage
in g for
adult
patients
in 2009
(a)
Defined Daily
Dose (DDD)
from WHO
(b)
No. of
DDD 's
per
Year
(a/b)
No. of
Adult
Pt
Admitt
ed in
2009
(c)
Total
No. of
Days for
Adult
Patient in
2009
(d)
Defined Daily Dose for Cefoperazone, Combinations
100 Pt-Admissions
No.of DDD's per year x 100
c
1000 Patient-Days
No.of DDD's per year x 1000)
d
Cefoperazone (500mg) /Sulbactam (500mg) Inj:
i) Cefoperazone 7, 500 g 4g 1, 875 40,000 121, 600 4.69 15.42
ii) Sulbactam
7, 500 g
1g

12. 2. Hosp. R used 10, 296 vials of Inj.
Piperacillin/Tazobactam in 2009. No. of
patients admitted in 2009 was 38, 500
patients and total no. of days adult
patients were warded was 170 000 days.
Calculate the DDD per 100 patient-
admissions and DDD per 1000 patient-
days.
[DDD WHO for Piperacillin & B-lactamase
Inhibitors, combination = 14g]

13. Antibiotic Usage
in g for
adult
patients
in 2009
(a)
Defined
Daily Dose
(DDD)
from WHO
(b)
No. of
DDD 's
per Year
(a/b)
No. of
Adult Pt
Admitte
d in
2009
(c)
Total
No. of
Days for
Adult
Patient
in 2009
(d)
Defined Daily Dose for Piperacillin and ß-lactamase
inhibitors
100 Pt-Admissions
No.of DDD's per year x 100
c
1000 Patient-Days
No.of DDD's per year x 1000)
d
Piperacillin (4g) /Tazobactam (500mg) Inj
i) Piperacillin
41,184g
14g
2, 941.71 38, 500 170, 000 7.64 17.30
ii) Tazobactam
5,148g

14. 3. Hosp. S used 80 vials of Inj. Polymyxin B
in 2009. No. of patients admitted in 2009
was 51, 409 patients and total no. of
days adult patients were warded was 237,
659 days.
Calculate the DDD per 100 patient-
admissions and DDD per 1000 patient-
days.
[DDD WHO for Poly B = 0.15g]

15. Antibiotic Usage
in g for
adult
patients
in 2009
(a)
Defined
Daily Dose
(DDD)
from WHO
(b)
No. of
DDD 's
per Year
(a/b)
No. of
Adult Pt
Admitte
d in
2009
(c)
Total
No. of
Days for
Adult
Patient
in 2009
(d)
Defined Daily Dose for Piperacillin and ß-lactamase
inhibitors
100 Pt-Admissions
No.of DDD's per year x 100
c
1000 Patient-Days
No.of DDD's per year x 1000)
d
Polymyxin B Inj (50mg or 5000, 000 iu/vial)
1mg = 10, 000 iu
Polymyxin B
4g
0.15g
26.67 51,409 237,659 0.05 0.11
How about Colistin?
DDD WHO for Colistin = 3MU
Make sure convert to MU usage before divided with WHO DDD
1 vial = 80 mg / 1, 000, 000 iu
1mg = 12, 500 iu

16.  10 DDD/100 Pt Adm
- 10% of pt admitted might get that drug in
that year
- 10DDD/1000 Pt Days
- - 1% of pt might receive a DDD of that drug
everyday
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17. THANK YOU
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