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Adverse Drug Reaction Probability Scale (Naranjo)

What is Naranjo - ADR Probability scale

 

The Naranjo Algorithm, or Adverse Drug Reaction Probability Scale, is a method by which to assess whether there is a causal relationship between an identified untoward clinical event and a drug using a simple questionnaire to assign probability scores.

Adverse Drug Reaction Probability Scale (Naranjo) in Drug Induced Liver Injury

This scale was developed to help standardize assessment of causality for all adverse drug reactions and was not designed specifically for drug induced liver injury. The scale was also designed for use in controlled trials and registration studies of new medications, rather than in routine clinical practice. Nevertheless, it is simple to apply and widely used. Many publications on drug induced liver injury mention results of applying the ADR Probability Scale.

The ADR Probability Scale consists of 10 questions that are answered as either Yes, No, or “Do not know”. Different point values (-1, 0, +1 or +2) are assigned to each answer. A simplified version of the 10 questions is provided below:

1.    Are there previous conclusive reports of this reaction?

2.    Did the adverse event appear after the drug was given?

3. Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given?

4.    Did the adverse reaction reappear upon read ministering the drug?

5.    Were there other possible causes for the reaction?

6.    Did the adverse reaction reappear upon administration of placebo?

7.   Was the drug detected in the blood or other fluids in toxic concentrations?

8.  Was the reaction worsened upon increasing the dose? Or, was the reaction lessened upon decreasing the dose?

9. Did the patient have a similar reaction to the drug or a related agent in the past?

10. Was the adverse event confirmed by any other objective evidence?


The actual ADR Probability Scale form and instructions on how it is completed are provided below. Total scores range from -4 to +13; the reaction is considered definite if the score is 9 or higher, probable if 5 to 8, possible if 1 to 4, and doubtful if 0 or less.

 

While this scale includes all of the usual features that are important in assessing causality, the scale is not weighted for the most critical elements in judging the likelihood of drug-induced liver injuries, such as specific time to onset, criteria for the time of recovery, and list of critical diagnoses to exclude, making the scale of limited use in assessing hepatotoxicity. The Naranjo scale also relies upon testing for drug levels, which is rarely helpful in idiosyncratic drug-induced liver disease. Finally, the scale was designed for use in clinical trials, and points are subtracted if the reaction


reappears with the administration of a placebo, which does not apply to the usual case of drug-induced liver disease. Direct comparisons to the RUCAM system have shown that the ADR Probability Scale is easier to apply, but has less sensitivity and specificity in assigning causality to cases of drug-induced liver injury.



According to the score Adverse Drug Reaction is categorized  into four categories :

Total score:-

·     >9 indicates definite ADR

·     5-8 indicates probable ADR

·     1-4 indicates possible ADR

·     0 indicates doubtful ADR

 

References :

https://www.google.com/url?sa=t&source=web&rct=j&url=https:// www.ncbi.nlm.nih.gov/books/NBK548069/&ved=2ahUKEwjN_- ST1bj8AhWD53MBHTGWAUcQFnoECB8QAQ&usg=AOvVaw00UiSs8U

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Written by:- Shivani Kumari 
Qualification:- B.PHARM 
Student ID:- 209/1222

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