Drug substitution/ therapeutic interchange (Abdal-e-Advia ) is an important facet of Unani medicine pharmacotherapy. It deals with principles, needs and related aspects of drug substitution or interchange of drugs for therapeutic purposes. Unani scholars have suggested substitutes of unavailable drugs merely on the basis of clinical observations.
Drug substitution or therapeutic interchange of drug (Abdaal-e- Advia) may be defined as use of an alternate drug in place of drug of choice. It is nothing but an alternate drug prescription at the time of unavailability of the drugs of choice. In other words drug substitution is replacement of one plant species by another in special circumstances. The new species is often of a completely different genus, but with similar properties and effects/ actions. Substitution of drugs (Abdaal-e- Advia) is an established and accepted practice in Unani system of medicine.
Substitution of Drugs/ therapeutic interchange of drugs (Abdaal-e- Advia) is a major challenge causing threat to the Unani medicine drug industry and to the research on commercial natural products.
Unani concept of drug substitution or therapeutic interchange (Abdaal-e- Advia) is based on similarity in action of drug, temperament and physical properties of drugs mainly botanicals, which are already established and need no further discussion. Increasing level of understanding of facts has given expositions favourable turn and last few decades have witnessed attempts to explicate classical concepts on new parameters, which have paved way for inclusion of scientific knowledge to discuss these concepts.
Beside, scientific studies have confirmed efficacy of many botanicals on phytochemical basis indicating that drugs having similar active constituents may exert similar pharmacological actions.
The concept of substitution prevailed ages back and in Unani medicine we can find this in the treatise of Razi (Rhazes 865–925 AD) and Ibn-e- Sina (980–1037 AD). There is a need to analyse these concepts with the present trend of substitution so that we can adopt the proper way.
Need for Substitution
Unani Concept of drug substitution (Abdal-e-Advia )
Unani medicine classical texts have introduced concept of Abdaal-e- Advia (Drug substitution/ therapeutic interchange) in ancient times in which in the absence of a desired first choice medicinal herb, classical Unani text recommends use of a functionally similar drug as its substitute.
As per the Unani concept of drug substitution/ therapeutic interchange (Abdaal-e- Advia), a rare or unavailable medicinal plant is substituted by a more readily available species.
Unani concept of therapeutic interchange, despite having immense practical aspect, has not been touched upon in a coherent way by most of the Unani scholars except Razi (Rhazes 865–925 AD) and Ibn-e- Sina (980–1037 AD), who took the concept plausibly and framed rules for alternate drug prescription at the time of unavailability of the drugs of choice.
Despite being vital, concept of drug substitution has not been talked about adequately by most of the Unani scholars.
Zakariya Razi (865–925 AD) is the only person who has dealt with the concept of Abdaal-e- Advia (Drug substitution/ therapeutic interchange) in detail. But, he has mentioned substitutes of 122 drugs in his book, Kitab-al-Abdal.
Avicena (Ibn-e- Sina) (980–1037 AD), another genius, has also suggested substitutes of single drugs in his book, the Canon of Medicine (Al Qanoon fil Tib). He has described substitutes of total 61 drugs from a long list of 781 drugs that have been described by him.
Unani drugs are substituted when they are endangered, costly, rare, banned or the procurement cumbersome. A drug is prescribed as a substitute only for a particular action, as the substitute could differ from main drug in other actions.
In classical Unani text there are frequent examples of substitute between drugs of different origins, e.g. a botanical origin drug can be substitute of an animal or mineral origin drug. Furthermore, if a fresh drug is in short of availability, inferior quality of the same may be used in increased dose to maintain efficacy. Similarly, if a particular part of a botanical is not available; other parts of the same botanicals may be used.
Criteria for Substitution
A drug to be considered as a substitute should fulfil the following criteria
Similarity in Action
As per the Unani concept, basis of substitution of drugs for therapeutic purposes are Yaksaniyat-e-afal (similarity in action) or both the drugs Exhibit similar therapeutic effects.
Similarity in temperament of drug
The next impotant criteria for therapeutic interchange of drug is Yaksaniyat-e-mizaj (similarity in temperament)
Similarity in external properties
Another important criteria for the substitution of drug is Yaksaniyat-e-zahiri khususiyat (similarity in physical properties /organoleptic characters) of main and substitute drugs. Accordingly, in case of non availability of intended drug, another drug having similar action or temperament or physical properties or any two or all is substantial for selection of a substitute.
Types of substitution of drug (Abdaal-e- Advia): It is mainly classified into three types
1. Badal-e-aqrab (closest substitution)
Badal (substitution of drug) may be closest substitution (Badal-e-aqrab ) in which both drugs are similar in action, origin, and type, e.g., substitute of natural borax is artificial borax.
2. Badal-e-qareeb (closer to substitution)
Closer to substitution (Badal-e-qareeb ) in which both drugs are similar in action and origin, like ammonium chloride is therapeutic interchange of natural borax.
3. Badal-e-bayed (remote substitution)
remote substitution (Badal-e-bayeed ) in which both drugs are similar in action only, e.g., natural borax is substitute of black mustard.
However, preference is given to similarity in action followed by origin and lastly type of drugs.
Othe Clessification of Substitution of drug (Abdaal-e- Advia): other classification of Substitution of drug (Abdaal-e- Advia) is as under.