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          The information given in the general notices provides the basic guidelines for the interpretation and applications of the standards, tests, assays and other specifications of the Thai Herbal Pharmacopoeia. 

          In the text of the Thai Herbal Pharmacopoeia the word “Pharmacopoeia” means the Thai Herbal Pharmacopoeia.  The official abbreviation for the Thai Herbal Pharmacopoeia is THP.  An herbal material is not of the pharmacopoeial quality unless it complies with all the requirements of the relevant monograph.  The statements under the headings:  Description, Solubility, Cons tituents, Packaging and storage, Contra-indication, Warning, Precaution, and Additional information are not to be regarded as analytical requirements.  However, the macroscopic and microscopic descriptions under each monograph are important means for the identification of the drug and its corresponding origin. 

          Unless otherwise specified, the rules of the General Notices of the Thai Pharmacopoeia (TP) apply to the Thai Herbal Pharmacopoeia.

Monograph Nomenclature 

          A Thai name is adopted as the main title of each pharmacopoeial substance. It is transcribed to English following the Royal Institute’s official transliteration system¹ and printed with capital letters.  Subsidiary titles, where applicable, are other Thai name(s), Latin genitives of plants, English common name(s), and English synonym(s). 

          In the text, English common names are usually mentioned in place of the main titles. When the English common names are not available, the English names derived from the Latin genitives of plants will be used ins tead.  All titles (main and/or subsidiary) and names (synonyms as well as botanical names) are listed in the index.

Reference Substances

          Where a test or an assay calls for the use of a Reference Substance, the ASEAN Reference Substance or other recognized reference substances may be used.  The ASEAN Reference Substances are available from the Bureau of Drug and Narcotic, the Department of Medical Sciences, Nonthaburi, Thailand.

Authenticated Reference Specimens

          For the botanical evaluation of the crude drug samples, the herbarium specimen numbers of the corresponding plants provided in the text are taken from the Department of Medical Sciences Herbarium (DMSC), the Department of Medical Sciences, Nonthaburi, Thailand, or other recognized herbaria such as the Bangkok Herbarium (BK),  the Department of Agriculture, Bangkok, Thailand; the Forest Herbarium (BKF),the Department of National Parks, Wildlife and Plant Conservation, Bangkok, Thailand; the Herbarium of Queen Sirikit Botanic Garden (QSBG), Chiang Mai, Thailand.  If not provided, the herbarium specimens could be compared to the existing named specimens at the above-mentioned herbaria. 

¹Rules for Transcribing Foreign Words to Thai Script: English, French, German, Italian, Spanish, Russian, Japanese, Arabic, Malay (The Royal Ins titute ed.), Bangkok: the Royal Ins titute, 1992.

          For some plants non-native and not commercially cultivated in Thailand so that their herbarium specimens are not available at the above-mentioned herbaria, citation of the herbarium specimen numbers will be indicated under the Additional information of such monographs. If not indicated, it is suggested to inves tigate from other internationally- recognized herbaria

          The crude drug numbers (DMSc) are also cited.  The reference crude drug specimens are authenticated by the Medicinal Plant Research Institute, the Department of Medical Sciences, Nonthaburi, Thailand.

Freshly and Recently Prepared 

          The direction that a preparation must be freshly prepared indicates that it must be made not more than 24 hours before it is issued for use.  The direction that a preparation should be recently prepared indicates that deterioration is likely if the preparation is stored for longer than about 4 weeks at 15º to 25º.

Description

          In addition to macroscopical and microscopical descriptions of crude drugs, the morphological and anatomical descriptions of plants are provided for the botanical identification of the samples.  Colour photographs of the plants and crude drugs are also given. 

          Macroscopical descriptions in the monographs refer to features which can be seen by the unaided eyes or with the aid of a hand lens.  Statements of the characteris tic microscopical description of the whole drug are included in the monograph as a means for determining identity, quality, or purity.  Mos t of the transverse sections of the plants are line drawn but some are photomicrographed and inserted to illus trate the authenticity of the cellular  structures.

Identification

          Thin-layer chromatography is used as one of the principal means of identification of herbal drugs.  In some cases where isolated cons tituents of herbal drugs are available, chromatographically separated constituents are related to the known constituents used as markers¹.  For purposes of evaluation, an hR_f value is used in place of an R_f value in order to preclude the use of decimal fractions. The hR_f value is the R_f value multiplied by the factor 100, resulting in values of 0 to 100.

          In the monograph, the hR_f values of known and unknown constituents are listed in the table, accompanied by the corresponding thin-layer chromatograms.  The illustrations of thin-layer chromatograms are provided in colour photographs. 

¹Constituent(s) of a herbal material which is/are chemically defined and of interes t for quality control purposes.

          In cases where isolated constituents of herbal drugs are not readily available,  a fingerprint of the separated constituents is obtained and the positions of major spots or bands in the chromatogram are described in relation to a non-cons tituent marker, in terms of their relative R_f values (RR_f).  RR_f can be determined by the formula: 

RR_f   =  a/b 

where                a    =    R_f value of a constituent of interest, and

                          b    =    R_f value of a non-constituent marker. 

          Due to variations in the levels of constituents in different samples of herbal drug, minor deviations from one chromatogram to another can be observed.  A judgement by the analyst is needed as to the extent of deviation allowed before samples are considered incorrect or contaminated with foreign matter.  Further inves tigations should be carried out in case of doubt.

Quantitative Determination

          Unless otherwise specified, all quantitative determinations prescribed in the monographs are carried out on materials which have not been specially dried and calculations are made accordingly.

Arsenic and Heavy Metals 

          With regard to vegetable drugs, the toxic elements which may be present in sufficient quantity to pose potential risk vary from plant to plant.  The amount of these elements depends on the location, the quality of the soil, or environmental pollution.  Because of  their toxic natures, arsenic and heavy metals are of major concern.  Although not specifically required in the monograph, it is sugges ted that the maximum amounts of the toxic  elements, based on the acceptable daily intake (ADI) values, in final dosage forms of plant materials be as follows: 

       Unless otherwise indicated, the test procedures are provided in the “Limit Tests for Heavy Metals in Herbal Drugs and Herbal Drug Preparations” (Appendix 5.2).

Microbial Contamination

          Although not specifically required in the monographs, possible microbial  contamination should be controlled to such an extent that the preparations derived from them meet the requirements as described in the “Limits for Microbial  Contamination” (Appendix 10.5).

Strength(s) Available ​

          Strength(s) available is provided only as a guide and is not necessarily comprehensive.  For Solid dosage forms such as Capsules, the strength is usually given as the amount of herbal drugs, in powder form, in each unit. For herbal drugs intended for oral aqueous preparations such as Herbal Teas, the strength is usually given as the amount of herbal drugs, in powder form, in each unit dose.

Contra-indication 

          This section specifies those conditions in which the drug should NOT be used.

Warning and Precaution ​

          Under the heading “Warning”, the possible risks of certain hazards from the use of  a herbal drug are to be observed and taken care of before prescribing or adminis tering it to a patient.  Caution and careful consideration on the risk-benefit ratio of the drug should therefore be contemplated on an individual basis prior to the decision to use it. 

          On the other hand, important notes to be observed and carefully followed during and after the administration of a drug are described under the heading “Precaution”.

          Where there is a clear risk, the important warnings and precautions are selected and included under the headings “Warning” and “Precaution” in some monographs.  However, it should not be assumed that the omission of a warning or a precaution in any particular monograph means that warning or precaution may not be of clinical significance for a specific patient.

Additional Information ​

          Any personal observation of a particular drug and other special relevant information concerned are to be categorized under the heading “Additional information”.  It is not regarded as analytical requirements.

Category and Dose​

          The statements given under “Category” are provided only for information on the drug’s main pharmacological actions, which are presumably based on its use in  traditional medicine.  It should not be assumed that the substance has no other actions or uses.  Information on doses is also related to its traditional use and is intended only for general guidance.  The dose of a drug specified in this Pharmacopoeia is the usual dose for adults; some adjus tments may be necessary for individual patients, including children, depending on their conditions.  Unless otherwise s tated, the information is given for internal use.

Remark  It is to be noted that the actions and doses stated in the Pharmacopoeia do not imply any regulatory acceptance for the purpose of licensing.

Packaging and Storage

          The substances and preparations described in the Pharmacopoeia are stored in such  a way as to prevent contamination and, as far as possible, deterioration. Precautions that should be taken in relation to the effects of the atmosphere, moisture, heat, and light are indicated, where appropriate, in the monographs.

          CONTAINERS

          The container is the device that holds the substance, either in the form of the raw  material or of the finished dosage form.  The closure of the container, including the stopper, the cap, the attached dropper, etc., is considered as a part of the container. 

          The immediate container is the one which is in direct contact with the substance.   

          The container should be cleaned before use, and no extraneous matter should be  introduced into it or into the substance placed in it.  It must, likewise, not interact physically or chemically with the substance which it holds so as to alter the latter’s quality, purity, or therapeutic potency to a level below its Pharmacopoeial requirements. 

Well-closed container 

          A well-closed container must protect the contents from extraneous matter or from loss of the substance under ordinary or customary conditions of handling, shipment, storage, or sale. 

Tightly closed container 

          A tightly closed container must protect the contents from contamination  by extraneous matter or moisture, from loss of the substance, and from efflorescence,  deliquescence, or evaporation under the ordinary or customary conditions of handling, shipment, storage, or sale, and shall be capable of tight reclosure.  Where a tightly closed container is specified, it may be replaced by a hermetically closed container for a single-dose of the substance.

          STORAGE

          The following expressions are used in monographs under Packaging and storage with the meaning shown.

          Protected from light means that the product is to be stored either in a light-resistant container or in a container enclosed in an outer cover that provides such protection or stored in a place from which all such light is excluded.

          Protected from moisture means that the product is to be stored in a tightly closed container.  Care is to be taken when the container is opened in a damp atmosphere.  A low moisture content may be maintained, if necessary, by the use of a desiccant in the container provided that direct contact with the product is avoided.

          STORAGE TEMPERATURES 

          When special conditions of storage are necessary, including limits of temperature,  they are prescribed in the monograph.  Where, in a monograph, the storage conditions are mentioned using the general expressions “at room temperature”, “in a cold place”, and the like, these terms are generally defined as follows.

          Very cold temperature  Any temperature above ‒10º but not higher than 8º.  A refrigerator is a very cold place in which the temperature is maintained thermostatically between 2º and 8º.

          Cool temperature  Any temperature above 16º but not higher than 23º.

          Room temperature  Any temperature above 23º but not higher than 35º.