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Year : 2019  |  Volume : 12  |  Issue : 2  |  Page : 152-154  

An unusual color change in tetracycline HCl powder – from drug to poison

Department of Biochemistry, Faculty of Natural Sciences, Chukwuemeka Odumegwu Ojukwu University, Anambra State, Nigeria

Date of Web Publication25-Mar-2019

Correspondence Address:
Chukwuebuka Egbuna
Department of Biochemistry, Faculty of Natural Sciences, Chukwuemeka Odumegwu Ojukwu University, Anambra State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjdrdypu.mjdrdypu_97_18

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How to cite this article:
Egbuna C. An unusual color change in tetracycline HCl powder – from drug to poison. Med J DY Patil Vidyapeeth 2019;12:152-4

How to cite this URL:
Egbuna C. An unusual color change in tetracycline HCl powder – from drug to poison. Med J DY Patil Vidyapeeth [serial online] 2019 [cited 2019 Jun 16];12:152-4. Available from: http://www.mjdrdypv.org/text.asp?2019/12/2/152/254787

  Summary Top

This report is a wake-up call for the dangers associated with breach in good manufacturing practice (GMP) during the production of tetracycline HCl capsules. Tetracycline HCl (a yellow, odorless, hygroscopic, crystalline, powder) is a broad-spectrum antibiotic used for the treatment of wide range of diseases that is caused by Gram-positive or Gram-negative bacteria, atypical organisms, mycoplasmas, and rickettsiae and some other eukaryotic protozoan parasites. This drug overtime has found extensive use in clinical, veterinary, and agricultural applications. Usually, tetracycline HCl powder are encapsulated and sold by pharmaceutical companies. This sometimes follows an unusual color change from yellow to dark grayish color just within 3–6 months of production which usually go unnoticed by the unsuspecting consumers. The color change is a sign of degradation in which a toxic derivative forms (4-epianhydrotetracycline). A preliminary studies conducted over a period of 3–4 months revealed that the color changes arise from the poor handling of the environmental condition during production process which is a breach of GMP.

  Introduction Top

Good manufacturing practice (GMP) is a set of practice which ensures that the right procedures in the manufacture of pharmaceutical products are followed. GMP aims at ensuring that the desired quality in maintained. Sometimes, a breach in GMP cannot be detected nor corrected through the testing of the finished product which leads to final products of undesirable quality. Such products become a nuisance to the society causing health problems, market recalls, and huge loss on the part of the manufacturer. To minimize risks, GMP needs to be adhered to.

The focal point of analysis in this paper is the in-house industrial manufacture of tetracycline HCl, a broad-spectrum antibiotic used for the treatment of wide range of diseases caused by Gram-positive and Gram-negative bacteria, atypical organisms (such as chlamydiae), mycoplasmas, and rickettsiae and some eukaryotic protozoan parasites.[1],[2] Tetracycline HCl inhibits protein synthesis by binding specifically to 30S ribosomes and preventing access of aminoacyl tRNA to the acceptor site on the mRNA–ribosome complex. Tetracycline is also useful in disease prevention and control.[3]

Tetracycline HCl powder comprises oxygenated hydronapthacene structure [Figure 1], produced by certain strains of Streptomyces aureofaciens or by other means such as fermentation by semisynthesis.[2],[4] The first tetracycline antibiotic chlortetracycline was discovered in 1948, from the culture broth of a novel species of Streptomyces and since ever has found extensive use in clinical, veterinary, and agricultural applications – 5000 metric tons.[2] Its oxygenated hydronapthacene structure is prone to certain reactions occasioned by environmental factors or poor manufacturing practices which leads to a physical change of its yellow color to dark or brownish color over time.
Figure 1: Tetracycline structure

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  Properties of Tetracycline Hci Top

As specified in the complete drug reference guide, Martindale:[5] USP 31 (Tetracycline Hydrochloride). Tetracycline HCl is “a yellow, odourless, hygroscopic, crystalline, powder. Tetracycline hydrochloride darkens in moist air when exposed to strong sunlight. Soluble 1 in 10 of water and 1 in 100 of alcohol; practically insoluble in chloroform and in ether; soluble in solutions of alkali hydroxides and carbonates, although it is rapidly destroyed by alkali hydroxide solutions. A 1% solution in water has a pH of 1.8–2.8. The potency of tetracycline hydrochloride is reduced in solutions having a pH below 2. Store in airtight containers. Protect from light.”

  The Unstable Nature of Tetracycline Top

The wide usage and the very sensitive nature of tetracycline HCl calls for caution. From my experience and preliminary assessment of the storage and production conditions of tetracycline HCl in the quality control department of the pharmaceutical company, it is glaring that the poor handling of tetracycline HCl capsule powder often results in changes of the physicochemical properties which is seen by sudden change of the yellow color powder in the capsule to dark grayish color just after 3–4 months of production. This results from negligence or lack of total compliance of GMP practices from raw material handling, filling of capsules, blistering, packaging, and to storage owing to the improper exposure of tetracycline HCl, especially in warm, moist, and acidic environments. With this in mind, even after full compliance, stability test for tetracycline HCl and its degradation product needs to be examined periodically with time. This observations and recommendations came to a satisfactory conclusion based on the results obtained from tetracycline HCl samples subjected to different storage conditions (in airtight container, in airtight container + cold temperature, in airtight container + hot temperature, and tetracycline HCl in moist exposed container which was kept for a duration of 3–6 months.

  Degradation Products and Its Associated Toxicity Top

The most important of the degradation product of tetracycline is 4-epianhydrotetracycline HCl [Figure 2], a tetracycline impurity D formed from secondary degradation product by epimerization reaction of tetracycline and dehydration at the C6 position to aromatize the B ring.[6],[7] The degradation process can be illustrated in two ways. First, it reversibly epimerizes to 4-epitetracycline which dehydrates irreversibly to 4-epianhydrotetracycline and then reversibly to anhydrotetracycline or that tetracycline irreversibly dehydrates directly to anhydrotetracycline, which reversibly epimerizes to 4-epianhydrotetracycline.
Figure 2: 4-Epianhydrotetracycline structure

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Although 4-epianhydrotetracycline now serves as an important standard for monitoring tetracycline stability, the degradation is associated with a loss of antibiotic activity and enhanced toxicity. The 4-epianhydrotetracycline is considered biologically active and is implicated in tetracycline toxicity.[6] Studies using rats has shown that 4-epianhydrotetracycline causes renal toxicity and a decrease in mitochondrial respiration.[7] Another study shows that 4-epianhydrotetracycline HCl can have a 250-fold higher toxicity depending on the system under study.

  Way Forward Top

A study by Sigma-Aldrich[8] shows that tetracycline stored for approximately 4 years below 0°C still displayed a single spot by thin-layer chromatography. This shows that tetracycline HCl is stable at low temperature. Pharmaceutical companies, especially those in the tropical regions, should ensure that raw materials and the finished products are kept at low temperature while ensuring dehumidified condition, light, and acidic/alkaline conditions protection during filling of the capsules and other production processes. On the part of the end users, it is recommended that tetracycline drugs should be purchased from trusted sources and that a preliminary check of the color of tetracycline HCl should be done before consumption/administration. Finally, the quality control unit of a pharmaceutical company should optimize assay methods using primary tetracycline HCl and the degradation product standards for easy detection as against the usual ultraviolet spectrophotometric methods

  References Top

Chopra I, Roberts M. Tetracycline antibiotics: Mode of action, applications, molecular biology, and epidemiology of bacterial resistance. Microbiol Mol Biol Rev 2001;65:232-60.  Back to cited text no. 1
Arun NR. Tetracyclines. Group Seminar Kalesse and Gaich. Leibniz University Hannover; 2012. Available from: https://www.kalesse.uni-hannover.de/fileadmin/ak-kalesse/pdf/Arun_Naini-_Tetracyclines_22.10.12.pdf. [Last retrieved on 2018 May 21].  Back to cited text no. 2
Pena A, Carmona A, Barbosa A, Lino C, Silveira I, Castillo B, et al. Determination of tetracycline and its major degradation products by liquid chromatography with fluorescence detection. J Pharm Biomed Anal 1998;18:839-45.  Back to cited text no. 3
British pharmacopeae. Tetracycline HCl. Electronic, Version 17. TSO (The Stationery Office): UK. 2013.  Back to cited text no. 4
Sweetman SC, editor. Tetracycline HCl. Martindale, the complete drug reference Guide. 36th ed. Pharmaceutical Press: London SEl 7JN, UK. 2009. p. 362.  Back to cited text no. 5
ChemicalBook 4-Epi-Anhydrotetracycline Hydrochloride. Available from: http://www.chemicalbook.com/ChemicalProduct Property_DE_CB9171671.htm. [Last retrieved on 2017 Aug 21].  Back to cited text no. 6
Toku-E. Epianhydrotetracycline HCl, EvoPure®. Available from: https://www.toku-e.com/4-epianhydrotetracycline-HCl-EvoPuresupregsup-P661.aspx. [Last retrieved on 2018 May 21].  Back to cited text no. 7
Sigma-Aldrich. Tetracycline Hydrochloride. Product Number T 3383. Available: Available from: http://www.sigmaaldrich.com/catalog/product/sial/t3383?lang=en and region=NG. [Last retrieved on 2018 May 21].  Back to cited text no. 8


  [Figure 1], [Figure 2]


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