Drug Panorama Issue No.1, 

 In this Issue

 
Editorial :-Antibiotic Resistance raises its ugly head
  Section One
  Treating TB Patients : A Primer
  The overall objective of TB Control
  The importance of defining Sputum Smear results in Pulmonary cases
  Main Properties of Anti-TB Drugs
  Alternative Tuberculosis Treatment Regimens
  When to take sputum smear examination ?
Section Two
Adverse Drug Reactions Scan
Section Three
  Drug Policy Issues : Drug Advertising and Promotion
 
 

 

Antibiotic Resistance Raises its Ugly Head

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Urgent action is needed to combat the spread of antibiotic resistant bacterial diseases in many parts of the world. Antibiotics and other antimicrobial agents are losing their effectiveness. Once a new drug has become widely used, resistance to it is already emerging somewhere in the world. In the past, the pharmaceutical industry was able to provide a new class of antibiotics- cephalosporins and quinolones-which could successfully deal with all bacteria, now, however resistance to both is appearing everywhere when no new antibiotics are anticipated. At the same time micro-organisms, including pneumococci, staphylococci, enterococci and strains of tuberculosis bacilli are spreading with unexpected rapidity having developed defence mechanisms against existing antibiotics.

Tuberculosis, cholera and other diaorrheal diseases, which together kill millions of people, are already resistant to many types of antibiotics. There has been such a dramatic increase in drug resistance in diaorrheal diseases in many parts of the developing world that shigella organisms are resistant to almost all affordable and available anti-microbial drugs. Resistance is a much greater problem in the developing world where the sale of antimicrobials is largely unrestricted. Misuse of antibiotics is mainly to blame for this crisis. When antibiotics become universally available they tend to be used in excess and inappropriately. Lack of reliable scientific information is also a contributing factor in developing countries. The consequences of anti-microbial resistance are seen in increased morbidity and mortality due to bacterial diseases.

Faced with resistant infections, clinicians are forced to resort to second line of treatment which invariably involves more expensive drugs and prolonged hospital stay. Anti-microbial resistance is costly for both patients and health services. However a great deal can be done at very little cost to contain the spread of resistant bacteria by improving the flow of existing information and revising medical practices.

 

Treating TB Patients : A Primer

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About one-third of the world's population is infected by mycobacterium tuberculosis, which kills more people than any other infectious agent. 98% of tuberculosis deaths occur in developing countries, the main reason for increasing global tuberculosis burden are pinned down to poverty, widening rich-poor gap, inadequate case detection, diagnosis and cure, increasing world population, changing age structure and impact of the HIV pandemic. Efforts to control tuberculosis globally have failed so far because of inadequate case management and over reliance on BCG besides inadequacy of political commitment and health services.

Tuberculosis treatment has an initial phase and a continuation phase. In case of new patients (a patient who has never taken anti tuberculosis drugs for more than one month) initial phase (2 months), Directly Observed Treatment Short Course (DOTS) is essential to ensure that the patient takes every single dose. This protects rifampicin against development of drug resistance. The risk of drug resistance is higher during the initial phases of treatment when there are more tuberculosis bacilli. In the continuation phase of 4-6 months, fewer drugs are necessary but for a longer period. DOTS is ideal when the patient receives rifampicin in continuation phase. Weekly supervision is the next best if local conditions do not allow DOTS. The risk of drug resistance is less during continuation phase when there are fewer tuberculosis bacilli.

 

The overall objective of TB Control

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The overall objective of tuberculosis control is to reduce morbidity, mortality and to prevent the development of drug resistance. Standardized short course chemotherapy under direct observation at least during the initial phase of treatment and in all identified smear positive tuberculosis cases is the strategy. The target for tuberculosis control is to achieve a cure rate of 85% of the detected new cases of sputum smear positive tuberculosis which will result in immediate decrease in tuberculosis prevalence and rate of transmission followed by a gradual decrease in the incidence of tuberculosis and reduced acquired drug resistance. This makes future treatment of tuberculosis easier and more affordable.

All National Tuberculosis Control Programmes also target to detect seventy percent of sputum smear positive tuberculosis.

 

 

The importance of defining Sputum Smear results in Pulmonary cases

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The importance of defining sputum smear results in pulmonary cases is in the identification of smear positive cases as they are most infectious and have increased mortality. A patient with at least two sputum specimens positive for Acid Fast Bacilli (AFB) or a patient with at least one sputum positive for AFB and radiographic abnormality consistent with pulmonary tuberculosis (PTS) or a patient with one sputum specimen positive which is culture positive for mycobacterium tuberculosis is considered to be suffering from smear positive TB. A patient who fulfils the following criteria i.e. two sets of at least two specimens taken at least two weeks apart negative for AFB on microscopy or radiographic abnormality consistent with pulmonary tuberculosis and a lack of clinical response despite one week of broad spectrum antibiotics therapy is considered smear negative. PTB Patients who are severely ill with two sputum smear negative and radiographic abnormalities consistent with extensive PTB (interstitial or miliary) are also classified as smear negative. The decision of the physician to treat with full curative course of anti TB therapy is of paramount importance.

 

 

Main Properties of Anti-TB Drugs

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There are three main properties of anti tuberculosis drugs: bactericidal ability, sterilising ability and ability to prevent resistance. Anti- tuberculosis drugs possess these properties to different extents. Isoniazid and rifampicin are the most powerful bactericidal drugs active against all populations of tuberculosis bacilli. Pyrazinamide and streptomycin are also bactericidal against certain populations. Flyrazinamide is active in an acid environment and inside macrophages. Streptomycin is active against rapidly multiplying extra-cellular tuberculosis bacilli, Ethambutol and thiacetazone are bacteriostatic and are used in association with more powerful bactericidal drugs to prevent emergence of resistance.

 

 

Properties and Recommended Dosage of Anti-TB Drugs

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    Essential Anti-TB Drug
    (Abbreviation)		      Mode of Action

Daily

 Recommended Dose (Mg/Kg) Intermittent

3 x/Wk

2 x/Wk

      lsoniazid (H)       Bactericidal 5 (4-6) 10 (8-12) 15 (13-17)
     Rifamplein (R)       Bactericidal 10 (8-12) 10 (8-12) 10 (8-12)
     Pvrazinamide (Z)       Bactericidal 25 (20-30) 35 (30-40) 50 (40-60)
     Streptomycin (S)       Bactericidal 15 (12-18) 15 (12-18) 15 (12-18)
     Ethambutol (E)       Bacteriostatic 15 (15-20) 30 (25-35) 45 (40-50)
    Thioacetazone (T)       Bacteriostatic 2.5

NOT APPLICABLE

 

 

Alternative TB Treatment Regimens                                                                                                          go top
TB Treatment Category Tuberculosis  Patients Alternative TB Treatment Regimens
  Initial Phase Continuation Phase
Category One New Smear Positive and   2 S H R Z ( E H R Z )  6 H E
  seriously ill extra pulmonary  2 S H R Z  ( E H R Z)  4 H R
  or smear negative pulmonary  2  S H R Z ( E H R Z )  4 H3R3
  (severe Tuberculosis)

 2  E3 H3 R3 Z3

  4 H3R3
       
Category Two   Sputum smear positive :  2 SHRZ / 1 H R Z E

 5 H3 R3 E3

    Relapse  2 SHRZ / 1 H R Z E

 5 H R E

    Treatment failure  2 S3 H3 R3 Z3 E3 /

 5 H3 R3 E3

  Return after default  1 H3 R3 Z3 E3  
       
Category Three   Smear Negative PTB and
  Extrapulmonary TB (less severe)		  2 H R Z or 2 H3 R3 Z3

 6 H E

 2 H R Z or 2 H3 R3 Z3

 2 H R / 4 H

 2 H R Z or 2 H3 R3 Z3

 2 H3 R3 / 4 H

 2 H3 R3 Z3

  4 H3 R3
       
Category  Four Chronic case (still sputum after supervised re-treatment) NOT APPLICABLE
(Refer to special center if second line drugs available)
     
 RELAPSE A tuberculosis patient who previously received drug treatment and was declared cured and has once again  developed sputum smear positive tuberculosis.
 TREATMENT FAILURE A new tuberculosis patient who is still sputum smear positive five months or more after treatment
 RETURN AFTER DEFAULT A new tuberculosis patient who has completed at least one month of tuberculosis treatment and has returned after at least two month interruption of treatment.

Patients with sputum smear positive tuberculosis should be monitored by sputum smear examination.
Chest radiography is wasteful as a monitoring procedure. 
Clinical monitoring is the usual way of measuring response to treatment in sputum smear negative tuberculosis cases.

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