Presentation on theme: "Chemotherapy of Tuberculosis. Tuberculosis Chronic granulomatous disease. Usually affects the lungs, up to one third of cases, other organs are involved."— Presentation transcript:
Chemotherapy of Tuberculosis
Tuberculosis Chronic granulomatous disease. Usually affects the lungs, up to one third of cases, other organs are involved.
Mycobacterium tuberculosis complex: Mycobacterium Mycobacterium tuberculosis : Mycobacterium Rod shaped, non- pore-forming, thin aerobic bacterium. Important agent for human disease. M. bovis Important cause of tuberculosis for transmitted by unpasteurised milk. M. africanum West, central & east africa. M.microti Less virulent, rarely encountered organism.
M.tuberculosis transmitted from patient with infectious pulmonary Tb to other persons By droplet nuclei, Aerosolised by coughing, sneezing or speaking. As many as 3000 infectious nuclei per cough.
Tiny droplets dry rapidly. Smallest droplets (<10 um in diameter) Suspended in the air for several hours, May gain direct access to the terminal air passages when inhaled.
Risk factors for acquiring infection with M.Tuberculosis: Probability of contact with the case of Tb. Intimacy and duration of that contact. Degree of infectiousness of the case. Shared environment of the contact.
Risk factor for developing disease after being infected : Individuals innate susceptibility to disease. Level of function of cell mediated immunity.
Primary Tuberculosis Results from initial infection with tubercle bacilli. Children up to 4 yrs of age. Middle, lower lung zone affected mainly. Rapid progression to illness in HIV patients.
Pleural effusion: due to penetration of bacilli into pleural space from subsequent subpleural area. Lymphadenopathy: due to spread of bacilli from lung parenchyma through lymphatic vessel. Obstruction & subsequent segmental collapse: as enlarged lymph node compress bronchi. Obstructive emphysema: due to partial obstruction. Granulomatous lesions: seen in severe cases as bacilli reach blood stream from pulmonary lesion/lymph nodes
Secondary Tuberculosis Adult type. Dormant bacilli, may persist for years before reactivating to produce Secondary Tuberculosis - often infectious. Localised to the apical & posterior segments of the upper lobes, where high oxygen concentration favours mycobacterial growth.
Secondary Tb..... Early symptoms: fever, night sweats, weight loss, malaise, weakness. Development of Cough : non productive initially, production of purulent sputum.
Diagnosis of Tuberculosis AFB (Acid Fast Bacilli) microscopyPresumptive diagnosis. Mycobacterial cultureDefinitive diagnosis Nucleic acid amplificationUse limited due to low sensitivity. Drug susceptibility testingTo find out drug resistance. Radiographic procedureBased on abnormal chest radiographic findings Tuberculin skin testing Lack of mycobacterial specificity limits use Cytokine release assayDiagnosis of latent tuberculosis infection.
Treatment Aim of treating Tuberculosis: To interrupt tuberculosis transmission by rendering patients non-infectious. To prevent morbidity & mortality by curing patients with tuberculosis disease.
Antitubercular drugs First line drugs : High efficacy & low toxicity. Isoniazid 5mg / kg /d, max of 300 mg / d Rifampin 10 mg/kg/d, max of 600 mg / d Pyrazinamide mg/kg/d, max of 2g / d Ethambutol mg / kg / d Streptomycin 15 mg / kg / d
Second line agents Either low efficacy or high toxicity or both Slide 76Slide 76 DrugsDoses Amikacin15 mg/kg/d Aminosalicylic acid8-12 g/d Capreomycin15 mg/kg/d Ciprofloxacin1500 mg/kg/d Clofazimine200 mg/d Cycloserine mg/d Ethionamide mg/d Levofloxacin500 mg/d Rifabutin300 mg/d Rifapentine600 mg o.d weekly
Isoniazid Bacteriostatic for resting bacilli but bactericidal for rapidly dividing micro- organisms. Minimal effective conc.: ug/ml. Peak plasma conc. : 1-2 hrs. Good oral & parenteral absorption.
Metabolism via acetylation (acetylisoniazid) & via hydrolysis (isonicotinic acid).
N-acetyltransferase type 2 (NAT 2) Fast acetylators Slow acetylators t½ of INH =1hr t½ of INH =2-5 hrs Hepatic insufficiencyIn case of renal impairment, may accumulate to toxic concentration. Dosage reduction recommended
MECHANISM OF ACTION….INH
Resistance 1.Mutation in catalase peroxidase Decreases its activity Prevent conversion of prodrug to active metabolite. 2.Mutation in inh A gene involved in mycolic acid biosynthesis. Resulting in over expression of inh A.
Tuberculous cavity contains 10 9 micro- organism. 1 in 10 6 bacilli genetically resistant to INH. So, resistant mutants selected out in INH monotherapy.
INH induced hepatotoxicity. Multilobular necrosis – by liver biopsy. Risk factor : Older age & excessive alcohol intake. <20 years: Rare years & >50 years: elevated serum transaminase level. > 5 times serum transaminase level: DISCONTINUE Drug.
Peripheral neuropathy: Due to interference with utilization of pyridoxine and its increased excretion in urine. Paresthesia of feet & hands. Pyridoxine 10 mg/d for treatment.
Neurotoxicity: Convulsion, in patients with seizure disorder. Optic neuropathy.Optic neuropathy.Optic neuropathy.Optic neuropathy. Muscle twitching, stupor.
Hematological reaction: Agranulocytosis, eosinophilia, thrombocytopenia. Sideroblastic anemiaSideroblastic anemia (presence of ring sideroblasts in the bone marrow)Sideroblastic anemia Sideroblastic anemia Reversible. INH deprives ALAS2 (delta-aminolaevulinic acid synthase 2) of pyridoxal phosphate therefore inhibits haem synthesis. Overcome by concomitant administration of pyridoxine(25 to 50 mg/d).
Hypersensitivity reaction: Fever, rashes, hepatitis, SLE. INH overdose: Tonic - clonic seizure, metabolic acidosis, coma in pregnant women.Tonic - clonic seizure, metabolic acidosis, coma in pregnant women.Tonic - clonic seizuremetabolic acidosis coma in pregnant womenTonic - clonic seizuremetabolic acidosis coma in pregnant women Pyridoxine – specific antidote.
Pyridoxine – a necessary co-factor for production of neurotransmitter GABA. In isoniazid overdose, the susceptibility to seizures is induced by isoniazid binding to endogenous pyridoxine, make it inactive and resulting in a depletion of GABA in the brain. Therefore, the administration of exogenous pyridoxine directly counteracts this neurotoxic effect.
Increase in the generation of lactic acid as a result of muscular activity and recurrent seizures. Generation of acidic INH metabolites. Increase in ketoacids due to enhanced fatty acid oxidation.
COMA due to CNS catecholamine depletion.
Management : GI decontamination with gastric lavage, Stabilization of vital signs with provision of patent airway and IV sodium bicarbonate, Cardiovascular support with IV fluids and vasopressors. IV pyridoxine – highly effective for INH intoxication and should be administered to all symptomatic patients.
Uses of INH Latent Tb Recent converters: who test positive within 2 years after a documented negative skin test. Immunocompromised patients. Prevention, in close contacts of active cases of pulmonary Tb.
INH Rifampin Effect: Hepatotoxicity. Mode: Altered INH metabolism by rifampin. Monitoring: If LFT alter, discontinue one or both agents.
Rifamycins Rifampin Rifabutin Rifapentine
Mechanism of action: Bactericidal at 3-12 ng/ml for both intracellular & extracellular microorganisms. Kills organisms at poorly accessible sites like abscess, lung cavities.
Binds to β subunit of bacterial DNA dependent RNA polymerase. Suppression of initiation of chain formation but no chain elongation in RNA synthesis. Inhibit RNA synthesis in mammalian mitochondria, viral DNA dependent RNA Polymerase, reverse transcriptase at high concentration.
Mechanism of resistance 1.Mutation between codons 507 & 533 of polymerase rpo B gene for β subunit of RNA polymerase. Prevent binding of rifampin to RNA polymerase. 2.Alterations in the target of drug: DNA dependent RNA polymerase.
Adverse effects Hepatitis from rifampin rarely occurs in patients with normal hepatic function. Chronic liver disease, alcoholism, and old age increase the risk of severe hepatitis when rifampin is given alone or concurrently with isoniazid. < 5% of patients, serum level of aminotransferase, phosphatase, bilirubin increase slightly, but diminish spontaneously despite continuation of treatment.
Rifampin may potentiate toxic effect of INH, particularly in patients in whom INH is rapidly inactivated. Rifampin induces microsomal enzyme. Facilitate conversion of monoacetylhydrazine, a metabolite of acetylated INH into an acylating agent that could cause hepatic necrosis.
Light chain proteinuria. Imparts a harmless orange colour to urine, sweat, tears, and contact lenses (soft lenses may be permanently stained)
GI disturbances – (epigastric distress, nausea, vomiting, abdominal cramps, diarrhea) occasionally required drug discontinuation. Thrombocytopenia, transient leukopenia, and anaemia have occurred during therapy.
Ethambutol Inhibit mycobacterial arabinosyl transferases, which is involved in polymerization reaction of arabinoglycan …….essential component of mycobacterial cell wall.
Adv. : Retrobulbar neuritis causing loss of visual acuity and red-green colour blindness. (Serious). Not recommended for children under 5 years of age because of concern about the ability to test their visual acuity.
Pyrazinamide PRODRUG Pyrazinoic acid pyrazinamidase (ACTIVE FORM) encoded by pnc A BACTERICIDAL Impaired mutation of pnc A RESISTANCE
Hepatotoxicity (in 1–5% of patients), nausea, vomiting, drug fever, and hyperuricemia. Hyperuricemia may provoke acute gouty arthritis.
Streptomycin Binds with S12 ribosomal protein. Interfere with initiation of peptide formation. Misreading of mRNA. Breakup of polysomes into nonfunctional monosomes. Irreversible inhibition of mycobacterial protein synthesis.
Ototoxic and nephrotoxic.(8 th cranial nerve involves). Vertigo and hearing loss -most common. may be permanent.
Ethionamide Inhibits mycobacterial growth by inhibiting the activity of the enoyl-ACP reductase of fatty acid synthase II. Thus inhibit mycolic acid biosynthesis with consequent impairment of cell-wall synthesis.
Chemoprophylaxis To prevent development of active TB in patients who are at risk. Tuberculin skin test interferon test Mantoux testT-Spot.Tb Heaf testQuantiFeron Tb Gold Tine test
Indications for chemoprophylaxis: 1.New born of a mother with active TB. 2.Young children (<6 yrs.) with positive TB. 3.Household contacts of patients with TB. 4.Patients with positive tuberculin test with additional risk factors such as diabetes mellitus, malignancy, AIDS.
Isoniazid prophylaxis, continued for 12 months. Pyridoxine co-administered. HIV infected, exposed to MDRTb – rifampin + pyrazinamide (with close monitoring for hepatic toxicity) or high-dose ethambutol +pyrazinamide, with or without a fluoroquinolone.
FOUR drug regimen treatment for whom?
1.Known to exposed to drug resistant organisms. 2.Recent immigrants. 3.Pts with extrapulmonary TB. 4.Pts with meningitis. 5.HIV pts.
Continued for atleast 6 months after three negative cultures obtained.
MDT Objectives: 1.To make patient non-infectious as early as possible by rapidly killing the dividing bacilli by using 3 to 4 bactericidal drugs. 2.To prevent the development of drug-resistant bacilli. 3.To prevent relapse by killing the persisters (dormant bacilli). 4.To reduce the total duration of effective therapy.
Recommended by WHO. Choice of treatment regimen based on: Their efficacy, effectiveness, availability of financial recourses.
Long course regimens: INH alone with one or two bacteriostatic drugs for 18 months. Poor patient compliance, high failure rate.
Short course regimen: 6-9 months duration. Highly effective. Less toxic.
Intensive phase: tuberculocidal drugs daily or thrice weekly for a period of 2-3 months. - To render the patient non-contagious. INH 300mg + Rifampicin 600 mg + Pyrazinamide 1500 mg + Ethambutol 1000 mg/Streptomycin 1000 mg + Pyridoxine 10 mg daily for 2 months.
Continuous phase: drugs usually INH & Rifampicin daily or thrice weekly for a period of 4-6 months. - Helps to eliminate persisters & prevents relapse. - INH 300mg +Pyridoxine 10 mg + Rifampicin 600 mg daily for 4 months.
DOTS …. Backbone of RNTCP
RNTCP: Revised National Tuberculosis Control Programme, launched in 1997 DOTS: Directly observed treatment short course.
Patient is administered drugs under the supervision of a health worker to ensure that drugs are actually consumed. Supervised and monitored by bacteriological examinations. Aimed at ensuring patient compliance thus preventing the emergence of drug resistant tuberculosis.
H=isoniazid, R=Rifampicin, Z=Pyrazinamide, E=Ethambutol, S=Streptomycin HRZ & E= orally ; S= i.m Prefix= number of months, Subscript= doses per week. Diagnostic category Type of patientIntensive phase Continuation phase Total duration (months) Category 3Sputum negative, not seriously ill, extrapulmonary, not seriously ill Daily 2 HRT Thrice weekly 2(HRZ) 3 4HR 4(HR) Category 4Chronic or suspected MDR-TB cases Specially designed standardized or individualized regimen
DOTS plus : - first WHO endorsed DOTS-Plus programmes began in To treat MDR-TB using second line anti TB drugs.second line - Recommended in areas where DOTS is fully in place.
Five components of DOTS Plus
Sustained political and administrative commitment A well functioning DOTS programme. Long term investment of staff and resources. Coordination efforts between community, local governments, and international agencies. Addressing the factors leading to the emergence of MDR-TB
Diagnosis of MDR-TB through quality- assured culture and drug susceptibility testing. Proper triage of patients for Culture & testing and management under DOTS-Plus. Co-ordination with National and Supra-National Reference Laboratories
Appropriate treatment strategies that utilize second-line drugs under proper management conditions Rational standardized treatment design (evidence- based) Directly observed therapy (DOT) ensuring long-term adherence. Monitoring and management of adverse drug reactions. Adequate human resources.
TB treatment in HIV patients: Rifabutin preferred over rifampicin in HIV patients on antiretroviral drugs as it doesnt interact with PIs.
Role of glucocorticoids in tuberculosis
Tuberculosis is a relative CI for use of glucocorticoids.
TB of serum membrane like pleura, peritonium, pericardium, meninges, to prevent fibrous tissue formation. To treat hypersensitivity reactions to antiTB drugs. Tuberculosis of eye, larynx, genitourinary tract to prevent fibrosis & scar tissue formation. Once patients general condition improves, steroid is tapered to avoid HPA axis suppression.