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38 Cards in this Set
- Front
- Back
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Mycobacteria - describe the genus
What is "myco-"? |
Aerobic, gram +ve, rods - However, they do not stain under the graim stain, due to their waxy cell walls. (The "myco-" is latin for both fungus and wax; here it relates to the wax). They are "acid-fasr" staining, and "atypical".
The cell wall increases the hardiness of the genus. |
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Mycobacteria - members of genus?
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M. tuberculosis (TB)
M. avium complex (spp) M. bovis (can cause TB) M. leprae (leprosy) M. ulcerans ("Bruruli" or "Bairnsdale" ulcer) |
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Mycobacterium ulcerans
- how do you get it - how does it hurt - how do you treat it? |
Endemic (region specific); transmitted from environment rather than individuals; most likely aquatic; mechanism of transmission unknown
Toxin: mycolactone necrotic to fat and muscle Surgical debridement of necrotic tissue is the mainstay of treatment. Treatment with rifampicin and amikacin for 8 weeks may reduce the extent of debridement required. |
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MAC
- what types of infections? |
Pulmonary
- bronchiectasis - alveolar: more likely where there is lung disease Disseminated MAC - in the immunocompromised |
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How do you treat MAC?
- pulmonary |
At least 3 drugs needed (TG)
Daily regimen 1. Ethambutol 15mg/kg 2. Clarithromycin 500mg bd or Azithromycin 500mg d 3. Rifampicin 600mg d or Rifabutin 300mg d **If there is macrolide resistence or extensive disease et.al., may consider addition of IM amikacin or streptomycin three times weekly for first 2/12 NB there is also a 3 times weekly oral regimen Continue for 12 months AFTER sputum cultures become clear |
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How do you treat MAC?
- disseminated |
As for pumonary, except remember to adjust HIV regimens with the rifamycin.
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How do you prevent MAC?
- in what patient group? - primary prevention? - seconday prevention? |
- HIV patients with CD4 count <50/microlitre (exclude disease first). Stop if CD4 count rises above 100
- Use clarithromycin/azithromycin OR rifabutin - Secondary prevention in HIV patients: USE FOR LIFE unless CD4 rises above 100. - Use clarithromycin/azithromycin plus ethambutol and sometimes RIFABUTIN |
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TB
- principles of treatment (4) |
1. specialist management
2. notifiable disease with contact tracing mandatory 3. microbiological confirmation and resistance testing essential 4. patient compliance essential: comprehensive education, DOT (directly observed therapy), close follow-up |
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TB
- baseline testing required - what else before treatment |
- weight
- LFTs - RFTs - Vision test (color and acuity, ethambutol) - FBE - HIV (with counselling) - contraceptive advice for females |
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TB
- what is the "standard short course therapy" |
1. Rifampicin, 6/12, 600mg d (450mg if <50kg)
2. Isoniazid, 6/12, 300mg d 3. Ethambutol, 2/12, 15mg/kg 4. Pyrazinamide, 2/12, 25mg/kg up to 2g Daily regimen 3-weekly regimen is only recommended with DOT |
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TB
- when is the short course a no go? |
1. when there is resistence
2. when there is extensive disease (and some types of extra-pulmonary) 3. when there is a CI |
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TB
- what needs to be given with isoniazid and why? |
25mg pyridoxine, to prevent peripheral neuropathy
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TB
- why are 2 drugs used only for 2 months? |
They are to be used while susceptability tests are conducted. Ethambutol can be discontinued earlier if susceptability results are early and show susceptability to rifampicin and isoniazid. Pyrazinamide cannot be stopped early.
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TB
- ongoing monitoring |
1. ADHERENCE
2. Visual (ask at each visit, and test 3 monthly) 3. LFTs |
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TB
- what if the patient is pregnant - what if the patient is a child |
- it is even more imperative to treat; all drugs can be used in pregnancy, although US guidelines say there is not enough evidence for pyrazinamide (other authorities disagree)
- generally children are not infectious and do not need to be excluded from school; give standard short course, except do not give ethambutol if under 6 because won't be able to report visual symptoms (obviously lower the dose) |
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TB
- and HIV? - and resistance? |
- HARD, rifabutin is a less potent CYP3A4 inhibitor
- 7-10% have resistence to isoniazid, 1% have resistence to isoniazid and rifampicin; resistence more common overseas - Treat for longer than 6/12; other drugs include streptomycin, amikacin,fluroquinolones |
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TB
- when do you treat "latent TB" |
Positive tuberculin skin test without any size of active disease and no TB vaccination history and
- HIV, immunosuppressed - Chronic diseases - contacts with TB Treat with isoniazid 300mg d for 3-6/12 and pyridoxime 25mg d |
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Isoniazid
- MOA - Indications (2) - CIs (2) - Cautions (3 easy ones) - BF / Preg |
- May inhibit mycolic acid synthesis (part of cell wall) which is bacteriostatic if resting or bacteriocidal if dividing
- TB, Latent TB - Previous severe ADE, acute liver disease - Greater risk of peripheral neuropathy with malnutrition, diabetes, HIV, alcoholism, renal impairment - Greater risk of hepatotoxicity with alcoholism, age >35, liver disease, women - May cause seizures & also interacts with CBZ and Phenytoin (epilepsy) |
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Isoniazid
- DIs |
- Increased seizure risk
- Increase BGLs - Increase metabolism of CBZ and Phenytoin |
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Isoniazid
- PBS - Dose form - Dose |
YES
100mg.100 tab (Isoniazid) Latent TB: 300mg d TB: 300mg d |
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Isoniazid
- Adverse effects |
Common:
- peripheral neuritis (if not given with pyridoxine) - hepatitis - antinulclear antibodies w/o SLE - acne, tierdness, rash, fever Infrequent: optic neuritis, seizures, memory impairment, encephalopathy, psychosis |
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Isoniazid counselling
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1. Take on an empty stomach (1hr<food>2hr) WITH PYRIDOXINE 25mg
2. Stop treatment and tell doctor if you get jaundice (persistent n/v, unusual tierdness, jaundice); or visual changes; or fever/rash Drug should be stopped if hypersensitivity occurs |
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Isoniazid monitoring
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- LFTs
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Ethambutol
- MOA - Indications - CI - Considerstaions - Preg / BF |
- May inhibit mycolic acid incorporation into cell wall; slowly bacteriostatic
- TB, MAC, MAC secondary prevention - Optic neuritis - May cause further visual deterioration if there are existing defects, e.g. diabetes, cataracts - Inability to report visual changes (children <6) - RI increased risk of visual problems - Cat A, safe in breastfeeding |
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Ethambutol
- A/Es |
Common
JUST OPTIC NEURITIS - color blindness, decreased visual acuity, usually reversible; unlikely when course is <2/12, no RI, <15mg/kg d Rare: acute gout, more likely if already has gout |
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Ethambutol
- Dose forms - PBS - Dosing |
- not on PBS
- 15mg/kg/d up to 1.6g (up to 20mg/kg in first 2/12 of TB treatment) - RI: severe: dose every 48 hr - RI: mod: dose every 36 hr |
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Ethambutol
- Counselling |
VISION
- less clear - color perception Stop and report |
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Ethambutol
- monitorin |
Visual function:
baseline monthly (AMH) or 3 monthly (TG) |
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Pyrazinamide
- MOA - Indications - CI - Cautions - Preg, BF |
- Bactericidal against M. tuberculosis, and inactive against other strains of mycobacterium!
- Indicated for TB only - CI in severe liver disease and acute gout - Cautions: inhibits urate excreation; can worsen gout and may cause urate crystals and worsening renal function if there is mod-severe RI - Safe in pregnancy, B2, and contact an info centre about BF |
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Pyrazinamide
- A/Es |
Common
- hyperuricaemia - sore joints - nausea Infrequently: liver toxicity: rare with doses <25mg/kg, and varies from asymptomatic to massive hepatic necrosis! |
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Pyrazinamide
- dose - dose forms - PBS |
- 20-25mg/kg up to 2g d
- not on PBS, not marketed in AUS, go through SAS - no info on dose forms in AMH |
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Pyrazinamide
- counselling points - monitoring |
- Stop and tell doctor if there are symptoms of jaundice (continuous n/v, unusual fatigue, yellowing of skin or whites of eyes, dark urine, pale faeces)
- baseline FBE, uric acid, CrCl, U+E, LFTs - Monitor LFTs only if risk factors present - Stop if symptomatic hyperuricaemia occurs (nephtolithiasis or gout) |
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Why aren't pyrazinamide and rifampicin together recommended for latent TB?
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Risk of hepatic injury is high; acceptable risk for treatment of TB. (There is also a risk with Isoniazid but not of massive hepatic necrosis)
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Ethambutol
- dose forms |
100mg.100 tab, 400mg.100 tab (Myambutol)
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Ethambutol and pyrazinamide drug interactions
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ZERO
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What is BCG
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Bacillus Calmette-Guerin
Live attenuated M.bovis, which produces an inflammatory reaction, reducing or eliminating superficial bladder tumors |
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BCG
- CI - administration advice - urination after treatment? |
- CI in immunosuppression and active TB infection; gross hematuria and for 2 weeks after bladder surgery; stop treatment if there is a UTI
- Instil into bladder; retain for at least 2 hours; patient should turn every 15min, to ensure bladder contact. Also patient should not drink any fluids during and 4hr before treatment - aim to prevent spread of infection: urinate by sitting on toilet and disinfect toilet seat |
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BCG
- Adverse effects - Dose schedule - Brands - PBS |
- dysuria, frequency, urgency
- low grade fever and flu-like symptoms for 1-2 days (if persistent, postpone treatment and consider treatment for tuberculosis) - Normal course: 1 vial weekly for 6-12 weeks, and then sometimes monthly for up to 3 years - OncyoTICE, ImmuCyst, PBS-R |
