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FARMAKOLOGI OBAT
ANTIBIOTIK
Rina Wijayanti, M. Sc., Apt
Ideal Antimicrobial Agent
Soluble in body
Stable in body
Selectively toxic
Consistent Toxicity
Non-allergic
Bacterial resistance difficult to develop
Long shelf life
Reasonable cost
Terms/Concepts of Antimicrobial Agent
• Selective Toxicity
• Spectrum of Activity
• Mode of Action
• Side Effects
• Resistance
Selective Toxicity
• Concentration that eliminates pathogen
– Therapeutic dosage level
• Concentration that causes damage to host
– Toxic dosage level
• Chemotherapeutic index =
Maximum tolerable dose (per Kg body weight)
Minimum therapeutic dose (per Kg body weight)
PENGGOLONGAN ANTIBIOTIK
BERDASARKAN DAYA KERJANYA
• ZAT BAKTERISIDA, pada dosis biasa berkhasiat mematikan
kuman
1. Zat yang bekerja pada fase tumbuh (penisilin, sefalosporin,
polipeptida, rifampisin, asam nalidiksat, kuinolon)
2. Zat yang berkerja terhadap fase istirahat (aminoglikosida,
nitrofurantoin, INH, klotrimoksazol)
• ZAT BAKTERIOSTATIK, pada dosis biasa terutama
berkhasiat menghentikan pertumbuhan dan perbanyakan
kuman (Sulfonamida, kloramfenikol, tetrasiklin, makrolida,
linkomisin)
PENGGOLONGAN ANTIBIOTIK
BERDASARKAN Spectrum of Activity
• Range of microorganisms that are affected by agent
– Broad spectrum
• Wide range, e.g. both gram-pos & gram-neg
• Used when infective bacterial agent on is not precisely
identified
– Narrow spectrum
• Limited number, or specific group of bacteria
• Used to prevent development of resistance
• Less of an affect on normal bacterial flora
Antibiotic Spectrum
Obligate intracellular microorganisms
Chlamydia – tiny, non-motile, spherical bacteria
Rickettsia – small, non-motile, gram-negative bacteria
PENGGOLONGAN ANTIBIOTIK
BERDASARKAN MEKANISME AKSI
1. Cell Wall
2. Cell membrane
3. Protein synthesis
4. Nucleic Acid Synthesis
5. Antimetabolites
Some clinically important antibiotics
Antibiotic Producer organism Activity
Site or mode of
action
Penicillin Penicillium chrysogenum Gram-positive bacteria Wall synthesis
Bacitracin Bacillus subtilis Gram-positive bacteria Wall synthesis
Polymyxin B Bacillus polymyxa Gram-negative bacteria Cell membrane
Amphotericin B Streptomyces nodosus Fungi Cell membrane
Erythromycin Streptomyces erythreus Gram-positive bacteria Protein synthesis
Neomycin Streptomyces fradiae Broad spectrum Protein synthesis
Streptomycin Streptomyces griseus Gram-negative bacteria Protein synthesis
Tetracycline Streptomyces rimosus Broad spectrum Protein synthesis
Vancomycin Streptomyces orientalis Gram-positive bacteria Protein synthesis
Rifamycin Streptomyces mediterranei Tuberculosis Protein synthesis
• Bacteria have a high internal osmotic pressure
• Without a sturdy cell wall, this pressure will cause
membrane to burst
• Antibiotics can interfere with formation of the cell wall
• Results in cell death by cell bursting open
• Sintesa dinding sel terganggu sehingga dinding menjadi
kurang sempurna dan tidak tahan terhadap tekanan
osmotis dari plasma dengan akibat pecah - DISRUPTION: GANGGUAN -STURDY: KOKOH – BURST: PECAH -INTERFERE:
MENCAMPURI
Cell Wall Disruption - Antibacterial
• Penicillin has a 4-member ring
• “looks like” part of the cell wall to the cross-linking enzyme
• Penicillin competes with the normal cell wall component for the
cross-linking enzyme, i.e. competitive inhibition
• Prevents this enzyme from cross-linking cell wall
penicillin
Cell Wall
Penicillin structure
Penicillin
• Penicillin G is the natural penicillin
– Produced by Penicillium notatum
• Administered by injection
– because is degraded by stomach acids
• Rapidly absorbed into blood & rapidly excreted
• Used against: streptococcus, meningococcus, pneumonococcus, spirochetes, clostridia, aerobic gram-positive rods, some staphylococcus and gonococcus
• Active in urine; so used for urinary tract infections
• Generally nontoxic
• Problems
– Allergic reaction (~5% in adults)
– Bacterial resistance
Semi-synthetic Penicillins
• Add a side-chain to the penicillin structure
• Alters: mengubah
– Chemical characteristics
– Spectrum of activity
– Development of bacterial resistance
• Methicillin
– Penicillinase resistant
– resistance by an different mechanism developed
• Ampicillin
– broad spectrum ( gram-neg & gram-pos)
– acid resistant, i.e. oral administration
Cephalosporins
• Produced by fungi, Cephalosporium
• ring similar to penicillins
– so action similar to penicillins
• Originally for gram-positive cocci
• Used when
– infecting bacterial strain is reistant due to penicillinase
– when allergy or toxicity to penicillin present
• Broader spectrum
• few serious side effects
– Local irritation at injection site
– Nausea, vomiting, diarrhea
– Penicillin allergic persons can also be sensitive (~15%)
β-lactam Antibiotics
Cell Wall - Polypeptide Antibiotics
• Bacitracin
– Produced by Bacillus licheniformis
– Small polypeptide
– Inhibits cell wall formation
– Used on lesions & wounds because:
• Poorly absorbed in body
• Toxic to kidneys
• Vancomycin
– Streptomyces
– Very narrow spectrum
– Used against Staphylococcus that is resistant to penicillin
– Vancomycin resistance is now developing
luka
Luka tembak
dihasilkan
Cell Wall - Antimycobacterial
• Isoniazid (INH)
– Inhibits synthesis of mycolic acid in cell wall of Mycobacteria
• Tuberculosis
– Administered with other antibiotics to prevent development of
resistance
• Ethambutanol
– Inhibits incorporation of mycolic acid into cell wall
• Rifampin (inhibits mRNA synthesis)
– Hits alternative target in cell
mencegah
• Isoniazid Complications
– Competitive inhibitor of niacin & Vitamin B6
– Prevents enzymes from converting niacin or Vitamin B6
to useful molecules
– Often supplement patient’s diet with extra Niacin &
Vitamin B6 during treatment
MEMBRAN SEL
• Molekul lipoprotein dari membran plasma ( di
dalam dinding sel) dikacaukan sintesanya
sehingga menjadi lebih permeabel.
• Hasilnya zat-zat penting dari isi sel dapat
merembes keluar.
• Contoh : polipeptida dan polyen (nistatin,
amfoterisin) dan imidazol (mikonazol,
ketokonazol)
Aminoglikosida
• Streptomisin, neomisin
• Menghambat sintesis protein
• Berikatan dengan ribosom sub unit 30S dan
mengubah bentuknya sehingga terjadi
misreading informasi yang dibawa oleh
mRNA
• Penghambatan terjadi pada tahap elongasi
Makrolid
• Eritromisin, spiramisin
• Mengikat molekul sub unit 23S rRNA
• Menghambat tahap
translokasi
Quinolon
• Ciprofloxacin
• Menghambat DNA girase (topoisomerase II)
Golongan Sulfa
• Analog PABA
• Menghambat terbentuknya THF (carrier
karbon yang digunakan dalam sintesis A, G,
T dan M)
ANTIBIOTIKA APAKAH YANG PALING TEPAT ?
3. SELEKSI ANTIBIOTIK
FAKTOR ORGANISME
TERAPI EMPIRIK SEBELUM HASIL
TES MIKROBIOLOGI, KULTUR &
SENSTIVITAS
TEMPAT INFEKSI DITEMUKAN
EFEK OBAT PADA ORGANISME
MIC, MBC
RESISTENSI ANTIBIOTIK
FAKTOR PASIEN
BERATNYA INFEKSI
STATUS IMUN
FAKTOR FARMAKOKINETIK
RIWAYAT PENYAKIT
STATUS ALERGI
FAKTOR
FARMAKOGENETIK
FAKTOR ANTIBIOTIK
SPEKTRUM AKTIVITAS ANTIBIOTIK
DOSIS, RUTE,
FREKUENSI PEMBERIAN
FARMAKOKINETIK
EFEK SINERGISTIK
INTERAKSI OBAT
EFEK SAMPING
HARGA/BIAYA
13/10/2017 27
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