Mod 4 Flashcards by Emily S

What is selective toxicity?

Use of drugs to harm invading organisms without harming the host

Examples include antibiotics, antifungals, and antivirals.

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What are antibiotics?

Chemical substances that suppress growth of bacteria (eventually destroy them)

Accomplished via bacteriostatic or bactericidal effects.

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What is the structure of the bacterial cell wall?

Contains a peptidoglycan layer, a complex cross-linked polymer of polysaccharides and polypeptides

Cross-links provide rigidity and shape, preventing cell lysis from high osmotic pressure.

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How are bacteria classified based on their cell wall structure?

Gram-Positive Bacteria: Thick peptidoglycan layer, no outer membrane
Gram-Negative Bacteria: Thin peptidoglycan layer, yes outer membrane

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What are the two ways to classify antibiotics?

1) Spectrum of Microorganisms
* Narrow Spectrum: Only useful against particular species (ex. pencillin for gram +)
* Broad Spectrum: Effective against wide range of microorganisms (Ex. Tetracyclines)

2) Biochemical Pathway: Target and interfere with essential biochemical reactions
* cell wall inhibitors
* DNA syntheis inhibitors
* protein inhibitors
* metabolism inhibitors

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What are cell wall synthesis inhibitors?

Stop proper formation of bacterial cell wall/membrane affecting integrity

Examples include Penicillins and Cephalosporins.

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What is the mechanism of action of penicillin?

Interferes with new bacterial cell wall formation, causing cells to form without walls (protoplasts) which can easily burst

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What are the two types of penicillin?

1) Natural (penicillin G): Extracted from penicillin mould
2) Semisynthetic: Modified penicillin G, e.g., Methicillin, Ampicillin, Amoxicillin

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What are the adverse effects of penicillin?

Gastrointestinal distress, penicillin allergy, anaphylactic shock

Allergy occurs in 1-10% of the population.

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What distinguishes cephalosporins from penicillins?

Cephalosporins are chemically similar to penicillin but more resistant to penicillinase

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What are fluoroquinolones used for?

Inhibit bacterial DNA synthesis; examples include ciprofloxacin

Caused by GRAM + & - microorganisms

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What is the mechanism of action of tetracyclines?

Bind to 30S subunit of mRNA ribosome complex, preventing amino acid addition to protein chain

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What are the adverse effects of tetracyclines?

Gastrointestinal effects, discoloration of teeth, diminished bone growth

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What are metabolic inhibitors?

Block bacterial metabolic substrate formation needed for survival and reproduction

Examples include antifolate drugs (sulfonamides & trimethropim)

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What is the role of sulfonamides?

Competitively inhibit incorporation of PABA into dihydropteroic acid, blocking tetrahydrofolic acid synthesis

antifolate (inhibit metabolism)

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What is the combination antifolate therapy?

Inhibits sequential steps in metabolic pathways to produce a synergistic antibacterial effect

Example: sulfamethoxazole and trimethoprim.

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What are the factors associated with antibiotic resistance?

Evolution of bacteria, clinical and environmental factors

(overprescription, agricultural use/M cr-1 gene in pigs, inappropriate use/stopping too early)

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What are antifungals?

Drugs that inhibit synthesis of components of the fungal cell wall, causing fungal death

Examples include echinocandins and imidazoles.

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What are the types of antivirals?

1) Oseltamivir (Tamiflu)
2) Acyclovir

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What is the mechanism of action of azoles?

Inhibits P450 –> inhibit ergosterol synthesis

antifungal

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What are hormonal contraceptives?

Modify ovarian cycle

Four types: oral contraceptive, Depo-Provera, IUD, transdermal patch.

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What is the mechanism of action of hormonal contraceptives?

1) Inhibit hormone release
Hypothalamus: Doesn’t release gondatropin
Pituitary: Doesn’t release FSH or LH
2) Inhibit sperm migration (makes mucus thick)
3) Inhibit ovum implantation
(prevent endometrium from fully developing)

What are the adverse effects of oral contraceptives?

Mild: nausea, edema, headache
Moderate: breakthrough bleeding, weight gain
Serious: blood clots, heart attack, stroke, cancer

What is the depot contraceptive?

Slow-release formulation contraceptive injection every three months

What are the adverse effects of IUDs?

Heavy menstrual flow, pelvic discomfort, increased uterine infections

What are the issues with androgen-based male contraceptives?

Only 80% response rate in lowering sperm count, excess androgen enhances secondary sex characteristics

What is gossypol and its issue?

Destroys elements of seminiferous tubules, decreasing sperm production; issue is hypokalemia

Echinocandins

Inhibit compoent of cell wall | fungal

Oseltamivir

Treat influenza | anti viral

Acyclovir

Treat herpres Combat varialla-zoster virus

Antiviral

Treat already occuring infection

Virus

Can only multiply in another organijs

4 parts of resitance

1) **Uptake** (mutation/lack pores =resistance) 2) **Target** (mutation reduces binding to target) 3) **Inactivation** (enzyme that inactivates antibiotic) 4) **Efflux Pump** (too many transporters that pump out drug before it can have an effect)

types of oral contraceptives

1) fixed combo (pills) 2) multiphasic (oral) 3) progesterin only

Fixed Combo (pills) use

21-28 day cycle | fixed estrogen adn progesteron

Multiphasic (oral) use

mimic ovarian cycle | fixed estrogen, progesteron increases over time

progestin only

less common use therefore not as effective at preventing pregnancy | can cause break thorugh bleeding

Oral contraceptive adverser effects

* nausea/headaches * breathrough bleeding * skin pigmentation increase (estrogen) * acne and hisurism (progestrin) * blood clot (estrogen) * heart attack (progesterin)

Contraceptives affect on a **baby**

* deformaties * masculinization * cryptorchidism (testes dont properly descend)

Methicillin

Organism produces penicillinase → causes penicillin G resistance Methicillin RESISTANT to attack by penicillinase | semisynthetic

Ampicillin & Amoxicillin

Used against GRAM - bacteria infections (ex. urinary tract infection)

Amoxicillin & Clavulanic Acid

Semisynthetic penicillin + penicillinase inhibitor introduced to combat penicillinase-producing strains of bacteria | semisynthetic

Natural (penicillin G)

Destroys GRAM + bacteria Treatments: pneumonia, middle ear infections, skin infections, meningitis, syphilis

Penicillin mechanism of action

Related to D-alanyl-D-alanine (helps form new bacterial cell walls) Interferes with new bacterial cell wall formation

CEPHALOSPORIN Mechanism of Action

2 glycopeptide chains connect by transpeptidase enzyme → forms stable cell wall → releases D-alanine

Macrolides

Active against several bacterial infections caused GRAM + microorganisms Used if you’re allergic to penicillin | Can also treat some GRAM - bacteria (e.g. erythromycin) ## Footnote protein synthesis inhibtor (along with tetracyline)

MACROLIDES Mechanism of Action

Bind to 50S subunit on tRNA --> blocks peptide bond formation

Androgen-Based

Inhibit release of G n R H and thus spermatogenesis

Estrogens

Suppress G n R H release and thus spermatogenesis

Estrogens issues

1)Testosterone production and sex drive decreases 2)Men develop feminine characteristics

Progestin and Androgen

Synthetic progestin used to inhibit the release of G n R H → loss of spermatogenesis and testosterone production → decreases male secondary sex characteristics Androgen replaces lost testosterone → maintains the secondary sex characteristics

Transdermal Contraceptive Patch

Contains estrogen and progestin in a patch that is applied to the skin Delivered at constant rate for 7 days (3 patches/cycle)- avoiding **1st pass effect**

Intrauterine Devices (IUDs)

Implanted into uterus Most common types of IUD release levonorgestrel Can be effective for up to 8 years Useful if you want LONG-TERM, reversible contraception and estrogen isn’t recommended

what birth controls also contain estrogen

1) oral 2) transdermal