antibiotic
566 Midterm Study Guide
Week 1
-Things to know about each of the major antibiotic drug classes
Bactericidal vs. Bacteriostatic
Bactericidal antibiotics directly kill bacteria
o preferred for immunocompromised patients such as those with diabetes, HIV, or cancer & for those
who have overwhelming infections.
o Agents: aminoglycosides, beta-lactams, fluoroquinolones, metronidazole, most antimycobacterial
agents, streptogramins, & vancomycin.
Bacteriostatic agents inhibit bacterial proliferation while the host's immune system does the killing.
o Agents: clindamycin, macrolides, sulfonamides, & tetracyclines
o Bactericidal agents: “BANG Q R.I.P” - Beta-lactams, Aminoglicosides, Nitroimidazoles (Metronidazole),
Glycopeptides (Vancomycin), Quinolones, Rifampicin, Polymyxins (Colistin)
o Bacteriostatic agents: “Ms. Colt” - Macrolides, Sulfonamides, Chloramphenicol, Oxazolidinones,
Lincosamides (Clindamycin), Tetracyclines
*Bactericidal antibiotics kill bacteria directly, & bacteriostatic antibiotics stop/weaken bacteria from
growing to enable the immune system to take hold of infection*
Aminoglycosides (narrow-spectrum antibiotics used primarily against aerobic gram-negative bacilli; disrupt protein
synthesis by binding to the 30S ribosomal subunit, resulting in rapid bacterial death) (p. 683)
Examples: Gentamicin, Tobramycin, Amikacin, Neomycin, Kanamycin, Streptomycin, Paromycin, Plazomicin (p.
687)
Indications for use: Treatment of serious infections caused by gram-negative aerobic bacilli (Pseudomonas
aeruginosa, enterobacteriaceae, topical infection, ocular bacterial infections, intestinal amebiasis, complicated
UTI) (p. 687)
, Contraindications & high-risk patients : Aminoglycosides should be used with caution in patients with renal
impairment, preexisting hearing impairment, & those receiving ototoxic & nephrotoxic drugs. (pp. 685-687)
Monitoring needs: Aminoglycoside levels (peaks & troughs) & renal function must be monitored. Monitor for
neurotoxicity, ototoxicity, & nephrotoxicity.
Which ones require renal dosing adjustments and how much (i.e., 25%, 50%, etc.) : To avoid serious toxicity, we
must reduce dosage size or increase the dosing interval in patients with kidney disease. (p. 685) *Clarithromycin
Patient education: *Patients should be informed about the symptoms of vestibular & cochlear damage &
instructed to report them.
Lifespan considerations: (p. 685)
Infants: Aminoglycosides are approved to treat bacterial infections in infants younger than 8 days. Dosing is
based on weight & length of gestation.
Children/adolescents: Aminoglycosides are safe for use against bacterial infections in children & adolescents.
Pregnant women: There is evidence that use of aminoglycosides in pregnancy can harm the fetus.
Breastfeeding women: Gentamicin is probably safe to use during lactation. There is limited information
regarding its use in this way.
Older adults: Caution must be used regarding decreased renal function in the older adult.
Cephalosporins (Beta-lactam antibiotics similar in structure & actions to the penicillins; bactericidal; often resistant to
beta-lactamases, & active against a broad spectrum of pathogens; most widely used group of antibiotics) (p. 669)
Examples: 1st generation: Cephalexin (Keflex); 2nd generation: Cefoxitin, Cefaclor (Ceclor); 3rd generation:
Cefotaxime, Cefdinir, Ceftriaxone (Rocephin); 4th generation: Cefepime, 5th generation: Ceftaroline
Indications for use:
1st generation: Staphylococci or streptococci (Use in patients with mild PCN allergy, strep pharyngitis, skin
infections, & surgical prophylaxis)
2nd generation: Haemophilus influenzae, Klebsiella, pneumococci, & staphylococci (Otitis, sinusitis, & respiratory
tract infections)
3rd generation: Pseudomonas aeruginosa, Neisseria gonorrhoeae, & Klebsiella, Serratia (Meningitis, gram-
negative nosocomial infections)
4th generation: Pseudomonas aeruginosa (Hospital-acquired pneumonia & complicated intra-abdominal & UTIs
due to resistant pseudomonas)
5th generation: Methicillin-resistant Staphylococcus aureus (MRSA-associated infections). (p. 671)
Contraindications & high-risk patients : Cephalosporins are contraindicated for patients with a history of allergic
reactions to cephalosporins or severe reactions to penicillin. Patients using cefazolin & cefotetan must not
consume alcohol. Use cefotetan, cefazolin, & ceftriaxone cautiously in patients taking other agents that also
promote bleeding (anticoagulants, thrombolytics, NSAIDS, etc). (pp. 670-671)
Monitoring needs: Monitor for signs of C. dif infection & renal function in patients with renal impairment
and/or prolonged use.
Which ones require renal dosing adjustments and how much (i.e., 25%, 50%, etc.) : In patients with renal
insufficiency, dosages of most cephalosporins must be reduced to prevent accumulation to toxic levels.
(EXCEPTION: Ceftriaxone (3rd generation) is eliminated largely by the liver, so dosage reduction is unnecessary in
patients with renal impairment) (p. 669)
Patient education: *All cephalosporins can promote C. dif infection, so patients should be instructed to report
an increase in stool frequency.
Lifespan considerations:
Infants: 3rd generation cephalosporins are used to treat bacterial infections in neonates as well as infants.
Children/adolescents: Cephalosporins are commonly used to treat bacterial infections in children, including
otitis media & gonococcal & pneumococcal infections.
Pregnant women: All cephalosporins appear safe for use in pregnancy.
Breastfeeding women: Cephalosporins are generally not expected to cause adverse effects in breastfed infants.
Older adults: Doses should be adjusted in older adults with decreased renal function.
Tetracyclines (broad-spectrum antibiotics active against a wide variety of gram-positive & gram-negative bacteria;
suppress bacterial growth by binding to the 30S ribosomal subunit & inhibiting protein synthesis, extensive use has
,resulted in increasing bacterial resistance—because of this & the availability of other antibiotics with greater selectivity
& less toxicity, their use has declined & they are rarely drugs of 1 st choice) (p. 676)
Examples: Tetracycline, Demeclocycline, Doxycycline, Eravacycline, Minocycline, Omadacycline, Sarecycline
Indications for use: Treatment of tetracycline-sensitive infections, acne, & periodontal disease. 1 st line drugs for
rickettsial diseases (Rocky Mountain spotted fever, typhus fever, Q fever); infections caused by Chlamydia
trachomatis (trachoma, lymphogranuloma venereum, urethritis, cervicitis); brucellosis; cholera; pneumonia
caused by Mycoplasma pneumoniae; Lyme disease; anthrax; & gastric infection with H. pylori.
Contraindications & high-risk patients : Contraindicated in pregnant women & in children younger than 8 years.
Monitoring needs: None recommended.
Which ones require renal dosing adjustments and how much (i.e., 25%, 50%, etc.) : Tetracyclines may
exacerbate renal impairment in patients with preexisting kidney disease. Because tetracycline & demeclocycline
are eliminated by the kidneys, these agents should not be given to patients with renal impairment. If a patient
with renal impairment requires a tetracycline, either doxycycline or minocycline should be used because these
drugs are eliminated primarily by the liver. (p. 677)
Patient education: *Should not be taken with calcium supplements, milk products, iron supplements,
magnesium-containing laxatives, or most antacids because they can decrease tetracycline absorption. *GI
distress can be reduced by taking tetracycline with meals. *Advise patients to avoid prolonged exposure to
sunlight, wear protective clothing, & apply a sunscreen to exposed skin. *Patients should notify provider if
significant diarrhea occurs so that the possibility of bacterial superinfection can be evaluated. (pp. 676-678)
Lifespan considerations: (p. 678)
Children/adolescents: Tetracyclines should not be used in children younger than 8 years because they may cause
permanent discoloration of the teeth.
Pregnant women: Animal studies reveal that tetracyclines can cause fetal harm in pregnancy. Thus, this class of
drugs should be avoided in pregnant women.
Breastfeeding women: Use of tetracyclines during tooth development can cause permanent staining.
Tetracyclines should be avoided by breastfeeding women.
Older adults: Tetracyclines can interact with drugs, including digoxin. In the older adult who takes many
medications, check for interactions.
Penicillins (Beta-lactam antibiotics; active against a variety of gram-negative & gram-positive bacteria, low toxicity,
bactericidal by disrupting the synthesis of the cell wall through inhibition or transpeptidases & promoting cell wall
destruction through activating autolysins) (p. 662)
Examples:
Narrow-spectrum penicillins/penicillinase sensitive: Penicillin G, Penicillin V
Narrow-spectrum penicillins/penicillinase resistant (antistaphylococcal penicillins): Nafcillin, Oxacillin,
Dicloxacillin
Broad-spectrum penicillins (aminopenicillins): Ampicillin, Amoxicillin
Extended-spectrum penicillin (antipseudomonal penicillin): Piperacillin.
Penicillin/Beta-Lactamase combinations: Ampicillin/sulbactam (Unasyn), Amoxicillin/clavulanate (Augmentin),
Piperacillin/tazobactam (Zosyn)
Indications for use: Treatment of infections caused by sensitive bacteria.
Narrow-spectrum penicillins/penicillinase sensitive: Streptococcus, Neisseria, many anaerobes, spirochetes, &
others
Narrow-spectrum penicillins/penicillinase resistant (antistaphylococcal penicillins): Staphylococcus aureus
Broad-spectrum penicillins (aminopenicillins): Haemophilus influenzae, Escherichia coli, Proteus mirabilis,
enterococci, & Neisseria gonorrhoeae
Extended-spectrum penicillin (antipseudomonal penicillin): Same as broad-spectrum penicillins + Pseudomonas
aeruginosa, Enterobacter, Proteus, Bacteroides fragilis, & many Klebsiella
Contraindications & high-risk patients : Penicillins should be used with extreme caution in patients with a history
of severe allergic reactions to penicillins, cephalosporins, or carbapenems.
Monitoring needs: Renal impairment can cause penicillins to accumulate to toxic levels. Monitor function in
patients with renal disease.
, Which ones require renal dosing adjustments and how much (i.e., 25%, 50%, etc.) : *Amoxicillin, Augmentin,
Penicillin
Patient education:
Lifespan considerations: (p. 666)
Infants: Penicillins are used safely in infants with bacterial infections, including syphilis, meningitis, & group A
streptococcus.
Children/adolescents: Penicillins are a common drug used to treat bacterial infections in children.
Pregnant women: Although there are no well-controlled studies in pregnant women, evidence we do have
suggests there is no 2nd or 3rd trimester fetal risk.
Breastfeeding women: Amoxicillin is safe for use in breastfeeding mothers. Data are lacking regarding
transmission of some other penicillins from mother to infant through breast milk.
Older adults: Doses should be adjusted in older adults with renal dysfunction.
Sulfonamides (usually bacteriostatic; suppress bacterial growth by inhibiting the synthesis of tetrahydrofolate, a folate
derivative; broad-spectrum antimicrobials) (p. 689)
Examples: Sulfadiazine, Sulfamethoxazole, Sulfacetamide ophthalmic (Trimethoprim is NOT a sulfonamide, but it
is included here due to its same mechanism of action=suppressing the synthesis of tetrahydrofolate AND is
combined with sulfamethoxazole to form the medication Bactrim.)
Indications for use: Primarily used to treat UTIs. Other major uses are topical to treat superficial infections of the
eyes & to suppress bacterial colonization in burns. Also useful for nocardiosis, Listeria species infection, &
infection with P. jirovecii. Used as alternatives to doxycycline & erythromycin for infections caused by C.
trachomatis. Used in conjunction with pyrimethamine to treat 2 protozoal infections: toxoplasmosis & malaria
caused by chloroquine-resistant Plasmodium falciparum. Sulfasalazine is used to treat ulcerative colitis.
Contraindications & high-risk patients : Sulfonamides are contraindicated for nursing mothers, pregnant women
in the 1st trimester & also those near term, & infants younger than 2 months. An alternative antibiotic must be
chosen for patients with G6PD deficiency (can cause hemolytic anemia). Exercise caution in patients with renal
impairment—may require a reduced dosage. Trimethoprim is contraindicated in patients with folate deficiency
(manifested as megaloblastic anemia) & should be avoided when folate deficiency is likely (patients with
alcoholism & pregnant women).
Monitoring needs: *CBC should be monitored if the patient develops signs or symptoms of blood disorders, as
should CD4+ count for patients with HIV. *Signs & symptoms of hypersensitivity reactions & of resolution of
infection should also be assessed. *If hyperkalemia is suspected due to use of trimethoprim, potassium must be
checked 4 days after starting treatment. (p. 694)
Which ones require renal dosing adjustments and how much (i.e., 25%, 50%, etc.) : For patients with a
creatinine clearance (CrCl) of 15-30 mL/min, providers should prescribe 50% of the typical recommended dose. If
CrCl falls below 15 mL/min, drug must be discontinued (p. 694) *Bactrim
Patient education: *Instruct patients to complete the prescribed course of treatment even though symptoms
may abate before the full course is over. *Patients taking oral sulfonamides should drink at least 8 to 10 glasses
of water or other noncaffeinated fluids per day to decrease the risk for crystalluria. (Caffeine may be taken in
addition to the other fluids). *To prevent photosensitivity reactions, advise patients to avoid prolonged exposure
to sunlight, wear protective clothing, & apply sunscreen to exposed skin. Tanning beds should be avoided.
*Patients should be instructed to observe for alterations that may indicate hypersensitivity & report these
promptly if they occur.
Lifespan considerations:
Infants: Use of sulfonamides in infants younger than 2 months can cause kernicterus (deposition of bilirubin in
the brain—neurotoxic & can cause severe neurologic deficits & even death).
Pregnant women: Systemic sulfonamides may cause birth defects, especially if taken during the 1 st trimester. If
taken near term, the infant may develop kernicterus.
Breastfeeding women: Sulfonamides are secreted in breast milk. Breastfeeding women on sulfonamides should
be warned that breastfeeding an infant younger than 2 months can cause kernicterus.
Older adults: Older patients are more likely to experience adverse effects, & when experienced, the effects are
more likely to be severe. Life-threatening effects—including neutropenia, Stevens-Johnson syndrome, & toxic
epidermal necrolysis—occur more frequently in older adults.
