Antimicrobial Drugs

M34_ADAM9811_03_SE_CH34.QXD 12/30/09 1:16 PM Page 488
488 Unit 5 The Immune System
TABLE 34. 4 Tetracyclines
Drug Route and Adult Dose (max dose where indicated) Adverse Effects
demeclocycline (Declomycin) PO; 150 mg every 6 h or 300 mg every 12 h (max: 2.4 g/day) Nausea, vomiting, abdominal cramping, flatulence,
doxycycline (Vibramycin, others)
PO/IV; 100 mg bid on day 1, then 100 mg/day (max: 200 mg/day)
diarrhea, mild phototoxicity, rash, dizziness,
stinging/burning with topical applications
minocycline (Minocin, others)
PO/IV; 200 mg as single dose followed by 100 mg bid
Anaphylaxis, secondary infections, hepatotoxicity,
tetracycline (Sumycin, others)
PO; 250–500 mg bid–qid (max: 2 g/day)
exfoliative dermatitis
tigecycline (Tygacil)
IV; 100 mg, followed by 50 mg every 12 h
Italics indicate common adverse effects; underlining indicates serious adverse effects.
against a large number of different gram-negative and
gram-positive organisms and have one of the broadest spectrums
of any class of antibiotics. The tetracyclines are listed
in Table 34.4.
34.10 Pharmacotherapy
with Tetracyclines
Tetracyclines act by inhibiting bacterial protein synthesis. By
binding to the bacterial ribosome, which differs in structure
from a human ribosome, the tetracyclines slow microbial
growth and exert a bacteriostatic effect. All tetracyclines
have the same spectrum of activity and exhibit similar adverse
effects. Doxycycline (Vibramycin, others) and minocycline
(Minocin, others) have longer durations of actions and
are more lipid soluble, permitting them to enter the CSF.
The widespread use of tetracyclines in the 1950s and 1960s
resulted in the emergence of a large number of resistant bacterial
strains that now limit their therapeutic utility. They are
drugs of choice for only a few diseases: Rocky Mountain spotted
fever, typhus, cholera, Lyme disease, peptic ulcers caused
by Helicobacter pylori, and chlamydial infections. Drugs in
this class are occasionally used for the treatment of acne vulgaris,
for which they are given topically or PO at low doses.
Tetracyclines exhibit few serious adverse effects. Gastric
distress is relatively common with tetracyclines, however,
and patients will tend to take tetracyclines with food. Because
these drugs bind metal ions such as calcium and iron,
Prototype Drug
Therapeutic Class: Antibacterial
❘ Tetracycline (Sumycin, others)
Pharmacologic Class: Tetracycline; protein synthesis inhibitor
ACTIONS AND USES
ADVERSE EFFECTS
Tetracycline is effective against a broad range of gram-positive and gramnegative
organisms, including Chlamydia, Rickettsiae, and Mycoplasma. Its use
has increased over the past decade due to its effectiveness against H. pylori in
the treatment of peptic ulcer disease.Tetracycline is given orally, though it has a
short half-life that may require administration four times per day. Topical and
oral preparations are available for treating acne. An IM preparation is available;
injections may cause local irritation and be extremely painful.
ADMINISTRATION ALERTS
■ Administer oral drug with full glass of water to decrease esophageal and GI
irritation.
■ Administer antacids and tetracycline 1 to 3 hours apart.
■ Administer antilipidemic agents at least 2 hours before or after tetracycline.
■ Pregnancy category D
PHARMACOKINETICS
Onset: 1–2 h
Peak: 2–4 h
Half-life: 6–12 h
Duration: 12 h
Being a broad-spectrum antibiotic,tetracycline has a tendency to affect vaginal,
oral, and intestinal flora and cause superinfections. Tetracycline irritates the GI
mucosa and may cause nausea,vomiting,epigastric burning,and diarrhea.Diarrhea
may be severe enough to cause discontinuation of therapy.Other common
side effects include discoloration of the teeth and photosensitivity.
Contraindications: Tetracycline is contraindicated in patients with hypersensitivity
to drugs in this class.The drug should not be used during the second half
of pregnancy, in children 8 years or younger, and in patients with severe renal or
hepatic impairment.
INTERACTIONS
Drug–Drug: Milk products, iron supplements, magnesium-containing laxatives, and
antacids reduce the absorption and serum levels of tetracyclines.Tetracycline binds
with the lipid-lowering drugs colestipol and cholestyramine, thereby decreasing the
antibiotic’s absorption.This drug decreases the effectiveness of oral contraceptives.
Lab Tests: May increase the following lab values: blood urea nitrogen (BUN),
aspartate aminotransferase (AST), alanine aminotransferase (ALT), amylase, bilirubin,
and alkaline phosphatase.
Herbal/Food: Dairy products interfere with tetracycline absorption.
Treatment of Overdose: There is no specific treatment for overdose.
Refer to MyNursingKit for a Nursing Process Focus specific to this drug.
# 102887 Cust: PE/NJ/CHET Au: ADAMS Pg. No. 488
Title: Pharmacology for Nurses Server: Jobs2
C/M/Y/K
Short / Normal
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