PENICILLIN G POTASSIUM 
(pen-i-sill'in)
Megacillin  , Pentids
PENICILLIN G SODIUM
Classifications: antiinfective; beta-lactam antibiotic; natural penicillin
Pregnancy Category: B
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1,000,000 units, 5,000,000 units, 10,000,000 units, 20,000,000 units vials; 1,000,000 units/50 mL, 2,000,000 units/50 mL 3,000,000 units/50 mL injection
Acid-labile, penicillinase-sensitive, natural penicillin. Antimicrobial spectrum is relatively narrow compared to that of
the semisynthetic penicillins. Bactericidal at therapeutic serum levels; bacteriostatic at lower concentrations. Acts by interfering
with synthesis of mucopeptides essential to formation and integrity of bacterial cell wall. Action is inhibited by penicillinase;
therefore, penicillin G is ineffective against many strains of Staphylococcus aureus.
Highly active against gram-positive cocci (e.g., non-penicillinase-producing Staphylococcus, Streptococcus groups A, C, G, H, L, M, and Streptococcus pneumoniae); and gram-negative cocci (Neisseria gonorrhoeae, N. meningitidis). Also effective against gram-positive bacilli (Bacillus anthracis, Clostridium species including gas gangrene and tetanus, and certain species of Corynebacterium, Erysipelothrix, and Listeria); gram-negative bacilli (Fusobacterium, Pasteurella, Streptobacillus, and Bacteroides species). Parenteral penicillin G is effective against some strains of Salmonella and Shigella and spirochetes (Treponema pallidum, T. pertenue, Leptospira).
Moderate to severe systemic infections caused by penicillin-sensitive microorganisms: actinomycosis, anthrax, diphtheria (carrier
state), empyema, erysipelas, gas gangrene, gonorrheal infections, leptospirosis, mastoiditis, meningitis, acute osteomyelitis,
otitis media, pinta, pneumonia, rat-bite fever, sinus infections; certain staphylococcal infections; streptococcal infections,
including scarlet fever; syphilis (all stages), tetanus, urinary tract infections, Vincent's gingivostomatitis, yaws. Also
used as prophylaxis in patients with rheumatic or congenital heart disease. Since oral preparations are absorbed erratically
and thus must be given in comparatively high doses, this route is generally used only for mild or stabilized infections or
long-term prophylaxis.
Hypersensitivity to any of the penicillins or cephalosporins; administration of oral drug to patients with severe infections;
nausea, vomiting, hypermotility, gastric dilatation; cardiospasm. Use of penicillin G sodium in patients on sodium restriction.
Safety during pregnancy (category B) or lactation is not established.
History of or suspected allergy (asthma, eczema, hay fever, hives); history of allergy to cephalosporins; kidney or liver
dysfunction, myasthenia gravis, epilepsy, neonates, young infants. Use during lactation may lead to sensitization of infants.
Moderate to Severe Infections
Adult: PO 1.6–3.2 million U divided q6h IV/IM 1.2–24 million U divided q4h
Child: PO 25,000–100,000 U/kg divided q6h IV/IM 25,000–300,000 U/kg divided q4h
Meningococcal Meningitis
Adult: IM 1–2 million U q 2 h IV 200,000–300,000/kg/d divided q 2–4 h or 2 million to 3 million units/d by continuous infusion
Child: IV 25,000–300,000 U/kg divided q4h
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Note: Check whether physician has prescribed penicillin G potassium or sodium.
Oral
- Give on an empty stomach, at least 1 h before or 2 h after meals to reduce possibility of drug destruction by gastric acid
and delay in absorption by food.
- Give with a full glass of water. Instruct patient to avoid acidic or carbonated beverages 1 h before and after taking oral
penicillin G.
- Store tablets at 15°–30° C (59°–86° F) in tightly closed containers. Avoid excessive heat. Store
oral suspensions and syrups in refrigerator and discard unused portions after 14 d.
Intramuscular
- Do not use the 20,000,000 unit dosage form for IM injection.
- Reconstitute for IM: Loosen powder by shaking bottle before adding diluent (sterile water for injection or sterile NS). Keep
the total volume to be injected small. Solutions containing up to 100,000 units/mL cause the least discomfort. Adding 10 mL
diluent to the 1,000,000 unit vial = 100,000 units/mL. Shake well to dissolve.
- Select IM site carefully. IM injection is made deep into a large muscle mass. Inject slowly. Rotate injection sites.
| Intravenous PREPARE: Intermittent/Continuous: Reconstitute as for IM injection then withdraw the required dose and add to 100–1000 mL of D5W or NS IV solution, depending
on length of each infusion.
ADMINISTER: Intermittent/Continuous: Give intermittent infusion over at least 1 h and continuous infusion at a rate required to infuse the daily dose in 24 h.
With high doses, IV penicillin G should be administered slowly to avoid electrolyte imbalance from potassium or sodium content.
Physician will often prescribe specific flow rate.
INCOMPATIBILITIES Solution/additive:
Dextran 40,
fat emulsion,
aminophylline,
amphotericin B,
cephalothin,
chlorpromazine,
dopamine,
hydroxyzine,
metaraminol,
tetracyclines, pentobarbital,
prochlorperazine,
promazine,
sodium bicarbonate,
thiopental,
metoclopramide.
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- Store dry powder (for parenteral use) at room temperature. After reconstitution (initial dilution), store solutions for 1
wk under refrigeration. Intravenous infusion solutions containing penicillin G are stable at room temperature for at least
24 h.
Body as a Whole: Coughing, sneezing, feeling of uneasiness; systemic anaphylaxis, fever, widespread increase in capillary permeability and vasodilation with resulting edema (mouth, tongue, pharynx, larynx), laryngospasm, malaise, serum sickness (fever, malaise, pruritus, urticaria, lymphadenopathy, arthralgia, angioedema of face and extremities,
neuritis prostration, eosinophilia), SLE-like syndrome, Injection site reactions (pain, inflammation, abscess, phlebitis),
superinfections (especially with Candida and gram-negative bacteria), neuromuscular irritability (twitching, lethargy, confusion, stupor, hyperreflexia, multifocal
myoclonus, localized or generalized seizures, coma). CV: Hypotension, circulatory collapse, cardiac arrhythmias, cardiac arrest. GI: Vomiting, diarrhea, severe abdominal cramps, nausea, epigastric distress, diarrhea, flatulence, dark discoloration of tongue,
sore mouth or tongue. Urogenital: Interstitial nephritis, Loeffler's syndrome, vasculitis. Hematologic: Hemolytic anemia, thrombocytopenia. Metabolic: Hyperkalemia (penicillin G potassium); hypokalemia, alkalosis, hypernatremia, CHF (penicillin G sodium). Respiratory: Bronchospasm, asthma. Skin: Itchy palms or axilla, pruritus, urticaria, flushed skin, delayed skin rashes ranging from urticaria to exfoliative dermatitis, Stevens-Johnson syndrome, fixed-drug eruptions, contact dermatitis.
Blood grouping and compatibility tests: possible interference associated with penicillin doses greater than 20 million units daily. Urine glucose: massive doses of penicillin may cause false-positive test results with Benedict's solution and possibly Clinitest but not with glucose oxidase methods (e.g., Clinistix,
Diastix,
TesTape). Urine protein: massive doses of penicillin can produce false-positive results when turbidity measures are used (e.g., acetic acid and heat,
sulfo-salicylic acid); Ames reagent reportedly not affected. Urinary PSP excretion tests: false decrease in urinary excretion of PSP. Urinary steroids: large IV doses of penicillin may interfere with accurate measurement of urinary 17-OHCS (Glenn-Nelson technique not affected).
Drug:
Probenecid decreases renal elimination; penicillin G may decrease efficacy of oral contraceptives; colestipol decreases penicillin absorption; potassium-sparing diuretics may cause hyperkalemia with penicillin G potassium. Food: Food increases breakdown in stomach.
Absorption: 15–30% of PO dose absorbed; very acid labile. Peak: 30–60 min PO; 15–30 min IM. Distribution: Widely distributed; good CSF concentrations with inflamed meninges; crosses placenta; distributed in breast milk. Metabolism: 16–30% metabolized. Elimination: 60% excreted in urine within 6 h. Half-Life: 0.4–0.9 h.
Assessment & Drug Effects
- Obtain an exact history of patient's previous exposure and sensitivity to penicillins and cephalosporins and other allergic
reactions of any kind prior to treatment with penicillin.
- Hypersensitivity reactions are more likely to occur with parenteral penicillin but may also occur with the oral drug. Skin
rash is the most common type allergic reaction and should be reported promptly to physician.
- Lab tests: Perform C&S tests prior to initiation of therapy; treatment may be started before results are known. Evaluate renal,
hepatic, and hematologic systems at regular intervals in patients on high-dose therapy. Additionally, check electrolyte balance
periodically in patients receiving high parenteral doses.
- Observe all patients closely for at least 30 min following administration of parenteral penicillin. The rapid appearance of
a red flare or wheal at the IM or IV injection site is a possible sign of sensitivity. Also suspect an allergic reaction if
patient becomes irritable, has nausea and vomiting, breathing difficulty, or sudden fever. Report any of the foregoing to
physician immediately.
- Be aware that reactions to penicillin may be rapid in onset or may not appear for days or weeks. Symptoms usually disappear
fairly quickly once drug is stopped, but in some patients may persist for 5 d or more and require hospitalization for treatment.
- Allergy to penicillin is unpredictable. It has occurred in patients with a negative history of penicillin allergy and also
in patients with no known prior contact with penicillin (sensitization may have occurred from penicillin used commercially
in foods and beverages).
- Be alert for neuromuscular irritability in patients receiving parenteral penicillin in excess of 20 million U/d who have renal
insufficiency, hyponatremia, or underlying CNS disease, notably myasthenia gravis or epilepsy. Seizure precautions are indicated.
Symptoms usually begin with twitching, especially of face and extremities.
- Monitor I&O, particularly in patients receiving high parenteral doses. Report oliguria, hematuria, and changes in I&O ratio.
Consult physician regarding optimum fluid intake. Dehydration increases the concentration of drug in kidneys and can cause
renal irritation and damage.
- Observe closely for signs of toxicity: Neonates, young infants, the older adult, and patients with impaired kidney function
receiving high-dose penicillin therapy. Urinary excretion of penicillin is significantly delayed in these patients.
- Observe patients on high-dose therapy closely for evidence of bleeding, and bleeding time should be monitored. (In high doses,
penicillin interferes with platelet aggregation.)
Patient & Family Education
- Understand that hypersensitivity reaction may be delayed. Report skin rashes, itching, fever, malaise, and other signs of
a delayed reaction to physician immediately (see ADVERSE EFFECTS).
- Penicillin is to be taken around the clock (i.e., t.i.d. means q8h, q.i.d. means q6h, etc.). Do not miss any doses and continue
taking medication until it is all gone, unless otherwise directed by the physician.
- Measure liquid dosage form with specially marked measuring device; household teaspoons vary in size and measure.
- Notify physician if following symptoms appear when taking penicillin for treatment of syphilis (i.e., Jarisch-Herxheimer reaction
occurs 8–24 h after treatment): Headache, chills, fever, myalgia, arthralgia, malaise, and worsening of syphilitic skin
lesions. Reaction is usually self-limiting. Check with physician if symptoms do not improve within a few days or get worse.
- Report S&S of superinfection (see Appendix F).
- Understand importance of medical follow-up; present evidence suggests that glomerulonephritis, a possible complication of
streptococcal infection, may not be prevented by penicillin.
- Do not breast feed while taking this drug without consulting physician.
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