mod 5 Flashcards
Ibuprofen (Advil, Motrin, others)
Therapeutic Class: Analgesic, anti-inflammatory drug, antipyretic
Pharmacologic Class: NSAID
Actions and Uses
Ibuprofen is an older drug that is prescribed for the treatment of mild to moderate pain, fever, and inflammation. Its effectiveness is equivalent to that of aspirin and other NSAIDs. Its actions are primarily due to inhibition of prostaglandin synthesis. Common indications include pain associated with chronic musculoskeletal disorders such as RA and osteoarthritis, headache, dental pain, and dysmenorrhea. Chewable tablets, drops, and solutions are available in low doses for administration to children.
Administration Alerts
Give the drug on an empty stomach as tolerated. If nausea, vomiting, or abdominal pain occurs, give with food.
Be aware that patients with asthma or who have allergies to aspirin are more likely to exhibit a hypersensitivity reaction to ibuprofen.
Pregnancy category C. Category changes to D after 30 weeks gestation.
Adverse Effects
When used intermittently at low to moderate doses, the adverse effects of ibuprofen are generally mild and include nausea, heartburn, epigastric pain, and dizziness. GI ulceration with occult or gross bleeding may occur, especially in patients who are taking high doses for prolonged periods. Chronic use of ibuprofen may lead to renal impairment.
Black Box Warning: NSAIDs may cause an increased risk of serious thrombotic events, MI, and stroke, which can be fatal. This risk may increase with duration of use. Patients with cardiovascular disease or risk factors for cardiovascular disease may be at greater risk. NSAIDs are contraindicated for the treatment of perioperative pain in those undergoing coronary artery bypass graft surgery. NSAIDs increase the risk of serious GI adverse events including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events occur more frequently in older adults and can occur at any time during use or without warning symptoms.
Contraindications: Patients with active peptic ulcers should not take ibuprofen. This drug is also contraindicated in patients with significant renal or hepatic impairment and in those who have a syndrome of nasal polyps, angioedema, or bronchospasm due to aspirin or other NSAID use. It should be used cautiously in patients who have HF, serious HTN, or a history of stroke or MI.
Interactions
Drug–Drug: Because ibuprofen can affect platelet function, its use should be avoided when taking anticoagulants and other coagulation modifiers. Aspirin use can decrease the anti-inflammatory action of ibuprofen. The antihypertensive action of diuretics, beta blockers, and ACE inhibitors may be reduced if taken with ibuprofen. The actions of certain diuretics may be diminished when taken concurrently with ibuprofen. Use with other NSAIDs, alcohol, or corticosteroids may cause serious adverse GI events.
Lab Tests: Ibuprofen may increase bleeding time, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels. It may decrease hemoglobin and hematocrit.
Herbal/Food: Feverfew, garlic, ginger, or ginkgo may increase the risk of bleeding.
Treatment of Overdose: There is no specific treatment for overdose. Administration of an alkaline drug may increase the urinary excretion of ibuprofen.
Prednisone
Therapeutic Class: Anti-inflammatory drug
Pharmacologic Class: Corticosteroid
Actions and Uses
Prednisone is a synthetic corticosteroid. Its actions are the result of being metabolized to an active form, which is also available as a drug called prednisolone. When used for inflammation, duration of therapy is commonly limited to 4 to 10 days. For long-term therapy, alternate-day dosing is used. Prednisone is occasionally used to terminate acute bronchospasm in patients with asthma and as an antineoplastic agent for patients with certain cancers such as Hodgkin’s disease, acute leukemia, and lymphomas. It is available in tablet and oral solution forms.
Administration Alerts Administer intramuscular (IM) injections deep into the muscle mass to avoid atrophy or abscesses.
Do not use if signs of a systemic infection are present.
When using the drug for more than 10 days, the dose must be slowly tapered.
Pregnancy category C.
Adverse Effects
When used at low to moderate doses for short-term therapy, prednisone has few serious adverse effects. Long-term therapy may result in Cushing’s syndrome, a condition that includes hyperglycemia, fat redistribution to the shoulders and face, muscle weakness, bruising, and bones that easily fracture. Because gastric ulcers may occur with long-term therapy, an antiulcer medication may be prescribed prophylactically. Use with caution in patients with peptic ulcer, ulcerative colitis, or diverticulitis.
Contraindications: Patients with active viral, bacterial, fungal, or protozoan infections should not take prednisone.
Interactions
Drug–Drug: Because barbiturates, phenytoin, and rifampin increase prednisone metabolism, increased doses may be required. Concurrent use with amphotericin B or diuretics increases potassium loss, which may be serious for patients taking digoxin. Because prednisone can raise blood glucose levels, patients with diabetes may require an adjustment in the doses of insulin or oral hypoglycemic drugs.
Lab Tests: Prednisone may inhibit antibody response to toxoids and vaccines and may increase blood glucose. Serum calcium, potassium, and thyroxine may decrease.
Herbal/Food: Herbal supplements such as aloe, buckthorn, and senna may increase potassium loss. Licorice may potentiate the effect of corticosteroids. St. John’s wort may decrease prednisone levels.
Treatment of Overdose: There is no specific treatment for overdose.
Acetaminophen (Tylenol, others)
Therapeutic Class: Antipyretic and analgesic
Pharmacologic Class: Centrally acting COX inhibitor
Actions and Uses
Acetaminophen reduces fever by direct action at the level of the hypothalamus and dilation of peripheral blood vessels, which enables sweating and dissipation of heat. Acetaminophen, ibuprofen, and aspirin have equal efficacy in relieving pain and reducing fever.
Acetaminophen has no anti-inflammatory properties; therefore, it is not effective in treating arthritis or pain caused by tissue swelling following injury. The primary therapeutic usefulness of acetaminophen is for the treatment of fever in children and for relief of mild to moderate pain when aspirin is contraindicated. In the treatment of severe pain, acetaminophen may be combined with opioids. This allows the dose of opioid to be reduced, thus decreasing the risk of dependence and serious opioid toxicity. It is available as tablets, caplets, solutions, and suppositories.
Acetaminophen has no effect on platelet aggregation and does not exhibit cardiotoxicity. Most importantly, it does not cause GI bleeding or ulcers, as do the NSAIDs.
Administration Alert
Liquid forms are available in varying concentrations. Use the appropriate strength product in children to avoid toxicity.
Never administer to patients who consume alcohol regularly due to the potential for drug-induced hepatotoxicity.
Advise patients that acetaminophen is found in many OTC products and that extreme care must be taken to not duplicate doses by taking several of these products concurrently.
Pregnancy category B.
PHARMACOKINETICS Onset Peak Duration 30–60 min 0.5–2 h 4–6 h Adverse Effects Acetaminophen is generally safe, and adverse effects are uncommon at therapeutic doses. Acetaminophen causes less gastric irritation than aspirin and does not affect blood coagulation. It is not recommended in patients who are malnourished. In such cases, acute toxicity may result, leading to renal failure, which can be fatal. Other signs of acute toxicity include nausea, vomiting, chills, abdominal discomfort, and fatal hepatic necrosis.
A major concern with the use of high doses of acetaminophen is the risk for liver damage, which is especially important for patients who consume alcohol.
Black Box Warning: Acetaminophen has the potential to cause severe and even fatal liver injury and may cause serious allergic reactions with symptoms of angioedema, difficulty breathing, itching, or rash. In 2011, the FDA asked drug manufacturers to limit the strength of acetaminophen in prescription combination products to 325 mg per tablet, capsule, or dosing unit to lower the potential for acetaminophen-induced hepatotoxicity.
Contraindications: Contraindications include hypersensitivity to acetaminophen or phenacetin and chronic alcoholism.
Interactions
Drug–Drug: Acetaminophen inhibits warfarin metabolism, causing the anticoagulant to accumulate to toxic levels. High-dose or long-term acetaminophen use may result in elevated warfarin levels and bleeding. Ingestion of this drug with alcohol or other hepatotoxic drugs, such as phenytoin or barbiturates, is not recommended because of the possibility of liver failure from hepatic necrosis.
Lab Tests: Acetaminophen may increase hepatic function test values such as serum bilirubin, AST, and ALT. It may increase urinary 5-hydroxyindole acetic acid (5-HIAA) and serum uric acid.
Herbal/Food: The patient should avoid taking herbs that have the potential for liver toxicity, including comfrey, coltsfoot, and chaparral.
Treatment of Overdose: The specific treatment for overdose is the oral or intravenous (IV) administration of N-acetylcysteine (Acetadote) as soon as possible after the overdose. This drug protects the liver from toxic metabolites of acetaminophen.
Hepatitis B Vaccine (Engerix-B, Recombivax HB)
Therapeutic Class: Vaccine
Pharmacologic Class: Vaccine
Actions and Uses
Hepatitis B vaccine is used to provide active immunity in individuals who are at risk for exposure to hepatitis B virus (HBV). It is indicated for infants born to mothers who are HBV-positive and those at high risk for exposure to HBV-infected blood, including nurses, health care providers, dentists, dental hygienists, morticians, and paramedics. Because HBV infection is extremely difficult to treat, it is prudent for all health care workers to receive the HBV vaccine before beginning their clinical education, if not already vaccinated, unless contraindicated. The vaccine is also indicated for all persons who engage in high-risk sexual practices such as heterosexual activity with multiple partners, prostitution, or homosexual or bisexual activities, and for persons who repeatedly contract sexually transmitted infections. Other recommended groups include sexually active adolescents, dialysis patients, prisoners in correctional facilities, anyone living or traveling for more than 6 months where HBV is common, and subpopulations with known high rates of infection such as Alaskan natives, Pacific Islanders, and refugees from areas where the infection is endemic. HBV vaccine does not provide protection against exposure to other (non-B) hepatitis viruses. HBV vaccine is produced through recombinant DNA technology using yeast cells. It is not prepared from human blood.
HBV vaccination requires three intramuscular (IM) injections; the second dose is given 1 month after the first, and the third dose 6 months after the first dose. The drug is over 90% effective in providing immunity to HBV. The effectiveness of the vaccine in producing immunity in adults declines with age.
Administration Alerts
In adults, use the deltoid muscle for the injection site, unless contraindicated.
Because none of the formulas of Recombivax HB contain a preservative, once the single-dose vial has been penetrated, the withdrawn vaccine should be used promptly, and the vial discarded.
Epinephrine (1:1,000) should be immediately available to treat a possible anaphylactic reaction.
Pregnancy category C.
Adverse Effects
The most common adverse effects from HBV vaccination are pain at the injection site and mild to moderate fever and chills. Approximately 15% of patients will experience minor symptoms such as fatigue, dizziness, fever, and headache. Hypersensitivity reactions such as urticaria or anaphylaxis are possible.
Contraindications: This vaccine is contraindicated in patients with hypersensitivity to yeast or HBV vaccine. Patients who demonstrated severe hypersensitivity to the first dose of the vaccine should not receive subsequent doses. The drug should be administered with caution in patients with fever or active infections, or those with compromised cardiopulmonary status. The vaccine should be given to pregnant or lactating women only if clearly needed to protect the health of the mother or child.
Interactions
Drug–Drug: Immunosuppressants will decrease the effectiveness of the HBV vaccine.
Lab Tests: Unknown.
Herbal/Food: Unknown.
Treatment of Overdose: Overdoses have not been recorded.
Interferon alfa-2b (Intron-A)
Therapeutic Class: Immunostimulant
Pharmacologic Class: Interferon, biologic response modifier
Actions and Uses
Interferon alfa-2b is a biologic response modifier prepared by recombinant DNA technology that is approved to treat cancers (hairy cell leukemia, malignant melanoma, non-Hodgkin’s lymphoma, AIDS-related Kaposi’s sarcoma) as well as viral infections (human papillomavirus, chronic hepatitis virus B and C). Off-label indications may include chronic myelogenous leukemia, bladder cancer, herpes simplex virus, renal cell cancer, varicella-zoster virus, and West Nile virus. It is available for IV, IM, and subcutaneous administration. For treating condylomata acuminata (genital warts) the drug is injected directly into the lesion 3 times a week for 3 weeks.
Peginterferon alfa-2b (PegIntron) has a molecule of PEG attached to the interferon molecule, which gives the drug an extended half-life. Peginterferon alfa-2b (PegIntron) is approved in combination with ribavirin to treat chronic hepatitis C virus infections. In 2011, peginterferon alfa-2b (Sylatron) was approved to treat melanoma.
Administration Alerts
The drug should be administered under the careful guidance of a health care provider experienced with its use.
Subcutaneous administration is recommended for patients at risk for bleeding (platelet count less than 50,000/mm3).
Pregnancy category C.
Adverse Effects
A flulike syndrome of fever, chills, dizziness, and fatigue occurs in 50% of patients, although this usually diminishes as therapy progresses. Headache, nausea, vomiting, diarrhea, and anorexia are relatively common. Depression and suicidal ideation have been reported and may be severe enough to require discontinuation of the drug. With prolonged therapy, serious toxicity such as immunosuppression, hepatotoxicity, and neurotoxicity may be observed.
Black Box Warning: IFNs may cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, or infectious disorders.
Contraindications: Contraindications include hypersensitivity to IFNs, autoimmune hepatitis, and hepatic decompensation. Neonates and infants should not receive this drug because it contains benzyl alcohol, which is associated with an increased incidence of neurologic and other serious complications in these age groups.
Interactions
Drug–Drug: Use with ethanol may cause excessive drowsiness and dehydration. There is additive myelosuppression with antineoplastics. Zidovudine may increase hematologic toxicity.
Lab Tests: Large declines in hematocrit, leukocyte counts, and platelet counts may occur after 3–5 days of therapy. Hepatic enzymes may become elevated during IFN therapy and may require discontinuation of the drug. Interferon alfa-2b may elevate triglyceride levels.
Herbal/Food: Unknown.
Treatment of Overdose: Overdose may cause lethargy and coma. Treatment is by general supportive measures.
Cyclosporine (Gengraf, Neoral, Sandimmune)
Therapeutic Class: Immunosuppressant
Pharmacologic Class: Calcineurin inhibitor
Actions and Uses
Cyclosporine is a complex chemical obtained from a soil fungus that inhibits helper T cells. Compared to some of the other immunosuppressants, cyclosporine is less toxic to bone marrow cells. When prescribed for transplant recipients, it is often used in combination with high doses of a corticosteroid such as prednisone. Cyclosporine is approved for the prophylaxis of kidney, heart, and liver transplant rejection; psoriasis; and xerophthalmia, an eye condition of diminished tear production caused by ocular inflammation. An IV form is available for transplant rejection and for severe cases of ulcerative colitis or Crohn’s disease.
Administration Alerts
Neoral (microemulsion) and Sandimmune are not bioequivalent and cannot be used interchangeably without close supervision by the health care provider.
Pregnancy category C.
Adverse Effects
The primary adverse effect of cyclosporine occurs in the kidneys, with up to 75% of patients experiencing reduction in urine output. Over half the patients taking the drug will experience hypertension and tremor. Other common side effects are headache, gingival hyperplasia, and elevated hepatic enzymes. Periodic blood counts are necessary to ensure that WBCs do not fall below 4,000, or platelets below 75,000. Long-term therapy increases the risk of malignancy, especially lymphomas and skin cancers.
Black Box Warning: This drug should only be administered by health care providers experienced in immunosuppressive therapy. Use may result in serious infections and possible malignancies. Renal function should be monitored during therapy.
Contraindications: The only contraindication is prior hypersensitivity to the drug.
Interactions
Drug–Drug: Drugs that decrease cyclosporine levels include phenytoin, phenobarbital, carbamazepine, and rifampin. Azole antifungal drugs, angiotensin-converting enzyme (ACE) inhibitors, nonsteroidal anti-inflammatory drugs (NSAIDs), and macrolide antibiotics may increase cyclosporine levels.
Lab Tests: Cyclosporine may increase serum triglycerides and uric acid. It may decrease hepatic enzymes and urinary function test values.
Herbal/Food: Food decreases the absorption of the drug. Grapefruit juice can raise cyclosporine levels by 50–200%. This drug should be used with caution with herbal immune-stimulating supplements such as astragalus and echinacea, which may interfere with immunosuppressants.
Treatment of Overdose: There is no specific treatment for overdose.
Penicillin G
Therapeutic Class: Antibacterial
Pharmacologic Class: Cell wall inhibitor; natural penicillin
Actions and Uses
Similar to penicillin V, penicillin G is a drug of choice against streptococci, pneumococci, and staphylococci organisms that do not produce penicillinase and are shown to be susceptible by C&S testing. It is also a medication of choice for gonorrhea and syphilis caused by susceptible strains. Penicillin G is available as either a potassium or sodium salt; there is no difference therapeutically between the two salts. Penicillin G benzathine (Bicillin) and penicillin G procaine (Wycillin) are longer acting parenteral salts of the drug.
Only 15–30% of an oral dose of penicillin G is absorbed. Because of its low oral absorption, penicillin G is often given by the intravenous (IV) or intramuscular (IM) routes. Penicillin V and amoxicillin are more stable in acid and are used when oral penicillin therapy is desired. Penicillinase-producing organisms inactivate both penicillin G and penicillin V.
Administration Alerts
After parenteral administration, observe for possible allergic reactions for 30 minutes, especially following the first dose.
Do not mix penicillin and aminoglycosides in the same IV solution. Give IV medications 1 hour apart to prevent interactions.
Pregnancy category B.
Adverse Effects
Penicillin G has few serious adverse effects. Diarrhea, nausea, and vomiting are the most common adverse effects and can be serious in children and older adults. Pain at the injection site may occur, and superinfections are possible. Anaphylaxis is the most serious adverse effect. While most allergic reactions to penicillin occur within minutes after administration, late hypersensitivity reactions may occur several weeks into the regimen.
Contraindications: The only contraindication is hypersensitivity to a drug in the penicillin class. Because penicillin G is excreted extensively by the kidneys, the drug should be used with caution in patients with severe renal disease.
Interactions
Drug–Drug: Penicillin G may decrease the effectiveness of oral contraceptives. Colestipol taken with this medication will decrease the absorption of penicillin. Potassium-sparing diuretics may cause hyperkalemia when administered with penicillin G potassium. Because penicillins can antagonize the actions of aminoglycoside antibiotics, drugs from these two classes are not administered concurrently.
Lab Tests: Penicillin G may give positive Coombs’ test and false positive urinary or serum proteins.
Herbal/Food: Unknown.
Treatment of Overdose: There is no specific treatment for overdose.
Cefazolin (Ancef, Kefzol)
Therapeutic Class: Antibacterial
Pharmacologic Class: Cell wall inhibitor: first-generation cephalosporin
Actions and Uses
Cefazolin is a beta-lactam antibiotic used for the treatment and prophylaxis of bacterial infections, particularly those that are caused by susceptible gram-positive organisms. Cefazolin has been used to treat infections of the respiratory tract, urinary tract, skin structures, biliary tract, bones, and joints. It has also been useful in the pharmacotherapy of genital infections, septicemia, and endocarditis. Cefazolin is not effective against MRSA.
This drug is sometimes used for infection prophylaxis in patients who are undergoing surgical procedures. Cefazolin has a longer half-life than other first-generation cephalosporins, which allows for less frequent dosing. It is one of the most frequently prescribed parenteral antibiotics.
Administration Alerts
Administer IM injections deep into a large muscle mass to prevent injury to surrounding tissues.
Pregnancy category B.
Adverse Effects
The cephalosporins are well tolerated by most patients. Rash and diarrhea are the most common adverse effects, and superinfections are likely when the antibiotic is used for prolonged periods. Approximately 1% to 4% of patients will experience some kind of an allergic reaction. Severe hypersensitivity reactions are rare, though potentially fatal. Pain and phlebitis can occur at IM injection sites. Seizures are a rare, though potentially serious, adverse effect of cephalosporin therapy.
Contraindications: The only contraindication is hypersensitivity to a drug in the cephalosporin class. Because cefazolin is extensively excreted by the kidneys, the drug should be used with caution in patients with severe renal disease.
Interactions
Drug–Drug: Concurrent use of cefazolin with nephrotoxic drugs, such as aminoglycosides or vancomycin, increases the risk of nephrotoxicity. Cefazolin may have additive or synergistic antimicrobial action with other antibiotics such as aztreonam, carbapenems, and the penicillins. The anticoagulant effect of warfarin may be increased if given concurrently with cefazolin.
Lab Tests: False positive urine glucose results are possible; may give a positive Coomb’s test.
Herbal/Food: Unknown.
Treatment of Overdose: There is no specific treatment for overdose.
Tetracycline (Sumycin, others)
Therapeutic Class: Antibacterial
Pharmacologic Class: Tetracycline; protein synthesis inhibitor
Actions and Uses
Tetracycline is effective against a broad range of gram-positive and gram-negative 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 PO, 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 a full glass of water to decrease esophageal and GI irritation.
Administer antacids and tetracycline 1 to 3 hours apart.
Pregnancy category D.
Adverse Effects
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. Tetracycline should not be given concurrently with acitretin because the combination can increase intracranial pressure. Concurrent use with lomitapide is contraindicated because tetracyclines will increase serum levels of lomitapide several fold.
Lab Tests: May increase the following laboratory 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.
The newest of the tetracyclines, tigecycline (Tygacil), is indicated for drug-resistant intra-abdominal infections and complicated skin and skin-structure infections, especially those caused by MRSA. Nausea and vomiting may be severe with this drug. Tigecycline is available by IV infusion.
Erythromycin (Eryc, Erythrocin, others)
Therapeutic Class: Antibacterial
Pharmacologic Class: Macrolide; protein synthesis inhibitor
Actions and Uses
Erythromycin is inactivated by stomach acid and is thus formulated as coated, acid-resistant tablets or capsules that dissolve in the small intestine. Its main application is for patients who are unable to tolerate penicillins or who may have a penicillin-resistant infection. It has a spectrum similar to that of the penicillins and is effective against most gram-positive bacteria. It is sometimes used to treat susceptible infections by Bordetella pertussis (whooping cough), Legionella pneumophila (Legionnaires’ disease), M. pneumoniae, and Corynebacterium diphtheriae.
Administration Alerts
Administer oral drug on an empty stomach with a full glass of water.
For suspensions, shake the bottle thoroughly to ensure that the drug is well mixed.
Do not give with or immediately before or after fruit juices.
Pregnancy category B.
Adverse Effects
The most frequent adverse effects from erythromycin are nausea, abdominal cramping, and vomiting, although these are rarely serious enough to cause discontinuation of therapy. Concurrent administration with food reduces these symptoms. Hearing loss, vertigo, and dizziness may be experienced when using high doses, particularly in older adults and in those with impaired hepatic or renal excretion. High doses of IV erythromycin may be cardiotoxic and pose a risk for potentially fatal dysrhythmias.
Contraindications: Erythromycin is contraindicated in patients with hypersensitivity to drugs in the macrolide class and for those who are taking terfenadine, astemizole, or cisapride.
Interactions
Drug–Drug: Anesthetics, azole antifungals, and anticonvulsants may interact to cause serum drug levels of erythromycin to rise and result in toxicity. This drug interacts with cyclosporine, increasing the risk for nephrotoxicity. It may increase the effects of warfarin. The concurrent use of erythromycin with lovastatin or simvastatin is not recommended because it may increase the risk of muscle toxicity. Ethanol use may decrease the absorption of erythromycin.
Lab Tests: Erythromycin may interfere with AST and give false urinary catecholamine values.
Herbal/Food: St. John’s wort may decrease the effectiveness of erythromycin.
Treatment of Overdose: There is no specific treatment for overdose.
Gentamicin (Garamycin, others)
Therapeutic Class: Antibacteriall
Pharmacologic Class: Aminoglycoside; protein synthesis inhibitor
Actions and Uses
Gentamicin is a broad-spectrum, bactericidal antibiotic usually prescribed for serious urinary, respiratory, nervous, or GI infections when less toxic antibiotics are contraindicated. Activity includes Enterobacter, E. coli, Klebsiella, Citrobacter, Pseudomonas, and Serratia. Gentamicin is effective against a few gram-positive bacteria, including some strains of MRSA. It is often used in combination with other antibiotics such as penicillins or cephalosporins. This drug is not absorbed by the oral route. A topical formulation (Genoptic) is available for infections of the external eye.
Administration Alerts
For IM administration, inject deep into a large muscle.
Use only IM and IV drug solutions that are clear and colorless or slightly yellow. Discard discolored solutions or those that contain particulate matter.
Withhold the drug if the peak serum level lies above the normal range of 5–10 mcg/mL.
Pregnancy category C.
Adverse Effects
Rash, nausea, vomiting, and fatigue are the most frequent adverse effects. As with other aminoglycosides, certain adverse effects may be severe. Resistance to gentamicin is increasing, and some cross resistance among aminoglycosides has been reported.
Black Box Warnings: Adverse effects from parenteral gentamicin may be severe and include the following:
Neurotoxicity may manifest as ototoxicity and produce a loss of hearing or balance, which may become permanent with continued use. Tinnitus, vertigo, and persistent headaches are early signs of ototoxicity. The risk of neurologic effects is higher in patients with impaired renal function. Other signs of neurotoxicity include paresthesias, muscle twitching, and seizures. Concurrent use with other neurotoxic drugs should be avoided.
Neuromuscular blockade and respiratory paralysis are possible and the drug may cause severe neuromuscular weakness that lasts for several days.
Nephrotoxicity is possible. Signs of reduced kidney function include oliguria, proteinuria, and elevated BUN and creatinine levels. Nephrotoxicity is of particular concern to patients with pre-existing kidney disease and may limit pharmacotherapy. Concurrent use with other nephrotoxic drugs should be avoided.
Contraindications: Gentamicin is contraindicated in patients with hypersensitivity to drugs in the aminoglycoside class. Drug therapy must be monitored carefully in patients with impaired renal function or those with pre-existing hearing loss.
Interactions
Drug–Drug: The risk of ototoxicity increases if the patient is currently taking amphotericin B, furosemide, aspirin, bumetanide, ethacrynic acid, cisplatin, or paromomycin. Concurrent use with amphotericin B, capreomycin, cisplatin, polymyxin B, or vancomycin increases the risk of nephrotoxicity.
Lab Tests: Gentamicin may increase values of the following: serum bilirubin, serum creatinine, serum lactate dehydrogenase (LDH), BUN, AST, or ALT; may decrease values for the following: serum calcium, sodium, or potassium.
Herbal/Food: Unknown.
Treatment of Overdose: There is no specific treatment for overdose.
Ciprofloxacin (Cipro)
Therapeutic Class: Antibacterial
Pharmacologic Class: Fluoroquinolone; bacterial DNA synthesis inhibitor
Actions and Uses
Ciprofloxacin, a second-generation fluoroquinolone, is the most widely prescribed drug in this class. By inhibiting bacterial DNA gyrase, ciprofloxacin affects bacterial replication and DNA repair. More effective against gram-negative than gram-positive organisms, it is prescribed for UTI, sinusitis, pneumonia, skin, bone and joint infections, infectious diarrhea, and certain eye infections. As of 2007, the FDA recommended that ciprofloxacin no longer be used to treat gonorrhea. The drug is rapidly absorbed after PO administration and is distributed to most body tissues. Oral, IV, ophthalmic, and otic formulations are available. An extended-release form of the drug, Proquin XR, is administered for only 3 days and is approved for bladder infections.
Administration Alerts
Administer at least 4 hours before antacids and ferrous sulfate.
Pregnancy category C.
Adverse Effects
Ciprofloxacin is well tolerated by most patients, and serious adverse effects are uncommon. Nausea, vomiting, and diarrhea may occur in as many as 20% of patients. Ciprofloxacin may be administered with food to diminish adverse GI effects. The patient should not, however, take this drug with antacids or mineral supplements because drug absorption will be diminished. Some patients report phototoxicity, headache, and dizziness.
Black Box Warning: Tendinitis and tendon rupture may occur in patients of all ages. Risk is especially high in patients over age 60; in kidney, heart, and lung transplant recipients; and in those receiving concurrent corticosteroid therapy. Fluoroquinolones may cause extreme muscle weakness in patients with myasthenia gravis.
Contraindications: Ciprofloxacin is contraindicated in patients with hypersensitivity to drugs in the fluoroquinolone class. The drug should be discontinued if the patient experiences pain or inflammation of a tendon because tendon ruptures have been reported.
Interactions
Drug–Drug: Concurrent administration with warfarin may increase anticoagulant effects and result in bleeding. This drug may increase theophylline levels. Antacids, ferrous sulfate, and sucralfate decrease the absorption of ciprofloxacin.
Lab Tests: Ciprofloxacin may increase values of ALT, AST, serum creatinine, and BUN.
Herbal/Food: Ciprofloxacin can increase serum levels of caffeine; caffeine consumption should be restricted to prevent excessive nervousness, anxiety, or tachycardia. Dairy products or calcium-fortified drinks can decrease the absorption of ciprofloxacin.
Treatment of Overdose: There is no specific treatment for overdose.
Trimethoprim–Sulfamethoxazole (Bactrim, Septra)
Therapeutic Class: Antibacterial
Pharmacologic Class: Sulfonamide; folic acid inhibitor
Actions and Uses
The fixed-dose combination of sulfamethoxazole (SMZ) with the anti-infective trimethoprim (TMP) is most frequently prescribed for the pharmacotherapy of UTIs. It is also approved for the treatment of Pneumocystis carinii pneumonia, shigella infections of the small bowel, and for acute episodes of chronic bronchitis. Oral and IV preparations are available.
Both SMZ and TMP are inhibitors of the bacterial metabolism of folic acid. Their action is synergistic: A greater bacterial kill is achieved by the fixed combination than would be achieved with either drug used separately. Because humans obtain the precursors of folate in their diets and can use preformed folate, these medications are selective for bacterial metabolism. Another advantage of the combination is that development of resistance is lower than is observed when either of the agents is used alone.
Administration Alerts
Administer oral dosages with a full glass of water.
Pregnancy category C.
Adverse Effects
Nausea and vomiting are the most frequent adverse effects of TMP-SMZ therapy. Hypersensitivity is relatively common and usually manifests as skin rash, itching, and fever. This medication should be used cautiously in patients with pre-existing kidney disease, because crystalluria, oliguria, and renal failure have been reported. Periodic laboratory evaluation of the blood is usually performed to identify early signs of agranulocytosis or thrombocytopenia. Due to the potential for photosensitivity, the patient should avoid direct sunlight during therapy.
Contraindications: TMP-SMZ is contraindicated in patients with hypersensitivity to drugs in the sulfonamide class. Patients with documented megaloblastic anemia due to folate deficiency should not receive this drug. Pregnant women at term and nursing mothers should not take this drug because sulfonamides may cross the placenta and are excreted in milk and may cause kernicterus. Trimethoprim decreases potassium excretion and should be used with caution in patients with hyperkalemia.
Interactions
Drug–Drug: TMP-SMZ may enhance the effects of certain anticoagulants, resulting in serious or life-threatening interactions. These drugs may also increase methotrexate toxicity. By decreasing the hepatic metabolism of phenytoin, TMP-SMZ may cause phenytoin toxicity. TMP-SMZ exerts a potassium-sparing effect on the nephron and should be used with caution with diuretics such as spironolactone (Aldactone) to prevent hyperkalemia.
Lab Tests: Unknown.
Herbal/Food: Potassium supplements should not be taken during therapy, unless directed by the health care provider.
Treatment of Overdose: The renal elimination of trimethoprim can be increased by acidification of the urine. If signs of bone marrow suppression occur during high-dose therapy, 5 to 15 mg of leucovorin should be given daily.
Isoniazid (INH)
Therapeutic Class: Antituberculosis drug
Pharmacologic Class: Mycolic acid inhibitor
Actions and Uses
Isoniazid is a first-line drug for the treatment of M. tuberculosis. This is because decades of experience have shown it to have a superior safety profile and to be the most effective, single drug for the infection. Isoniazid acts by inhibiting the synthesis of mycolic acids, which are essential components of mycobacterial cell walls. It is bactericidal for actively growing organisms but bacteriostatic for dormant mycobacteria. It is selective for M. tuberculosis. INH may be used alone for chemoprophylaxis, or in combination with other antituberculosis drugs for treating active disease. Approximately 10% of patients will develop resistance to INH during long-term therapy.
Administration Alerts
Give on an empty stomach, 1 hour after or 2 hours before meals.
For IM administration, inject deep IM, and rotate sites.
Pregnancy category C.
Adverse Effects
The most common adverse effects of INH are numbness of the hands and feet, rash, and fever. Neurotoxicity is a concern during therapy, and patients may exhibit paresthesia of the feet and hands, convulsions, optic neuritis, dizziness, coma, memory loss, and various psychoses.
Black Box Warning: Although rare, hepatotoxicity is a serious and sometimes fatal adverse effect; thus, the patient should be monitored carefully for jaundice, fatigue, elevated hepatic enzymes, or loss of appetite. Liver enzyme tests are usually performed monthly during therapy to identify early hepatotoxicity. Hepatotoxicity usually appears in the first 1 to 3 months of therapy but may occur at any time during treatment. Older adults and those with daily alcohol consumption are at greater risk of developing hepatotoxicity.
Contraindications: Isoniazid is contraindicated in patients with hypersensitivity to the drug and in patients with severe hepatic impairment.
Interactions
Drug–Drug: Aluminum-containing antacids should not be administered concurrently because they can decrease the absorption of INH. When disulfiram is taken with INH, lack of coordination or psychotic reactions may result. Drinking alcohol with INH increases the risk of hepatotoxicity. INH may increase serum levels of phenytoin and carbamazepine.
Lab Tests: INH may increase values of AST and ALT.
Herbal/Food: Food interferes with the absorption of INH. Foods containing tyramine may increase INH toxicity.
Treatment of Overdose: INH overdose may be fatal. Treatment is mostly symptomatic. Pyridoxine (vitamin B6) may be infused in a dose equal to that of the INH overdose to prevent seizures and to correct metabolic acidosis. The dose may be repeated several times until the patient regains consciousness.
