Pharmacology Chapter 41- Antitubercular Drugs

Tuberculosis is spread through ____________ ___________.

Respiratory droplets

Interactions and contraindications for Isoniazid (INH)

*Interactions*- - Phenytoin and carbamazepine (anticonvulsants): increased effect- sedation. - Antacids: decreased absorption of INH. - TB meds: Rifampin and ethionamide: increased hepatotoxicity. - Alcohol: increased metabolism of INH = decreased effectiveness. *Contraindications*- - renal or liver dysfunction.

Rifapentine (Priftin)

A derivative of rifampin. Offers an advantage over rifampin, because it has a much longer duration of action and possibly better efficacy. Accumulates (builds up) in the tissues, allowing it to work longer. *Adverse effects*- GI upset, discolors body fluids red.

While monitoring a patient, the nurse knows that a therapeutic response to antitubercular drugs would be- A. The patient states that he or she is feeling much better. B. The patient's laboratory test results show a lower white blood cell count. C. The patient reports a decrease in cough and night sweats. D. There is a decrease in symptoms, along with improved chest x-ray and sputum culture results.

D. There is a decrease in symptoms, along with improved chest x-ray and sputum culture results.

The nurse is explaining antitubercular therapy to a patient. The patient asks, "Why do I have to take so many different medications?" What is the nurse's best response? A. "It helps to prevent the tuberculosis from becoming resistant to the drugs." B. "It makes sure that the disease is cured." C. "These medications will reduce symptoms immediately." D. "You will have fewer side effects."

A. "It helps to prevent the tuberculosis from becoming resistant to the drugs."

The nurse is counseling a woman who is beginning antitubercular therapy with rifampin. The patient also takes an oral contraceptive. Which statement by the nurse is most accurate regarding potential drug interactions? A. "You will need to switch to another form of birth control while you are taking the rifampin." B. "Your birth control pills will remain effective while you are taking the rifampin." C. "You will need to take a stronger dose of birth control pills while you are on the rifampin." D. "You will need to obstain from sexual inter course while on the rifampin to avoid pregnancy."

A. "You will need to switch to another form of birth control while you are taking the rifampin."

The nurse is reviewing the medication list of a patient who has been newly diagnosed with tuberculosis and will be taking rifampin (Rifadin). Which class of drugs, if taken with rifampin, may cause increased metabolism? (Select all that apply) A. Beta blockers B. Proton pump inhibitors C. Selective serotonin reuptake inhibitors D. Oral anticoagulants E. Oral antidiabetic drugs

A. Beta blockers D. Oral anticoagulants E. Oral antidiabetic drugs

The nurse would correctly identify the method of action of ethambutol (Myambutol) as which of the following? A. Inhibiting protein synthesis. B. Inhibiting mycobacterial ATP synthase. C. Altering cell wall synthesis. D. Its method of action is unknown.

A. Inhibiting protein synthesis.

A patient will be receiving long-term isoniazid (INH) therapy. What laboratory tests are most important for the nurse to monitor during therapy? A. Liver enzyme levels. B. Hematocrit and hemoglobin levels. C. Creatinine levels. D. Platelet count.

A. Liver enzyme levels.

Patients who are in the initial period of treatment for tuberculosis need to be taught to perform which procedures? (Select all that apply) A. Wash their hands and cover their mouths when coughing or sneezing to reduce the spread of tuberculosis. B. Throw away dirty tissues in the proper receptacle. C. Be sure to get adequate rest, nutrition, and relaxation. D. Skip medication doses occasionally if gastric distress occurs. E. Avoid all visitors until symptoms improve.

A. Wash their hands and cover their mouths when coughing or sneezing to reduce the spread of tuberculosis. B. Throw away dirty tissues in the proper receptacle. C. Be sure to get adequate rest, nutrition, and relaxation.

Signs of liver dysfunction-

Abdominal pain, anorexia, nausea, vomiting. Malaise, fatigue. Jaundice, dark urine, increased liver enzymes.

Streptomycin

An aminoglycoside. Second-line antitubercular drug. Used in combination with other drugs because of the toxicity associated with aminoglycosides. *Adverse effects*- ototoxicity, nephrotoxicity, bone marrow depression.

During antitubercular therapy with isoniazid, a patient received another prescription for pyridoxine. Which statement by the nurse best explains the rationale for this second medication? A. "This vitamin will help to improve your energy levels." B. "This vitamin helps to prevent neurologic adverse effects." C. "This vitamin works to protect your heart from toxic effects." D. "This vitamin helps to reduce gastrointestinal adverse effects."

B. "This vitamin helps to prevent neurologic adverse effects."

The nurse is monitoring for liver toxicity in a patient who has been receiving long-term isoniazid therapy. Manifestations of liver toxicity include- (Select all that apply) A. Orange discoloration of sweat and tears. B. Darkened urine. C. Dizziness. D. Fatigue. E. Visual disturbances. F. Jaundice.

B. Darkened urine. D. Fatigue. F. Jaundice.

The nurse should include which information in the teaching plan for a patient who is taking isoniazid (INH)? A. Urine and saliva may be reddish-brown. B. Pyridoxine (vitamin B6) may be needed to prevent neurotoxicity. C. Injection sites should be rotated daily. D. The medication should be taken with an antacid to reduce gastric distress.

B. Pyridoxine (vitamin B6) may be needed to prevent neurotoxicity.

Why is tuberculosis difficult to treat?

Because it is a very slow-growing organism.

Rifampin (Rifadin)

Broad spectrum antibiotic: inhibits protein synthesis, inhibits RNA synthesis. Used for mycobacterium leprae (leprosy) and TB bovis. *Adverse side effects*- hepatotoxicity, N/V/A, flu-like symptoms (aches, malaise), discolors body fluids red. *Interactions*- enzyme inducer: accelerates metabolism of other drugs: decreases effectiveness: beta blockers, BCP, warfarin, oral antidiabetics, phenytoin, benzodiazepines. Use alternative form of birth control.

A patient newly diagnosed with tuberculosis asks the nurse how long he will need to take "all this medicine." The nurse replies that drug therapy for active tuberculosis may need to last how long? A. 6 months B. 12 months C. 24 months D. A lifetime

C. 24 months

The nurse would correctly identify the method of action of isoniazid (INH) as which of the following? A. Inhibiting protein synthesis. B. Inhibiting mycobacterial ATP synthase. C. Altering cell wall synthesis. D. Its method of action is unknown.

C. Altering cell wall synthesis.

The nurse is teaching a patient who is starting antitubercular therapy with rifampin. Which adverse effects would the nurse expect to see? A. Headache and neck pain. B. Gynecomastia. C. Reddish brown urine. D. Numbness or tingling of extremities.

C. Reddish brown urine.

When counseling a patient who has been newly diagnosed with TB, the nurse will make sure that the patient realizes that he or she is contagious- A. During all phases of the illness. B. Any time up to 18 months after therapy begins. C. During the postictal phase of TB. D. During the initial period of the illness and its diagnosis.

D. During the initial period of the illness and its diagnosis.

Nursing implications

Drug therapy can last 24 months. Consistent use is key, should be taken at the same time every day. Family members may need prophylactic treatment for up to a year. Take with food to decrease GI upset. Monitor signs of liver and kidney dysfunction. Avoid alcohol use (hard on liver + decreases effectiveness). Goals of therapy: reduce cough- decrease infectiousness. Effects will take at least 2 weeks after starting drug therapy. Evaluation of effectiveness: decreased cough, weight gain, increased energy. Final confirmation: sputum culture and chest x-ray.

Ethambutol (Myambutol)

First line treatment for tuberculosis. Suppresses RNA synthesis + inhibits protein synthesis. *Adverse effects*- retrobulbar neuritis, blindness, peripheral neuropathy, renal damage. *Contraindications*- optic neuritis, young children under the age of 13.

Isoniazid (INH)

Most widely used antitubercular drug. Disrupts cell wall synthesis by inhibiting mycolic acid, a component of the cell wall. Results in cell death. Used for prophylactic treatment of TB and treatment of active TB. Metabolized in the *liver*. *Adverse effects*- hepatotoxicity, peripheral neuropathy, eye infections, psych disturbances, hyperglycemia, depletion of vitamin B6 (Pyridoxine). Can cause false positive urine glucose tests.

Which two drugs cause red discoloration of body fluids?

Rifampin (Rifadin) Rifapentine (Priftin)

Diagnosis of TB

Step 1- Tuberculin skin test (Mantoux test). Step 2- If skin test results are positive, then chest x-ray. Step 3- If chest x-ray shows signs of tuberculosis, then culture of sputum or stomach secretions.

Pyrazinamide (PZA)

Used in combination with other antitubercular drugs. Bacteriostatic or bactericidal depending on the dose/concentration. Action is unknown. *Adverse effects*- hepatotoxicity, N/V/D, flu-like symptoms (aches, malaise), increased uric acid levels. *Interactions*- other TB drugs: increased hepatotoxicity.