Читать книгу The Dentist's Drug and Prescription Guide - Mea A. Weinberg - Страница 31

1 Q. What are the different types of chronic kidney disease?

2 A. Renal insufficiency, which is seen in the early phase, renal failure, which occurs when the kidneys cannot function in excretion, and end‐stage renal disease (ESRD) with the nephrons losing function and uremia, which leads to malnutrition, altered drug metabolism, electrolyte imbalance, bleeding, anemia, and death.

3 Q. Does renal disease alter the response to drugs?

4 A. Yes. The use of drugs in patients with reduced kidney function (e.g., patients on dialysis) may produce toxicity because of impaired elimination from the body. Whether the dose must be reduced depends on if the drug is eliminated entirely by renal excretion or is partly metabolized. Because the kidney is the major regulator of the internal fluid environment, the physiological changes associated with renal disease have pronounced effects on the pharmacology of many drugs.Either the dose does not have to be altered or the dosing interval is increased, or the dose is reduced while maintaining the same dosing interval (this is called dose reduction and is the preferred method because it maintains more constant plasma concentrations).

5 Q. What happens to the half‐life of the drug in kidney disease?

6 A. As the plasma half‐life of drugs excreted by the kidney is prolonged in renal failure, it may take many days for the reduced dosage to achieve a therapeutic plasma concentration. Therefore, the loading dose should usually be the same size as the initial dose for a patient with normal renal function, but the maintenance dose should be reduced. Consult with the patient's physician.

7 Q. What blood values must be known before prescribing for a patient with renal impairment?

8 A. Dose recommendations are based on the severity of renal impairment which is expressed in terms of glomerular filtration rate (GFR), measured by the creatinine clearance (CrCl). CrCl, which is measured as mL/min, indicates the function of the kidneys with regard to removing creatinine, a waste product, from the blood into the urine. Both blood and urine are required to determine CrCl. CrCl is not recommended for routine evaluation of kidney function. Normal CrCl is 80–120 mL/minute.Glomerular filtration rate indicates how efficiently the kidneys are filtering wastes from the blood. GFR is used to determine the severity of kidney disease. Chronic kidney disease is defined as GFR <60 mL/min/1.73 m2 or GFR ≥60 mL/min/1.73 m2 together with kidney damage for more than three months. Serum creatinine levels are used to measure GFR (Brockmann 2010; Hassan et al. 2009).

9 Q. When should antibiotics be given to a patient undergoing dialysis?

10 A. Antibiotics should be administered after dialysis to allow for therapeutic concentrations to be maintained.

11 Q. What is the severity scale for renal disease?

12 A. Currently, according to the National Kidney Foundation, there is no uniform classification of the stages of chronic kidney disease (Table 3.18). A review of textbooks and journal articles clearly demonstrates ambiguity and overlap in the meaning of current terms.

13 Q. Can penicillin V be prescribed to patients with renal impairment?

14 A. Penicillin V is rapidly excreted through the kidneys in the urine. There is a delay in excretion in patients with impaired renal function. When GFR is <10 mL/min/1.73 m2 then the dose of penicillin V should be reduced to 250 mg every six hours.

15 Q. Which antibiotics do not require a change in dosing adjustment in chronic kidney disease?

16 A. Azithromycin, clindamycin, doxycycline (www.remedirx.com/wp‐content/uploads/2016/01/2016‐01‐M.R.‐Antibiotic‐Renal‐Dosing.pdf)

17 Q. Why is it important to know about bleeding problems in renal disease patients?

18 A. There may be a prolonged bleeding time (altered platelet aggregation) due to uremia (syndrome associated with fluid, electrolyte, and hormone imbalances and metabolic abnormalities). The platelet and hematocrit levels should be known especially if bleeding during dental treatment is anticipated. Thus, a consultation with the patient's nephrologist is required before any type of dental surgery.

19 Q. If a patient with a kidney transplant requires antibiotic prophylaxis, which antibiotic is recommended?

20 A. For antibiotic prophylaxis, no dosing adjustments are required for azithromycin or clindamycin. Amoxicillin requires dosage adjustments. If the patient is taking cyclosporine after the kidney transplant, then clarithromycin and erythromycin should not be prescribed due to the risk of cyclosporine toxicity.

21 Q. Should fluoride topical products such as PreviDent® be prescribed to a patient with renal disease?

22 A. No. PreviDent contains 1.1% sodium fluoride, which is indicated for the prevention of tooth decay, reducing dentinal hypersensitivity and remineralization. Topical fluoride should never be swallowed; it is toxic. Topical fluorides should not be prescribed to a patient with kidney disease because fluoride is highly excreted by the kidneys so the risk of toxicity is greater in patients with impaired kidney function.

23 Q. What are the treatments for renal disease?

24 A. Treatments for renal disease include monitoring with diet control, hemodialysis or kidney transplant. Most patients undergo hemodialysis rather than peritoneal dialysis.

25 Q. How often does a patient usually have hemodialysis?

26 A. Every 2–3 days for 3–5 hours.

27 Q. How soon after a patient undergoes hemodialysis should they have dental procedures?

28 A. A consultation with the patient's nephrologist is necessary. Because of the increased risk of bleeding, it is best to see the patient on days when they are not undergoing dialysis. Heparin, an anticoagulant, is injected into the patient before dialysis to facilitate blood cycling through the dialyzer. If heparin has a half‐life of four hours, then it takes about five half‐lives to be completely eliminated from the body, about 20 hours. It is best to treat the patient one day after hemodialysis.

29 Q. Is antibiotic prophylaxis required for a patient having hemodialysis?

30 A. It is suggested to have a consultation with the nephrologist regarding this because there are many medical conditions that may require antibiotic prophylaxis. During hemodialysis, a surgically produced arteriovenous fistula is made, which may be susceptible to infection.

31 Q. How do I prescribe medications for a patient with kidney disease?

32 A.Inappropriate dosing in patients with chronic kidney disease can cause toxicity or ineffective therapy. Dosages of drugs cleared renally are based on renal function (calculated as GFR or CrCl). Dosing guidelines are divided into three broad GFR categories:<10 mL/min/1.73 m210–50 mL/min/1.73 m250 mL/min/1.73 m2It is advisable to contact the patient's physician and a pharmacist when prescribing medications. The type and severity of renal impairment must be determined. It is most important to obtain a copy of the patient's blood test to determine the GFR, which is the most reliable value for overall kidney function.

33 Q. Can local anesthetics be administered to patients with chronic kidney disease?

34 A. All amide local anesthetics including lidocaine and all other injectable anesthetics are metabolized by the liver. No adjustments are needed.

35 Q. Are most antibiotics safe to prescribe in renal disease?

36 A. See Table 3.18. Many antibiotics can induce renal dysfunction. Acute tubular necrosis (ATN) and interstitial nephritis are the most common types of acute renal failure associated with antibiotic use. Acute interstitial nephritis may occur within minutes of drug exposure or may not develop for several months. Preexisting renal disease, dose, duration, and prior exposure to the offending antibiotic may increase the susceptibility of patients to acute interstitial nephritis. Some antibiotics that can cause this adverse effect include penicillin, amoxicillin, and fluoroquinolones. Tetracycline is contraindicated in patients with renal disease and may cause renal failure because it is 50–60% eliminated through the kidneys (Miller and McGarity 2009). Azithromycin, clindamycin, and doxycycline do not require a dosage or interval change and are safe to use. Doxycycline is only 20–30% eliminated through the kidneys, so no dosage adjustment is needed.

Table 3.18 Severity scale for renal disease

Source: Adapted from National Kidney Foundation (https://renal.org/information‐resources/the‐uk‐eckd‐guide/ckd‐stages).

Grade (severity)	Glomerular filtration rate (GFR)	Creatinine clearance (CrCl)
Mild	20–50 mL/min/1.73 m2	1.7–3.4 mg/dL
Moderate	10–20 mL/min/1.73 m2	3.4–7.9 mg/dL
Severe	<10 mL/min/1.73 m2	>7.9 mg/dL
Stage	Severity	GFR
Stage 1	Normal or increased GFR	≥90 mL/min/1.73 m2
Stage 2	Mild	60–89 mL/min/1.73 m2
Stage 3	Moderate	30–59 mL/min/1.73 m2
Stage 4	Severe	15–29 mL/min/1.73 m2
Stage 5	Kidney failure	<15 mL/min/1.73 m2