Nucleoside Reverse Transcriptase Inhibitors (NRTI's)

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abacavir (Ziagen ®)	Atripla™ (Efavirenz, emtricitabine, and tenofovir)
Combivir ® (AZT 300mg+150 mg lamivudine)	didanosine (Videx ®)
emtricitabine (Emtriva ®)	Epzicom ® (abacavir 600mg + lamivudine 300mg)
lamivudine (Epivir ®)	stavudine (Zerit ® )
tenofovir (Viread ®)	Trizivir ® (abacavir 300mg + lamivudine 150mg + zidovudine 300mg)
Truvada ® (emtricitabine 200mg + tenofovir 300mg)	zalcitabine (Hivid ® )
zidovudine (Retrovir ® )

abacavir (Ziagen ®)

Dosing (Adults): The recommended oral dose of ZIAGEN for adults is 600 mg daily, administered as either 300 mg twice daily or 600 mg once daily, in combination with other antiretroviral agents. Warn about hypersensitivity reactions which can be lethal with rechallenge.

Dosage adjustment in hepatic impairment:
Mild dysfunction (Child-Pugh score 5-6): 200 mg twice daily (oral solution is recommended)
Moderate-to-severe dysfunction: Use is contraindicated by the manufacturer

SUPPLIED:
Solution, oral: 20 mg/mL (240 mL)
Tablet: 300 mg

Atripla™ (Efavirenz, emtricitabine, and tenofovir)

Dosing (Adults): Oral: One tablet once daily to be taken on an empty stomach (at bedtime is recommended).

Renal Dosing: — Moderate-to-severe renal impairment (CrCl <50 mL/minute): Use not recommended.

Admin: Should be taken on an empty stomach, normally at bedtime to increase gastrointestinal tolerance and
decrease nervous system manifestations.

Supplied: Tablet: Efavirenz 600 mg, emtricitabine 200 mg, and tenofovir disoproxil fumarate 300 mg.

Combivir ® (AZT 300mg+150 mg lamivudine):

Dosing (Adults): 1 tablet orally twice daily.

Supplied: coated tablet (zidovudine 300mg + lamivudine 150mg). Renal failure: Use each agent independently and adjust accordingly.

didanosine (Videx ®)

Dosing (Adults): Medication must be given on an empty stomach. In order to provide adequate buffering, patients must take at least 2 of the appropriate strength tablets at each dose when using either the once daily or twice daily regimens.

Patient weight <60 kg: (Tablets): 125 mg orally twice daily or 250mg once daily or 167 mg (Buffered powder) twice daily. Patient weight > 60kg: (Tablets): 200mg orally twice daily or 400mg orally once daily. (Buffered Powder): 250mg orally twice daily.

Supplied: chewable tablet: (25, 50, 100, 150, and 200mg); Oral powder for solution (100, 167, and 200mg packets).

Renal Dosing:

Patients > 60 kg
	Tablets	Powder
30-59	100 bid or 200mg qd	100 mg bid
10-29	150mg qd	167mg qd
<10	100mg qd	100mg qd
Patients < 60kg
	Tablets	Powder
30-59	75mg bid or 150mg qd	100mg bid
10-29	100 mg qd	100 mg qd
<10	75 mg qd	100mg qd

emtricitabine (Emtriva ®)

Mechanism of Action
Nucleoside reverse transcriptase inhibitor; emtricitabine is a cytosine analogue which is phosphorylated intracellularly to emtricitabine 5'-triphosphate which interferes with HIV viral RNA dependent DNA polymerase resulting in inhibition of viral replication.

Dosing (Adults): 200 mg orally once daily

Renal Dosing:
crcl 30-49 ml/min: 200 mg every 48 hours.
crcl 15-29 ml/min: 200 mg every 72 hours.
crcl <15 ml/min: 200 mg every 96 hours.

Supplied: Capsule: 200 mg

Epzicom ® (abacavir 600mg + lamivudine 300mg):

Mechanism of Action
Nucleoside reverse transcriptase inhibitor combination.
Abacavir is a guanosine analogue which is phosphorylated to carbovir triphosphate which interferes with HIV viral RNA-dependent DNA polymerase resulting in inhibition of viral replication.

Lamivudine is a cytosine analog. After lamivudine is triphosphorylated, the principle mode of action is inhibition of HIV reverse transcription via viral DNA chain termination; inhibits RNA-dependent DNA polymerase activities of reverse transcriptase.

Dosing (Adults): One tablet (abacavir 600 mg and lamivudine 300 mg) once daily.

Renal Dosing: crcl <50 ml/min: Use not recommended.
Hepatic Impairment: Use not recommended.

Supplied: Tablet: Abacavir 600 mg & lamivudine 300 mg

lamivudine (Epivir ®)

Lamivudine should not be co-administered with zalcitabine.
Mechanism of Action
Lamivudine is a cytosine analog. After lamivudine is triphosphorylated, the principle mode of action is inhibition of HIV reverse transcription via viral DNA chain termination; inhibits RNA- and DNA-dependent DNA polymerase activities of reverse transcriptase. The monophosphate form of lamivudine is incorporated into the viral DNA by hepatitis B virus polymerase, resulting in DNA chain termination.

INDICATIONS:
Epivir®: Treatment of HIV infection when antiretroviral therapy is warranted; should always be used as part of a multidrug regimen (at least three antiretroviral agents)

Epivir-HBV®: Treatment of chronic hepatitis B associated with evidence of hepatitis B viral replication and active liver inflammation

Dosing (Adults):
Note: The formulation and dosage of Epivir-HBV® are not appropriate for patients infected with both HBV and HIV. Use with at least two other antiretroviral agents when treating HIV

Prevention of HIV following needlesticks (unlabeled use): 150 mg twice daily (with zidovudine with or without a protease inhibitor, depending on risk)

HIV: 150 mg twice daily or 300 mg once daily; <50 kg: 2 mg/kg twice daily

Treatment of hepatitis B (Epivir-HBV®): 100 mg/day

Dosing interval in renal impairment in patients >16 years for HIV:
Clcr 30-49 mL/minute: Administer 150 mg once daily
Clcr 15-29 mL/minute: Administer 150 mg first dose, then 100 mg once daily
Clcr 5-14 mL/minute: Administer 150 mg first dose, then 50 mg once daily
Clcr<5 mL/minute: Administer 50 mg first dose, then 25 mg once daily

Dosing interval in renal impairment in adult patients with hepatitis B:
Clcr 30-49: Administer 100 mg first dose then 50 mg once daily
Clcr 15-29: Administer 100 mg first dose then 25 mg once daily
Clcr 5-14: Administer 35 mg first dose then 15 mg once daily
Clcr<5: Administer 35 mg first dose then 10 mg once daily

Dialysis: Negligible amounts are removed by 4-hour hemodialysis or peritoneal dialysis. Supplemental dosing is not required.

SUPPLIED:
Solution, oral:
Epivir®: 10 mg/mL (240 mL) [strawberry-banana flavor]
Epivir-HBV®: 5 mg/mL (240 mL) [strawberry-banana flavor]

Tablet:
Epivir®: 150 mg, 300 mg
Epivir-HBV®: 100 mg

stavudine (Zerit ® )

Dosing (Adults): Patient weight >60 kg: 40mg orally twice daily . Patient weight < 60kg: 30mg orally twice daily. Dosages may be decreased by 50% if peripheral neuropathy occurs. May be taken without regard to meals. Must decrease dose in renal dysfunction. Stavudine and Zidovudine should not be co-administered.

Supplied: [15, 20, 30, 40mg capsules; 1 mg/ml oral powder for solution].

Renal Dosing:

CRCL (ml/min)	WT > 60kg	WT <60kg
> 50	40mg q12h	30mg q12h
26-50	20mg q12h	15mg q12h
10-25	20mg q24h	15mg q24

tenofovir (Viread ®)

INDICATIONS:
Management of HIV infections in combination with at least two other antiretroviral agents

Mechanism of Action
Tenofovir disoproxil fumarate (TDF) is an analog of adenosine 5'-monophosphate; it interferes with the HIV viral RNA dependent DNA polymerase resulting in inhibition of viral replication. TDF is first converted intracellularly by hydrolysis to tenofovir and subsequently phosphorylated to the active tenofovir diphosphate; nucleotide reverse transcriptase inhibitor.

Dosing (Adults): 300 mg orally once daily with a meal.

Renal Dosing:
crcl 30-49 ml/min: 300 mg every 48 hours
crcl 10-29 ml/min: 300 mg twice weekly
crcl <10 ml/min: No recommendation available.
Hemodialysis: 300 mg every 7 days or after a total of 12 hours of dialysis (usually once weekly assuming 3 dialysis sessions lasting about 4 hours each).

Supplied: Tablet: 300 mg

Trizivir ® (abacavir 300mg + lamivudine 150mg + zidovudine 300mg)

Dosing (Adults): (>40 kg): 1 tablet twice daily; Note: Not recommended for patients <40 kg
Dosage adjustment in renal impairment: Because lamivudine and zidovudine require dosage adjustment in renal impairment, Trizivir® should not be used in patients with Clcr </= 50 mL/minute

Elderly: Use with caution

Supplied:
Tablet [film coated]: Abacavir 300 mg, lamivudine 150 mg, and zidovudine 300 mg

Truvada ® (emtricitabine 200mg + tenofovir 300mg):

Dosing (Adults): One tablet (emtricitabine 200 mg and tenofovir 300 mg) once daily.

Renal Dosing:
crcl 30-49 ml/min: 1 tab every 48 hours
crcl <30 ml/min: Not recommended.

Supplied:Tablet: Emtricitabine 200 mg and tenofovir 300mg.

zalcitabine (Hivid ® )

Dosing (Adults): 0.75 mg orally three times daily. Lamivudine should not be co-administered with zalcitabine.

Renal Dosing:
>40/ no change; 10-40/ 0.75 mg twice daily;
<10/ 0.75 mg once daily.

Supplied: [0.375mg , 0.75mg tablet]

zidovudine (Retrovir ® )

INDICATIONS:
Management of patients with HIV infections in combination with at least two other antiretroviral agents; for prevention of maternal/fetal HIV transmission as monotherapy

Dosing (Adults):
Prevention of maternal-fetal HIV transmission:
Maternal (may delay treatment until after 10-12 weeks gestation): Oral (per AIDSinfo 2003 guidelines): 200 mg 3 times/day or 300 mg twice daily until start of labor

During labor and delivery, administer zidovudine I.V. at 2 mg/kg over 1 hour followed by a continuous I.V. infusion of 1 mg/kg/hour until the umbilical cord is clamped

HIV infection: (ADULTS):
Oral: 300 mg twice daily or 200 mg 3 times/day

I.V.: 1-2 mg/kg/dose (infused over 1 hour) administered every 4 hours around-the-clock (6 doses/day)

Prevention of HIV following needlesticks (unlabeled use): 200 mg 3 times/day plus lamivudine 150 mg twice daily; a protease inhibitor (eg, indinavir) may be added for high risk exposures; begin therapy within 2 hours of exposure if possible

Patients should receive I.V. therapy only until oral therapy can be administered

Dosing interval in renal impairment: Clcr<10 mL/minute: May require minor dose adjustment

Hemodialysis: At least partially removed by hemo- and peritoneal dialysis; administer dose after hemodialysis or administer 100 mg supplemental dose; during CAPD, dose as for Clcr<10 mL/minute

Continuous arteriovenous or venovenous hemodiafiltration effects: Administer 100 mg every 8 hours

Dosing adjustment in hepatic impairment: Reduce dose by 50% or double dosing interval in patients with cirrhosis

Administration
Oral: Administer around-the-clock to promote less variation in peak and trough serum levels; may be administered without regard to food.
I.M.: Do not administer I.M.
I.V.: Avoid rapid infusion or bolus injection

Supplied:
Capsule: 100 mg
Injection, solution: 10 mg/mL (20 mL)
Syrup: 50 mg/5 mL (240 mL)
Tablet: 300 mg

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David F. McAuley, Pharm.D., R.Ph. GlobalRPh Inc.

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