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Viread

Clinical Pharmacology
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Clinical Pharmacology

Viread

Following multiple dosing to HIV-negative subjects receiving either chronic methadone maintenance therapy or oral contraceptives, or single doses of ribavirin, steady state tenofovir pharmacokinetics were similar to those observed in previous studies, indicating lack of clinically significant drug interactions between these agents and VIREAD.

Table 4 - Drug Interactions: Changes in Pharmacokinetic Parameters for Coadministered Drug in the Presence of VIREAD

Coadministered Drug Dose of
Coadministered Drug (mg)		 N % Change of Coadministered Drug Pharmacokinetic
Parameters1 (90% CI)
Cmax AUC Cmin
Abacavir 300 once 8 ↑12
( ↓1 to ↑26)		 ⇔ NA
Adefovir dipivoxil 10 once 22 ⇔ ⇔ NA
Atazanavir2 400 once daily × 14 days 34 ↓21
( ↓27 to ↓14)		 ↓25
( ↓30 to ↓19)		 ↓40
( ↓48 to ↓32)
Atazanavir2 Atazanavir/ Ritonavir 300/100 once daily × 42 days 10 ↓28
( ↓50 to ↑5)		 ↓253
( ↓42 to ↓3)		 ↓233
( ↓46 to ↑10)
Efavirenz 600 once daily × 14 days 30 ⇔ ⇔ ⇔
Emtricitabine 200 once daily × 7 days 17 ⇔ ⇔ ↑20
(↑12 to ↑29)
Indinavir 800 three times daily × 7 days 12 ↓11
( ↓30 to ↑12)		 ⇔ ⇔
Lamivudine 150 twice daily × 7 days 15 ↓24
( ↓34 to ↓12)		 ⇔ ⇔
Lopinavir Ritonavir Lopinavir/Ritonavir 400/100 twice daily × 14 days 24 ⇔ ⇔ ⇔
⇔ ⇔ ⇔
Methadone4 40–110 once daily × 14 days5 13 ⇔ ⇔ ⇔
Nelfinavir M8 metabolite 1250 twice daily × 14 days 29 ⇔ ⇔ ⇔
⇔ ⇔ ⇔
Oral Contraceptives6 Ethinyl Estradiol/ Norgestimate (Ortho-Tricyclen) once daily × 7 days 20 ⇔ ⇔ ⇔
Ribavirin 600 once 22 ⇔ ⇔ NA
Saquinavir Saquinavir/Ritonavir 1000/100 twice daily ×14 days 32 ↑22
( ↑6 to ↑41)		 ↑297
( ↑12 to ↑48)		 ↑477
(↑23 to ↑76)
Ritonavir ⇔ ⇔ ↑23
(↑3 to ↑46)
1.Increase = ↑; Decrease = ↓; No Effect = ⇔ ; NA = Not Applicable
2.Reyataz Prescribing Information
3.In HIV-infected patients, addition of tenofovir DF to atazanavir 300 mg plus ritonavir 100 mg, resulted in AUC and Cmin values of atazanavir that were 2.3- and 4-fold higher than the respective values observed for atazanavir 400 mg when given alone.
4.R-(active), S- and total methadone exposures were equivalent when dosed alone or with VIREAD.
5.Individual subjects were maintained on their stable methadone dose. No pharmacodynamic alterations (opiate toxicity or withdrawal signs or symptoms) were reported.
6.Ethinyl estradiol and 17-deacetyl norgestimate (pharmacologically active metabolite) exposures were equivalent when dosed alone or with VIREAD.
7.Increases in AUC and Cmin are not expected to be clinically relevant; hence no dose adjustments are required when tenofovir DF and ritonavir-boosted saquinavir are coadministered.

Table 5 - Drug Interactions: Pharmacokinetic Parameters for Didanosine in the Presence of VIREAD

Didanosine1
Dose (mg)/ Method of
Administration2		 VIREAD Method of
Administration2		 N % Difference (90% CI) vs. Didanosine 400 mg Alone, Fasted3
Cmax AUC
Buffered tablets
400 once daily4 × 7 days Fasted 1 hour after didanosine 14 ↑28
(↑11 to ↑48)		 ↑44
(↑31 to ↑59)
Enteric coated capsules
400 once, fasted With food, 2 hours after didanosine 26 ↑48
(↑25 to ↑76)		 ↑48
(↑31 to ↑67)
400 once, with food Simultaneously with didanosine 26 ↑64
(↑41 to ↑89)		 ↑60
(↑44 to ↑79)
250 once, fasted With food, 2 hours after didanosine 28 ↓10
(↓22 to ↑3)		 ⇔
250 once, fasted Simultaneously with didanosine 28 ⇔ ↑14 (0 to ↑31)
250 once, with food Simultaneously with didanosine 28 ↓29
(↓39 to ↓18)		 ↓11
(↓23 to ↑2)
1.See PRECAUTIONS regarding use of didanosine with VIREAD.
2.Administration with food was with a light meal (~373 kcal, 20% fat).
3.Increase = ↑; Decrease = ↓; No Effect = ⇔
4.Includes 4 subjects weighing < 60 kg receiving ddI 250 mg.

Description of Clinical Studies

Treatment-Naïve Patients

Study 903: VIREAD + Lamivudine +Efavirenz Compared to Stavudine + Lamivudine + Efavirenz
Brand Name: Viread
Generic Name: Tenofovir Disoproxil Fumarate
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