Table 1.

Summary of data and results for nucleoside, nucleotide and non-nucleoside reverse transcriptase inhibitors and fusion inhibitor. (The intracellular half-life was used when it was known, since nucleoside intracellular half-lives differ greatly from the half-life in plasma. The decay rate d_R was calculated according to the formula d_R=24 log(2)/T_1/2, where T_1/2 is the half-life. The threshold levels for 10- and 50-fold resistance (R₂⁽¹⁰⁾ and R₂⁽⁵⁰⁾, respectively) were calculated using an antiviral effect limit of 1×10⁻³ (see figure 1). The penultimate column shows the number of doses that may be missed before 50-fold resistance emerges, assuming that the drug is able to control the mutant strain with perfect adherence. The final column shows the number of successive doses that must be taken after missing these doses, to be within a 1% tolerance of perfect adherence. In all cases, the numbers of missable and subsequent doses were estimated conservatively; for example, the missable dose threshold for Emtricitabine was 16.49 doses, while the subsequent dose threshold was 10.79, so this translates to 16 missable doses and 11 subsequent doses.)

drug	Ri (μM)	τ (days)	T1/2 (h)	R1 (μM)	$R_2^{(10)}$ (μM)	$R_2^{(50)}$ (μM)	missable	subsequent
Abacavir (ABC)	12	1/2	15	e−8	e−6	e−4	13	9
Didanosine (ddI)	4.65	1/2	25	e−5	e−3	e−1	11	14
Emtricitabine (FTC)	7.2	1	39	e−8	e−6	e−4	16	11
Lamivudine (3TC)	6	1/2	17	e−5	e−2	e−1	7	10
Stavudine (d4T)	2.144	1/2	7	e−6	e−4	e−2	2	4
Tenofivir (TDF)	1.184	1	17	e−5	e−3	e−2	1	4
Zalcitabine (ddC)	0.1008	1/3	3	e−8	e−6	e−4	1	1
Zidovudine (ZDV)	4.24	1/3	3	e−12	e−10	e−8	5	3
Delavirdine (DLV)	35	1/3	5.8	e−7	e−5	e−3	7	5
Efavirenz (EFV)	12.9	1	45	e−8	e−6	e−4	20	13
Nevirapine (NVP)	7.5	1/2	35	e−10	e−7	e−6	40	20
Enfuvirtide (T20)	18.36	1/2	3.8	e−9	e−7	e−5	3	3