Parallel design

Appropriate study design should be selected to achieve the desired outcome. A description of the type/design of frial to be conducted (e.g., double-blind, placebo-controlled, parallel design) and a schematic diagram of trial design. 

In those instances when the cross-over design is not possible, a parallel design may be required. In such a protocol the test subjects are divided into... 

The ability of a tPLC system to produce the same values of retention time and peak areas for analytes of interest is determined by evaluating the precision obtained under standardized conditions and analytical methods. The precision (reproducibility) values obtained are functions of the autosampler, cartridge, and detectors employed. Due to the parallel design of the tPLC system described in this chapter, reproducibility evaluations of retention time and peak area involved comparisons of results obtained for these parameters for consecutive runs performed in the same column and across different columns. 

Hagen NA, Souich P, Lapointe B, Ong-Lam M, Dubuc B, Walde D, Love R, Ngoc AH. (2008) Tetrodotoxin for moderate to severe cancer pain A randomized, double blind, parallel design multicenter study. J Pain Symptom Manage 35 420 29. 

Table 6.2 Comparison of crossover and parallel designs in cUnical studies ...

Connors, 1975 MPH 59 (59) 4-5 11 Minimal brain dysfunction Parallel design MPH 11.8 mg/day (MPH 1.5 mg/kg/d) 42 days 27/29 children improved Minimal SEs with a ttend towatd elevated blood ptessute... 

CBZ s spectrum of efficacy appears similar to that of lithium however, as noted earlier, it may be superior to lithium in mixed or dysphoric mania, rapid cyclers, and more severe episodes (e.g., fulminant, aggressive, psychotic) (202). The number of patients treated with CBZ for acute mania in some form of placebo-control design is very limited. In fact, we are not aware of any double-blind, placebo-controlled, parallel design studies addressing this question (i.e., class I design). 

As noted earlier, in the only double-blind, placebo-controlled, parallel design study of clonidine, Janicak et al. ( 264) studied a group of acutely ill, hospitalized manic patients, many with associated psychotic features. After a washout period averaging 1 week, patients were randomly assigned to receive either clonidine or placebo for a 2-week trial. The intent was to ascertain whether clonidine alone had any inherent antimanic properties, and therefore, no other concomitant psychotropics were allowed. Unfortunately, improvement in either group was minimal and did not differ, with some patients on clonidine developing problems with rash and hypotension. Doses of clonidine were comparable with those reported in prior positive studies, averaging 0.5 mg/day. 

As an example, consider H2. The nuclear spin of H is and we have three symmetric nuclear spin functions and one antisymmetric function. The symmetric spin functions are of the form (1.251)—(1.253), and correspond to the two nuclear spins being parallel. Designating the quantum number of the vector sum of the two nuclear spins as 7, we have 7= 1 for the symmetric spin functions. The antisymmetric spin function has the form (1.254), and corresponds to 7 0. The ground electronic state of H2 is a 2 state, and the nuclei are fermions hence the symmetric (7=1) nuclear spin functions go with the J= 1,3,5,... rotational levels, whereas the 7=0 spin function goes with the7=0,2,4,... levels. 

In case of two study medications, a sound alternative to a parallel design would be the (complete) cross-over study design. 

In a placebo-controlled, parallel-design, double-blind study in 24 male volunteers, amisulpride 100 mg bd for 7 days did not alter lithium pharmacokinetics (623). 

A within-subject, double-bhnd, placebo-controlled, parallel design has been used to measure the effects of citalo-pram (20 mg/day) and fluoxetine (20 mg/day) on the pharmacokinetics and pharmacodynamics of alprazolam (1 mg/day) (45). Fluoxetine significantly impaired the metabolism of a single oral dose of alprazolam 1 mg, leading to prolongation of the half-life and an increased AUC, whereas citalopram did not. Neither SSRI significantly affected the pharmacodynamic effects of alprazolam. This experiment suggests differential effects of citalopram and fluoxetine on alprazolam kinetics. 

A large, multicenter, double-blind, randomized, placebo-controUed, parallel-design study showed oral valacyclovir and oral acyclovir equally effective in the self-initiated treatment of recurrent genital herpes infection (Valaciclovir International Study Group). 

A multicenter, randomized, double-blind, double-placebo, parallel-design study of immunocompetent patients with recurrent HSV genital infections showed no significant difference between oral famciclovir and oral acyclovir in time to complete healing, resolution of symptoms, or frequency, type, and severity of adverse events (Chosidow et al.). 

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