| Barbiturate
structure-activity relationship |
| Group |
Position R1 |
Position R2 |
Characteristics |
| Oxybarbiturates |
H |
O |
Delay in onset
of action, hypnotic property depends on side chains at C5, prolonged duration of action |
| Methylated
Barbiturates |
CH3 |
O |
Usually rapid
onset of action, rapid recovery, high incidence of excitatory phenomena |
| Thiobarbiturates |
H |
S |
Rapid smooth
onset of action, rapid recovery |
| Methylated
thiobarbiturates |
CH3 |
S |
Rapid onset of
action, high incidence of excitatory phenomena precludes clinical use |
|
|