Stability of Drugs and Dosage Forms Sumie Yoshioka

2.2. • Factors Affecting Chemical Stability 63
Table 4. Activation Energy Values for Degradation of Representative Drug Substances
Drughydrolysis E a (kcal/mol) PH a Reference
Hydrolysis
Ampicillin 9.2 b 9.78 65
18.3 b 4.93 65
Cefotaxime 9.4 8.94 73
24.7 5.52 73
Echothiophateiodide 10 OH – 49
23 H + 49
Indomethacin 10.1 11 58
Methylphenidate 12.35 OH – 19
15.98 H + 19
Oxazolam 12.4 8.0 93
Succinylcholine chloride 13.09 OH – 32
17.23 H + 32
Haloxazolam 15.2 1.3 94
Mitomycin C 16.2 b,c 5.20 105
Procaine 16.8 H + 10
Hydrocortisone sodium phosphate 17.0 H + 47
Diazepam 17.2 10.18 87
Atropine 17.2 H + 16
20.9 H + 26
Acetaminophen 17.42 6 53
Phenethicillin 17.6 6.7 68
Amobarbital 18.6b 10.12 80
Benzocaine 18.6 H + 10
Ethylparaben 18.7 9.16 22
Meperidine 18.77 6 28
Nitrofurantoin 18.9 H + 109
Rifampicin 19.2 H + 111
Oxazepam 20.0 3.24 87
26.1 8.52 87
Benzylpenicillin 20.3 2.7 64
Thiamine hydrochloride 21 9.90 102
29 1.70 102
Cefadroxil 21.4 7.00 71
Carmethizole 21.5 9.90 44
Chlorphenesin carbamate 21.8 H+ 43
Cephalothin 22.6 5.00 70
28.5 10.00 70
Sulfacetamide 22.9 d 7.40 60
Carbenicillin 23.4 4.45 67
27.45 10.47 67
Furosemide 23.5 H + 100
Chloramphenicol 24.0 6.00 15
Chlorambucil 24.4 e 7.00 120
Pilocarpine 25.02 OH – 37
Cocaine 26.2 6.25 34
Moricizine 27.5 6.0 61
Clindamycin 38.0 1.10 123
(continued)