| Formulation | Time to peak serum concentration | Comments |
| Theo-24 | Variable depending on whether taken in the morning after an overnight fast, after breakfast, or in the evening. | Incomplete absorption occurs when taken after an overnight fast; pH-dependent dissolution causes much more rapid (ie, dose-dumping) and complete absorption when taken after food or in the evening. |
| Generic SR tablets | 3 to 7 hours after morning dose when given every 12 hours. | Scored tablets can be split without affecting absorption characteristics; complete absorption occurs in the presence or absence of food. |
| Generic SR capsules | 3 to 7 hours after morning dose when given every 12 hours. | Can be opened and sprinkled on a spoonful of soft food for children who cannot swallow the capsule; contents must be swallowed without chewing; complete absorption occurs in the presence or absence of food. |
| Uniphyl | 8 to 12 hours after once-daily evening dose. | Incomplete absorption occurs when taken after overnight fast; more complete absorption occurs when taken after food or in the evening. |
