What Is the Difference between Clonazepam and Lorazepam?

Clonazepam and lorazepam are both benzodiazepines, a class of medications used to treat generalized anxiety disorders, panic attacks, post-traumatic stress disorder (PTSD), alcohol withdrawal and insomnia due to their sedative effects. Benzodiazepines have been in use since the 1950s and are classified by their length of action: short to long-acting. They interact with the brain using the same chemical receptors as alcohol, hence their use in the medical treatment of alcohol withdrawal and their tendency to become addictive to those who use them regularly. In fact, benzodiazepines require a doctor's prescription in some countries because of their addictive qualities and their potential for misuse. Although they belong to the same family of drugs, clonazepam and lorazepam differ in their available forms, recommended dosages, recommended uses, absorption rates and other factors.

Different routes of administration are available for clonazepam and lorazepam. For example, lorazepam can be administered orally as tablets, sublingually (SL), intramuscularly (IM) or intravenously (IV) for faster onset of action. Clonazepam by comparison is only available for oral administration as tablets. Though both are benzodiazepines, the two drugs are in different classes. Clonazepam is considered a long-acting benzodiazepine, with a rapid onset time of one to four hours and a half-life of approximately 34 hours, while lorazepam is a short-acting benzodiazepine with the same approximate onset time but a half-life of only 15 hours.

The therapeutic uses of these medications are similar but differ in important ways. Although both are used to control anxiety and can be used as anticonvulsants, lorazepam is the preferred alcohol withdrawal agent of the two. Clonazepam, however, is the preferred agent to utilize for benzodiazepine withdrawal symptoms and dosage taper programs. It is also used to treat social phobias and pain of neurological origin. Intravenous lorazepam administered preoperatively is the expected drug of choice to allay surgery-related fears.

Clonazepam and lorazepam have similar side effects due to their identical method of action on the central nervous system. Drowsiness, low blood pressure, an unsteady gait, memory lapses, and difficulty with coordination can all result from taking a prescribed dose. Both drugs can be extremely dangerous respiratory depressants when combined with alcohol. Interactions with other drugs will also be very similar for both. Neither should ever be combined with pain medications, sleep medications or any type of sedating drug without the knowledge and permission of the attending physician.

Furthermore, both clonazepam and lorazepam will have the same withdrawal symptoms of increased anxiety, insomnia, panic attacks, rapid heart rate and other symptoms. Owing to clonazepam's longer half-life, however, the side effects will not occur until a longer length of time has passed since the last dose. It is strongly recommended by medical authorities that any discontinuation of benzodiazepines used regularly for as little as six weeks be undertaken only under the supervision of a physician. These medications are usually tapered during a withdrawal program as opposed to abrupt cessation.