Physical Dependence - Rebound Syndrome

Rebound Syndrome

A wide range of drugs whilst not causing a true physical dependence can still cause withdrawal symptoms or rebound effects during dosage reduction or especially abrupt or rapid withdrawal. These can include caffeine, stimulants, steroidal drugs and antiparkinsonian drugs. It is debated if the entire antipsychotic drug class causes true physical dependency, if only a subset do, or if none do, but all, if discontinued too rapidly, cause an acute withdrawal syndrome. Drugs like cocaine, marijuana, amphetamines, and hallucinogens can be associated with minimal physical dependence but can still cause withdrawal or rebound symptoms. However, with sustained and heavy cocaine abuse signs of physiological dependence may occur. When talking about illicit drugs rebound withdrawal is, especially with stimulants, sometimes referred to as "coming down" or "crashing".

Some drugs, like anticonvulsants and antidepressants, describe the drug category and not the mechanism. The individual agents and drug classes in the anticonvulsant drug category act at many different receptors and it is not possible to generalize their potential for physical dependence or incidence or severity of rebound syndrome as a group so need to be looked at individually. Anticonvulsants as a group however are known to cause tolerance to the anti-seizure effect. SSRI drugs, which have an important use as antidepressants, are considered to cause physical dependence, although it is considered mild compared to drugs like opioids and GABA modulators, but they engender a discontinuation syndrome, which was originally called "SSRI withdrawal" until a 1997 symposium sponsored by Pfizer and Eli Lilly (the producers of several anti-depressants including Prozac and Effexor) was held, with the drug representative attendees concluding that "discontinuation syndrome" sounded less threatening than "withdrawal"; however, "SSRI discontinuation syndrome" is a withdrawal syndrome upon discontinuation of SSRI/SNRI drugs, just as "heroin discontinuation syndrome" is a synonym for "heroin withdrawal". Due to this, in Europe these drugs cannot be advertised as "non-habit forming". There have been case reports of dependence with venlafaxine (Effexor).