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I heard of a new injectable form of medication for alcoholism. What is it, and what are its advantages?

The FDA has recently approved an injectable form of naltrexone (known by its trade name as Vivitrol) that is a long-acting form of the drug and therefore requires only monthly injections. The purpose of the monthly injection is to enhance medication adherence, which is the biggest stumbling block for many patients struggling with mental illnesses. The approval, based on a study published in the Journal of the American Medical Association in April 2005, demonstrated that Vivitrol resulted in a 25% decrease in the event rate of heavy drinking days. A heavy drinking day is defined as equal to or greater than five standard drinks a day for men and four standard drinks a day for women. The event rate of heavy drinking is defined as the number of heavy drinking days divided by the number of days at risk for heavy drinking. The injections were well tolerated, with few adverse events and no evidence of liver disease, which had previously been a concern regarding this medication. Not surprisingly, the average decrease in heavy drinking days was greatest in those individuals who drank the most during the study. (The more one drinks, the greater opportunity there is to cut down.) The placebo group also received therapy in addition to sham injections. This group also demonstrated improvement in event rate of heavy drinking days but not to the same degree as those on the injectable naltrexone. The general conclusion was that injectable naltrexone offers a very important alternative to oral naltrexone by increasing adherence and therefore improving outcomes. Table 11 provides a summary of naltrexone.

Vivitrol an injectable, long acting form of naltrexone.

How is acamprosate different from other medications?

Acamprosate (Campral) is the third and final medication approved for the treatment of alcoholism. Its mechanism of action is unknown, although it is referred to as a glutamate receptor blocker. As you may recall from Question 6, glutamate is the major excitatory neurotransmitter in the brain. It is believed that chronic alcohol ingestion adds to the effects of the major inhibitory neurotransmitter, GABA. In order to compensate for this, the brain decreases GABA effectiveness and improves the effectiveness of glutamate in order to achieve a balance. When alcohol is suddenly removed from the rebalanced system, GABA is now left in a deficient state while glutamate is overactive. This is believed to cause many of the craving and withdrawal symptoms that people experience with alcohol dependency. It is thought that acamprosate enhances GABA transmission and inhibits glutamate transmission in order to restore the brain to its previous uncompensated state.

Unlike naltrexone, which focuses on reducing problem drinking, acamprosate targets abstinence. Acamprosate has been studied thoroughly in Europe, and very good results were demonstrated with 1-year abstinence rates of 18% compared with placebo-controlled abstinence rates of only 7%. At 2 years, the acamprosate groups abstinence rates fell to 12%, whereas the placebo group's abstinence rates fell to 5%. Some preliminary studies have suggested that using acamprosate in conjunction with naltrexone is better than using either alone. Acamprosate is well tolerated and can be prescribed for even patients with liver disease. Diarrhea, which eventually improves with time, is the most common side effect.

An intriguing use of acamprosate has been proposed based on a study conducted in 2001. Animals that were experiencing alcohol withdrawal symptoms were given the medication. It was shown to reduce glutamate's excitatory effects, thus possibly providing a neuroprotective effect and reducing the impact of withdrawal on the brain. Thus, the potential of using this medication as an adjunct to detoxification remains an open question; however, it would be an off-label treatment (see Questions 52 and 53 for other medications that are prescribed off-label). For further information regarding the reasons for detoxification and the medications necessary to manage detox effectively, please see Questions 55 and 56 and Table 12.

Neuroprotective a protection of the nervous system against toxic substances.

Off-label prescribing of a medication for indications other than those outlined by the Food and Drug Administration.

Table 12 Acamprosate (Campral): A Drug to Maintain Alcohol Abstinence

Drug Name

Acamprosate (Campral) — Synthetic compound with a chemical structure similar to that of the endogenous amino acid homotaurine (structural analogue of GABA). Mechanism of action to maintain alcohol abstinence not completely understood. Hypothesized to interact with glutamate and GABA neurotransmitters centrally to restore neuronal excitation and inhibition balance. Not associated with tolerance or dependence development. Use does not eliminate or diminish alcohol withdrawal symptoms. Indicated to maintain alcohol abstinence as part of a comprehensive management program that includes psychosocial support. Available as a 333-mg tablet.

Adult Dose

666 mg PO tid; initiate as soon as possible after alcohol withdrawal when abstinence has been achieved; if < 60 kg, may need to decrease dose by 333 — 666 mg/day.

CrCl 30 — 50 mL/min: 333 mg PO tid

Pediatric Dose

Not established


Documented hypersensitivity, severe renal impairment (i.e., CrCl < 30 mL/min)


Coadministration with naltrexone increases acamprosate Cmax and AUC, but no dose adjustment necessary


C — Safety during pregnancy has not been established.


Diarrhea is most common adverse effect (20%), but dropouts are few, additional common adverse effects are dizziness, itching, nausea, flatulence, headache, and increased sexual desire; depression and anxiety incidence slightly higher than that of placebo in one study.

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