T-20 (enfuvirtide, Fuzeon) cannot be taken by mouth because it is broken down by the digestive system. However, when administered by injection under the skin, T-20 achieves sufficient levels in the blood to have anti-HIV activity.

The recommended adult dosage is 90mg injected twice daily. Once-daily dosing at a dose of 180mg has been examined in a clinical trial. Although this dose led to similar levels of T-20 exposure and rates of side-effects, the study suggested that once-daily dosing might be less effective in reducing viral loads^[1]. Larger and longer-term studies are needed to confirm this finding.

T-20 is not an easy option because injections have to be prepared each day. Patients are provided with a carton containing phials of T-20 powder, phials of water used to dissolve the powder, as well as syringes and alcohol swabs. Detailed, step-by-step instructions on how to inject T-20 are included in the carton.

The drug has to be reconstituted from a powder, in a five-step process:

1. Users must use a disposable syringe to draw up sterile water from the phial.
2. The sterile water is then injected slowly into another phial containing the freeze-dried powder.
3. The phial is rocked slowly from side to side in order to dissolve the powder and then left for up to 45 minutes.
4. When the powder has dissolved, the phial’s lid must be pierced with a second sterile needle and the liquid drawn up into the syringe.
5. The liquid is then injected beneath the skin of the abdomen, the arm or the leg.

A phial of dissolved powder can be prepared at the beginning of the day for use in the evening, or in the evening for use the following morning. It should be kept in the refrigerator until it is used. Although the drug should be taken every twelve hours, pharmacokinetic studies suggest that a delay of up to four hours is unlikely to be too serious.

Despite concerns that the process of preparation and self-injection may be too difficult for many people, a survey of 638 people who were taking T-20 provides evidence that most people can manage the process: 67% found self-injection easy or very easy and only 11% found it difficult or very difficult^[2]. Around 13% found dissolving medication difficult or very difficult but only 1% reported difficulty disposing of needles and phials. Another assessment of patient satisfaction with self-injected therapy was encouraging, with only 13% of participants reporting difficulties^[3].

A needle-free method of delivering T-20 is available to some patients in the United States, but not in Europe. The Biojector 2000 system is a carbon dioxide-powered system that delivers drugs through the skin. It results in improved dispersion of T-20, with more consistent depth of delivery and a wider choice of injection sites, resulting in improved patient satisfaction over injection. One study has shown that the needle-free method results in similar drug levels to injection but with less severe injection site reactions^[4]. However, three cases of transient nerve pain have been reported in patients using this system. This is believed to be due to low fat levels under the skin in these patients, and injection near the joints, where the nerves are closer to the surface of the skin^[5].

The United States Food and Drug Administration is currently considering including information on the Biojector 2000 system in its printed information on T-20. Once this has taken place, Roche hopes to facilitate access to this system in Europe.