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New drugs
(Aust Prescr 1999;22:125-7)
Some of the views expressed in the following notes on newly approved products should be regarded as tentative, as there may have been limited published data and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. As a result of fuller experience, initial comments may need to be modified. The Committee is prepared to do this. Before new drugs are prescribed, the Committee believes it is important that full information is obtained either from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Ziagen (Glaxo Wellcome)
300 mg tablets
20 mg/mL oral solution
Approved indication: HIV infection
Australian Medicines Handbook Section 5.3.3
Reverse transcriptase inhibitors can be used in combination with other drugs for the treatment of HIV infection. Abacavir is a nucleoside reverse transcriptase inhibitor which can be used in combination with drugs such as zidovudine and lamivudine.
The drug is taken twice a day. It is well absorbed with a bioavailability of 83%. Abacavir penetrates the cerebrospinal fluid. It is almost completely metabolised by the liver, with most of the metabolites being excreted in the urine.
The major trial of abacavir in untreated adults compared the combination of zidovudine, lamivudine and abacavir with zidovudine and lamivudine. As the double-blind stage of the trial lasted for only 16 weeks surrogate end-points were used. After one month of treatment, the proportion of patients with low plasma concentrations of HIV increased in the patients given triple therapy. At week 16, significantly more of the patients given abacavir had undetectable concentrations of HIV RNA. The CD4 cell count increased, but there was no significant difference between the rises in each group.
A similar study in previously treated children found that the advantage of abacavir was less clear. There are few data on the use of abacavir by previously treated adults.
Approximately 3% of patients will develop a potentially fatal hypersensitivity reaction. This usually occurs in the first six weeks of therapy and commonly presents with fever and rash. Patients may also complain of vomiting, diarrhoea and itching. The drug should be stopped immediately and never restarted as this may kill the patient.
Most patients with HIV infection taking a combination of drugs will develop adverse effects. Common complaints are nausea, headache and fatigue.
While the Australian Drug Evaluation Committee has approved abacavir for use in Australia, the role of the drug in therapy, particularly for previously treated patients, will require more study.
Raxar (Glaxo Wellcome)
600 mg tablets
Approved indication: specified infections
Australian Medicines Handbook Section 5.1.12
Grepafloxacin is a broad spectrum fluoroquinolone antibiotic. It has been approved for use in uncomplicated gonorrhoea, urethritis and cervicitis caused by Chlamydia trachomatis, acute bacterial exacerbations of chronic bronchitis and community-acquired pneumonia.
The dose of grepafloxacin depends on the condition being treated. Uncomplicated gonorrhoea can be treated with a single dose, while patients with chest infections can be treated for up to 10 days.
The absorption of the daily dose is not affected by food. The average plasma elimination half-life is 12 hours with most of the drug being cleared by the liver. Only 5-14% is excreted unchanged in the urine. Moderate or severe liver impairment is therefore a contraindication to grepafloxacin. As the metabolism of grepafloxacin involves cytochrome P450 (CYP1A2), there is a potential for interaction with drugs such as theophylline and caffeine.
The most common adverse reactions are nausea, altered taste, headache and dizziness. Grepafloxacin is a weak photosensitiser; this may be relevant in the Australian climate. As grepafloxacin can prolong the QT interval, it must not be given to patients who are taking medications which have a similar cardiac effect e.g. terfenadine, tricyclic antidepressants and some antipsychotics.
As there is concern about the development of antibiotic resistance, the fluoroquinolones should be used sparingly. Although studies have found grepafloxacin to have efficacy in its approved indications, it would not be the first-choice treatment. For example, the Antibiotic Guidelines1 recommend amoxycillin or doxycycline if treatment is needed for an exacerbation of chronic bronchitis. Prescribing a fluoroquinolone for such a common clinical condition risks increasing the problems of antibiotic resistance.
R E F E R E N C E
1. Writing Group for Therapeutic Guidelines: Antibiotic. Therapeutic guidelines:antibiotic. 10th ed. Melbourne: Therapeutic Guidelines Limited; 1998.
Synagis (Abbott)
vials containing 100 mg as powder for reconstitution
Approved indication: prevention of viral infection
Australian Medicines Handbook Section 5.3.2
The respiratory syncitial virus (RSV) commonly infects children. Usually only an upper respiratory tract infection develops, but some children can become seriously ill. The children at risk include those with congenital heart disease, chronic lung disease and premature babies. Palivizumab has been developed as one approach to preventing serious infections in high-risk infants.
The product is a recombinant monoclonal antibody directed against a protein in the RSV. It is injected intramuscularly once a month during the months that RSV is prevalent.
In a double-blind trial, 1002 children were randomised to receive palivizumab and 500 were injected with a placebo. More than 90% of each group received five injections. Approximately 11% of the children in the placebo group were admitted to hospital because of infection with RSV. Only 5% of the palivizumab group needed admission. The largest relative reduction (78%) was in the premature babies; approximately 8% of those given a placebo were admitted compared to 2% of those given palivizumab.1
The incidence of adverse effects in the clinical trial was similar for palivizumab and placebo. There was a slightly higher incidence of injection site reactions and altered liver function with palivizumab.1
No interaction studies have been done, but palivizumab is not expected to interfere with immunisations.
Overseas information suggests that one vial may cost nearly $2000. While this implies that palivizumab should only be used for patients with a very high risk of infection, children with severe bronchopulmonary dysplasia get the least benefit.
R E F E R E N C E
1. The IMpact-RSV Study Group. Palivizumab, a humanized respiratory syncytial virus monoclonal antibody, reduces hospitalization from respiratory syncytial virus infection in high-risk infants. Pediatrics 1998;102:531-7.
NEW FORMULATIONS
Persantin SR (Boehringer Ingelheim)
200 mg sustained-release capsules
Eprex (Janssen-Cilag)
vials of 1000 IU/0.5 mL, 2000 IU/mL, 4000 IU/mL and 10 000 IU/mL
pre-filled syringes of 1000 IU/0.5 mL, 2000 IU/0.5 mL, 3000 IU/0.3 mL, 4000 IU/0.4 mL and 10 000 IU/mL
Flixotide nebules (Glaxo Wellcome)
0.5 mg/2 mL and 2 mg/2 mL ampoules
Natrilix SR (Servier)
1.5 mg sustained-release tablets
Nasonex (Essex Pharma)
50 microgram/actuation aqueous nasal spray
OxyContin (Mundipharma)
10 mg, 20 mg, 40 mg and 80 mg controlled-release tablets
NEW STRENGTHS
Zeffix (Glaxo Wellcome)
100 mg tablets
Fraxiparin Forte (Sanofi Winthrop)
19 000 IU aXa/mL injection
NEW PROPRIETARY BRANDS
Aciclovir Intravenous Infusion (Pharmacia & Upjohn)
250 mg in 10 mL ampoules and 500 mg in 20 mL ampoules
Amohexal (Hexal)
250 mg and 500 mg tablets, 125 mg/5 mL and 250 mg/5 mL syrup
Diclosig (Sigma)
250 mg and 500 mg capsules
Doxyhexal (Hexal)
50 mg tablets
