(Aust Prescr 1999;22:75-7)
Letters, which may not necessarily be published in full, should be restricted to not more than 250 words. When relevant, comment on the letter is sought from the author. Due to production schedules, it is normally not possible to publish letters received in response to material appearing in a particular issue earlier than the second or third subsequent issue.
Topical retinoids and photosensitivity
Editor, – I would be interested to know if you have data on the use of tretinoin and alpha-hydroxy acid creams regarding their potential for preventing or aggravating solar skin damage and the development of carcinomata. There appears to be conflicting information, but their use is becoming widespread.Garyk Joseph
General Practitioner
Manly Vale, N.S.W.
Robin Marks, Professor of Dermatology, University
of Melbourne, comments:
Dr Joseph has raised an interesting point about the possible carcinogenic
effect of the use of topical tretinoin or alpha-hydroxy acid creams because
of the tendency to either irritate the skin, or else sensitise it to sunlight.
One of the problems with the use of tretinoin is that it sensitises the skin to sunlight and people will burn easily without adequate photoprotection. A history of sunburn in the past is one of the risk factors for skin cancer, both for melanoma and for non-melanoma skin cancers. Thus, it seems logical to query whether or not the use of tretinoin might enhance the risk of skin cancer.
The answer is that there is no evidence that it does so. On the contrary, tretinoin has been reported to be useful in reducing carcinogenic risk. It has been used topically to treat solar keratoses and thus prevent their progression. It has also been used systemically in chronic immunosuppressed patients to delay the development of squamous cell carcinoma in particular, but also basal cell carcinoma. There are no data available on either carcinogenic risk, or reduction of carcinogenesis, for alpha-hydroxy acid creams.
In summary, photoprotection is advised with the use of tretinoin or alpha-hydroxy acid creams. However, it is largely related to preventing the short-term effects of acute photosensitivity, rather than because of any established long-term risk of carcinogenesis.
Editor, – I refer to the article `Pneumonia in the Nineties' (Aust Prescr 1999;22:37-9). Is there any evidence from controlled trials (or other solid evidence) that the guidelines of the last 10 years have altered any outcome in community acquired pneumonia? What is the evidence that we should be substituting anything for amoxycillin routinely, even though many organisms associated with pathogenesis are not susceptible in vitro, if the clinical outcomes are similar?
Tom Perry
Physician
Department of Pharmacology and Therapeutics and Department of Medicine
University of British Columbia
Canada
Dr K. Christiansen, the author of the article, comments:
Dr Perry is quite correct in that there have not been any controlled trials comparing the outcome for community acquired pneumonia for the various therapeutic guidelines that have been formulated over the last 10 years. The most relevant publication is of the medical outcomes and antibiotic costs associated with the use of the American Thoracic Society (ATS) guidelines in 864 outpatients with community acquired pneumonia. The study found that 62% of patients less than 60 years of age with no co-morbidity received therapy consistent with the ATS guidelines. There was no significant difference in medical outcome between those with consistent and inconsistent treatment. The cost was however significantly less (3-fold lower) for those in whom the ATS guidelines were followed. For patients more than 60 years of age or with co-morbidity, the ATS guidelines were not well adhered to with only 18% of patients receiving therapy as recommended with more than 50% of patients receiving a macrolide or tetracycline only. Not only were the costs greatly reduced (10-fold lower) but the medical outcome was the same with a trend to higher mortality and subsequent hospitalisation in the ATS consistent group.
The comment made by the authors was that the outcome supports the recommendation for macrolides for young patients without co-morbidity, but that there is no apparent benefit for the more costly ATS recommended therapy in patients with co-morbidity or older age. No comparisons were made with amoxycillin therapy.
Reference
1. Gleason PP, Kapoor WN, Stone RA, Lave JR, Obrosky DS, Schulz R, et al. Medical outcomes and antimicrobial costs with the use of the American Thoracic Society guidelines for outpatients with community acquired pneumonia. JAMA 1997;278:32-9.
Editor, – In the excellent recent articles on pneumonia and the appropriate use of antibiotics (Aust Prescr 1999;22:26-8 and 37-9), I was a little surprised, as a radiologist, to see the degree or pattern on x-rays of the chest did not come into the decisions of which antibiotics to use. My training taught me that lobar pneumonia needed a different group of antibiotics. Is this not still the case? Also, the radiological distribution of several large patches and `more consolidation than illness of the patient', usually with a dry cough indicated mycoplasma.
Is the previously taught clinical maxim of `if discharges are clear, it is likely to be a virus and if the discharge is thick, such as white, yellow or green then antibiotics are of benefit' still relevant?
Bruce Markell
Radiologist
Newtown, N.S.W.
Dr K. Christiansen, the author of the article, comments:
Although there are typical clinical presentations for lower respiratory tract infection by Streptococcus pneumoniae and the `atypicals', Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella spp, there is much overlap and studies have shown that it is not possible to predict accurately the causative organism.1,2 Similarly, studies on the radiographical appearances 3,4,5 show that discrimination is not possible. More recently a direct comparison was made between chlamydial and pneumococcal pneumonia.6,7 An epidemic of Chlamydia pneumoniae occurred during a prospective study on community acquired pneumonia enabling the identification of 46 patients for whom a definite aetiology could be determined. This study confirmed that chlamydial pneumonia and pneumococcal pneumonia cannot be distinguished on clinical and radiographical grounds. Given that the causative agent cannot be predicted accurately by either clinical presentation or radiological appearance antibiotic therapy cannot be decided on these parameters.
References
1. Farr BM, Kaiser DL, Harrison BDW, Connolly CK. Prediction of microbial aetiology at admission to hospital for pneumonia from the presenting clinical features. Thorax 1989;44:1031-5.
2. Fang G, Fine M, Orloff J, Arisumi D, Yu VL, Kapoor W, et al. New and emerging etiologies for community acquired pneumonia with implications for therapy: A prospective multicenter study of 359 cases. Medicine 1990;69:307-16.
3. Tew J, Calenoff L, Berlin BS. Bacterial or nonbacterial pneumonia: accuracy of radiographic diagnosis. Radiology 1977;124:607-12.
4. MacFarlane JT, Miller AC, Roderick-Smith WH, Morris AH, Rose DH. Comparative radiographic features of community acquired Legionnaire's disease, pneumococcal pneumonia, mycoplasma pneumonia, and psittacosis. Thorax 1984;39:28-33.
5. Chan CH, Cohen M, Pang J. A prospective study of community acquired pneumonia in Hong Kong. Chest 1992;101:442-6.
6. Kauppinen MT, Saikku P, Kujala P, Herva E, Syrjala H. Clinical picture of community-acquired Chlamydia pneumoniae pneumonia requiring hospital treatment: a comparison between chlamydial and pneumococcal pneumonia. Thorax 1996;51:185-9.
7. Kauppinen MT, Lahde S, Syrjala H. Roentgenographic findings of pneumonia caused by Chlamydia pneumoniae. A comparison with streptococcus pneumonia. Arch Intern Med 1996;156:1851-6.
Editor, - In her paper `Pneumonia in the Nineties' (Aust Prescr 1999;22:37-9), Keryn Christiansen states that `penicillin was used for almost 4 decades before resistance was detected'. As a bright-eyed undergraduate in 1953, I can very clearly remember sitting in a cold lecture theatre at Sydney University enthralled by a stimulating young lecturer by the name of Ruthven Blackburn, who was trying to instil the fundamentals of medicine into what was most likely his initial class of dental students. I don't think I was alone in being impressed by the breadth, depth and detail of his knowledge as he recounted his experiences in the wards at nearby Royal Prince Alfred Hospital. Not only did Dr Blackburn present overwhelming evidence for the acquired resistance of certain strains of streptococci to penicillin, he successfully predicted that other nominated antibiotics would provoke the development of resistant organisms. He was later appointed to the chair of medicine at Sydney. If it has taken the rest of the world until the early 1980s to wake up to the phenomenon of antibiotic resistant organisms, then so be it. However, let us not overlook the visionary contribution made by this prescient academic and physician. By the same token, let us not blind ourselves to the possibility of future instances of mankind's failure to heed nature's warnings. What odds genetically engineered crops?
John Watson
Dentist
Bathurst, N.S.W.
Editor, - I have been following your articles on initiatives to improve antibiotic use (Aust Prescr 1999;22:26-8). I agree that the profession needs to be more discriminating in its application of antibiotics even though we all know this sometimes runs counter to the treatment expectations of individual patients. There has been much talk regarding the appropriateness of antibiotics for otitis media. As an otolaryngologist, most of the patients that filter through to me have been under-treated with respect to their ear infections rather than over-treated. The same might be said for rhinosinusitis. I suspect we may see a return to surgical means of treatment such as myringotomy. The laser-assisted myringotomy, as an outpatient procedure under local anaesthetic, certainly shows promise. Myringotomy may actually improve the outcome of middle ear infection and reduce the incidence of otitis media with effusion, which many people believe is a form of `antibioma'.
Whilst on the subject of antibiotic use and resistance, it has long concerned me that the indiscriminate use of common antibiotics in animal husbandry needs serious attention. Many organisms that have plagued mankind in the last 2000 years have apparently mutated from domestic and occasionally wild animals. High density farming practices with constant exposure to antibiotics in feedlots must surely be an excellent means of selecting resistant strains of bacteria just waiting to be transmitted into the human population. Can we be reassured that our efforts are being matched in animal husbandry? If not, I fear we are wasting our time.
David M. Merry
Otolaryngologist
South Hobart, Tas.
Editor, – In `Electronic prescribing' ('Letters' Aust Prescr 1999;22:28), G. Gabb and A. Vitry refer to `cheaper, but potentially biased, industry-subsidised electronic packages may change the dream of therapeutic Utopia into a nightmare'. This is certainly not the case for the package I purchased in 1993. It has transformed my prescribing to be more accurate, legible and an instant source of approved drug information. I have taught this package to many other doctors and we and others have shown that it is lauded by doctors, patients and pharmacists. When prescriptions are generated electronically the Government saves money because fewer adverse events result from drug-drug, drug-disease, drug-pregnancy and drug-sports interactions.
Peter Tribe
General Practitioner
Melbourne, Vic.
`Be not the first by whom new drugs are tried, Nor yet the last to lay the old aside'.
M.R. de Silva
General Practitioner
Glenbrook, N.S.W.
