Abstract
Chittaranjan Andrade, Professor, Department of Psychopharmacology, National Institute of Mental Health and Neurosciences, Bangalore, India:
Flupenthixol is a thioxanthene antipsychotic drug which has a 5-HT2/D2 receptor blockade ratio that lies in between that of conventional neuroleptics and atypical antipsychotic drugs [1]. This may explain why the drug is suggested to have stimulant and antidepressant properties, favourable for maintenance therapy in chronic schizophrenia. The depot form of the drug, flupenthixol decanoate (Fluanxol; Lundbeck, Bangalore, India), is often preferred in poorly compliant patients. It is administered by deep intramuscular injection to minimize the risk for injection site reactions as have been described with haloperidol decanoate [2, 3]. This report presents an instructive case of repeated injection site reactions to flupenthixol decanoate.
Mr A, an obese, 34-year-old patient with chronic schizophrenia, was procribed maintenance therapy with intramuscular flupenthixol decanoate in the dose of 20 mg once every 3 weeks. One month later, he returned with the request that his medication be changed because he had developed a subcutaneous abscess in each buttock on the two occasions that he had taken the injection. Each abscess had required incision and drainage.
The nurse who had administered the drug had both times injected it into the buttock. Despite the presence of a large deposit of gluteal fat, a disposable needle of conventional length (approximately 2.5 cm) had been used; probably, this had resulted in the drug being injected into subcutaneous tissue, leading to local irritation and hence the development of the abscess on each occasion.
A MEDLINE search using the keyword flupenthixol decanoate with injection reaction and adverse effects as the qualifiers failed to reveal any report of local abscesses developing with the depot preparation; the same qualifiers revealed several references for injection site reactions with haloperidol decanoate. Nevertheless, such reactions probably do occur with flupenthixol decanoate because the manufacturer's literature describes preventive precautions that need to be taken at the time of intramuscular injection.
Interestingly, this patient had received haloperidol decanoate in the buttocks each month for 2–3 years previously without having experienced any local reaction; yet, on both the occasions that he received flupenthixol decanoate he experienced a local reaction. This suggests that flupenthixol decanoate may have greater propensity to irritate subcutaneous adipose tissue than haloperidol decanoate.
Finally: unless a very long needle is used, obese patients should preferably receive depot neuroleptic preparations in the deltoid region, or anterolaterally into thigh muscle, rather than into the gluteal region, in order to minimize the risk of abscesses resulting from the injection of the drug into subcutaneous fat.