**6. Management**

The initial antimicrobial therapy should take into account four factors: (1) suspected organism (2) type of drug (3) the solvent used by the addict and (4) the location of Infection [17].

Empirical therapy in acute severely ill patients must consist of ampicillin and cloxacillin with gentamycin or vancomycin with gentamycin (in patients allergic to penicillin) [17]. *Staphylococcus aureus* must always be covered. Anti-pseudomonas agent must be added in a pentazocine drug addict. If an IVDA gives a history of brown heroin use mixed with lemon juice then an anti-fungal agent must be added due to a high risk of candida septicaemia. Anti-microbial therapy can be de-escalated once the specific causative organism is isolated on blood cultures.

Due to reluctance of IVDA for prolonged hospital admission and the concerns related to their discharge on intravenous antibiotic therapy, a few studies have studied the possibility of treating IE in these patients with short course antibiotic therapy [23].

A 2 week treatment regimen has been advocated in non-complicated isolated tricuspid valve endocarditis. These patients must have low risk features such as good response to therapy, methicillin sensitive *Staphylococcus aureus*, small vegetation size (less than 20 mm), no features of peripheral embolization, absence of metastatic infection, lack of involvement of left-sided valves or prosthetic valve and absence of a severely immunosuppressed state. In such cases, a short 2 week course of intravenous cloxacillin or oxacillin alone may be used [24]. These patients must be closely followed up and the response to therapy must be assessed.

In complicated cases a 4–6 week course of intravenous therapy must be utilised. These include situations where there is poor response to antibiotic therapy, large vegetation size (>20 mm), septic emboli, use of penicillinase non-resistant antibiotics, and a severely immunosuppressed state such as HIV with a CD4 count less than 200cell/ml and associated involvement of left-sided valves [25–27].

Due to a high rate of recurrent IE in IVDA, surgery should only be considered in the following situations: (1) intractable right-sided heart failure with poor response to diuretics; (2) persistent bacteraemia despite use of appropriate antimicrobial therapy; and (3) large vegetation size of greater than 20 mm that do not diminish in size after repeated episodes of pulmonary emboli [25, 28, 29].

In general the outcomes of patients with IVDA related IE have been poor post surgery. A substantially high long term mortality has been reported for IE related surgery in IVDA compared to non-drug users [30–32].

 In HIV-infected IVDAs with IE cardiac surgery does not worsen the outcome of either the IE or the HIV [17]. Patients with advanced HIV infection with severe immunosuppression. However, valve replacement surgery may have unacceptably high risks in selected patients with advanced HIV infection, low CD4 counts, and either a history of failed antiretroviral therapy or ongoing drug abuse that precludes therapy with antiretroviral agents [33].

The most commonly performed surgery for tricuspid valve endocarditis includes valvectomy, valve replacement or repair [34]. Valve repair is advocated by some studies but repair has not proven to be superior to either valve replacement or

valvectomy. In a few cases of RSIE valvectomy may be performed initially followed by subsequent bioprosthetic valve replacement once the infection has subsided and drug use discontinued. Pulmonary valve rarely requires replacement except in extreme cases of valve destruction. In cases where pulmonary valve replacement is deemed suitable, a homograft is preferred.
