Interaction between isotretinoin and drugs used in an HIV-infected patient?/nA patient with an HIV-

Fråga: Interaction between isotretinoin and drugs used in an HIV-infected patient?

A patient with an HIV-infection is treated with antiviral agents such as zidovudine, lamivudine and indinavir. The patient is also presently treated with trimethoprim + sulfamethoxazole and earlier with acyclovir. Due to pronounced skin disorders he is also treated with prednisolone.

The questioner has recently read an article showing good results of isotretinoin in these patients. Is there a risk for an interaction with isotretinoin in this patient?

Sammanfattning: No documentation has been found in the literature of interaction between isotretinoin and the drugs used by this patient. However, since most of the HIV drugs are new on the market, the risk of an interaction cannot be excluded. The drug of special interest concerning interactions used by this patient is indinavir as it is metabolised to a high degree via cytochrom P450 (CYP3A4). However, in the present case the risk of an interaction seems low.

Svar: No information could be found in the literature of an interaction between isotretinoin and the above mentioned drugs.

Data on the metabolism of isotretinoin is limited. It is oxidized via cytochrome P450 in the liver to the metabolites 4-oxo-isotretinoin, tretinoin and 4-oxo-tretinoin (1).

Zidovudine is excreted by the kidneys in unchanged form (10 to 20 percent) and as glucuronide (50 to 80 percent) (2).

The excretion of lamivudine by the kidneys is almost complete (2). Trimethoprim and sulfamethoxazole are excreted by glomerular filtration; trimethoprim is also excreted by tubular secretion. Sulfamethoxazole is excreted partly in unchanged form but also as acetylated form up to 60 per cent and glucuronide up to 15 percent. Trimethoprim is excreted in active form up to 50 percent (2). Prednisolone is mainly metabolized in the liver by conjugation and hydroxylation by mixed function oxidases, and only 10 to 15 percent of the drug is excreted in the urine in an unchanged form (3). Acyclovir is mainly excreted unchanged via the kidney (4). Indinavir is metabolized by an inhibition of CYP3A4 and may thereby interact with several drugs (5). 1 Drugline nr 12490 (year 1996)

2 Drugline nr 13962 (year 1996)
3 Drugline nr 11957 (year 1995)
4 Drugline nr 10822 (year 1993)

5 SPC indinavir (via VLM Apoteksbolaget)