The Effects of Valproic Acid on Zidovudine Glucuronidation and Pharmacokinetics in HIV-Infected Patients.

Preliminary studies using human liver tissue have shown that valproic acid inhibits the metabolic inactivation of zidovudine (AZT), which may prolong the plasma half-life of AZT and thus prolong the duration of the drug's effects in the body.

Six asymptomatic HIV-infected patients are treated with AZT orally every 8 hours on days 1 through 4, then with a single dose on day 5 (after 8 hours of fasting), followed by pharmacokinetic sampling. On days 6 through 9, patients receive AZT orally every 8 hours in combination with valproic acid (lowest dose in the first 5 patients and a higher dose in patients 6 and 7) orally every 8 hours. On day 10, AZT and 1 of the 2 doses of valproic acid are given orally as single doses, followed by pharmacokinetic sampling. AZT is continued alone orally every 8 hours on days 11 through 14, then resumed at the patient's usual dose beginning on day 15. Per 03/09/92 amendment, dosing schedule may be modified slightly to accommodate patients with scheduling conflicts.

Inclusion criteria

Concurrent Medication:

Allowed:

Vitamins if already being taken prior to start of therapy.

Patients must have:

• Asymptomatic HIV infection.
• CD4 count between 300 and 650.

Prior Medication:

Required:

• AZT at doses between 500 and 1200 mg/day for at least 6 weeks prior to enrollment.

Allowed:

• Aspirin, Tylenol, or ibuprofen up to 48 hours prior to start of therapy.

Exclusion criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Positive Hepatitis B surface antigen or clinical evidence of chronic active hepatitis of any type.
• Signs or symptoms of HIV infection including oral candidiasis, history of multidermatomal zoster, unexplained weight loss in excess of 10 percent body weight in the past 6 months, chronic diarrhea, or history of AIDS-defining opportunistic infections.

Concurrent Medication:

Excluded:

• Concomitant medications (other than AZT) for the 14 days prior to start of therapy.

Patients with the following prior conditions are excluded:

• History of AZT intolerance including hematologic, hepatic, and/or neurologic toxicity.
• History of seizures.
• History of any antiepileptics within the past 10 years.
• History of abnormal bleeding or intrinsic or extrinsic coagulopathy.
• Signs or symptoms of HIV infection including oral candidiasis, history of multidermatomal zoster, unexplained weight loss in excess of 10 percent body weight in the past 6 months, chronic diarrhea, or history of AIDS-defining opportunistic infections.

Prior Medication:

Excluded:

• Antiepileptics within the past 10 years.
• Prior valproic acid.
• Concomitant medications (other than AZT) within 14 days of enrollment.