Acetaminophen in aSAH to Inhibit Lipid Peroxidation and Cerebral Vasospasm

Aneurysmal subarachnoid hemorrhage (aSAH) is an often devastating form of stroke with high
morbidity and mortality despite advances in surgical management. Approximately 30,000
patients annually suffer aSAH in the U.S. For patients who survive the initial subarachnoid
hemorrhage, delayed cerebral vasospasm occurring from days 4-14 is the greatest cause of
neurological disability and death. A growing body of evidence incriminates
hemoprotein-catalyzed lipid peroxidation as the mediator of the vasospasm.

Hemoglobin released from lysed red cells in the subarachnoid space becomes oxidized, in which
state it acts as a pseudoperoxidase and generates the protein radicals that induce lipid
peroxidation. F2-isoprostanes formed by this lipid peroxidation are highly potent
constrictors of cerebral arterioles. We have demonstrated a more than 5 fold mean increase in
F2-isoprostanes in the cerebrospinal fluid of patients with aSAH; this increase is maximal at
the time of delayed vasospasm, and the level of increase is a function of the severity of the
aSAH. We hypothesize that such vasoconstrictors are major contributors to the vasospasm
produced by the hemoproteins, hemoglobin and myoglobin, in diseases in which they are
released from their cellular confines.

We have discovered that acetaminophen (APAP) is a potent inhibitor of hemoprotein-catalyzed
lipid peroxidation with an IC50 for hemoglobin of 15 uM, which is in the range of plasma
levels resulting from therapeutic doses of the drug in humans. Acetaminophen acts by reducing
the ferryl-oxo radical form of the heme, and thereby prevents formation of the hemoprotein
radical that initiates lipid peroxidation. To assess proof of concept in vivo, we determined
the effect of acetaminophen in a rat model of rhabdomyolysis in which renal failure results
from intense vasospasm. Acetaminophen blocked lipid peroxidation in this model, and prevented
the renal failure with a dose that produced plasma levels in the therapeutic range for
humans.

We also have demonstrated that N-acetylcysteine (NAC) will inhibit hemoprotein-catalyzed
lipid peroxidation. Moreover, NAC administration increases the levels of glutathione in vivo,
and glutathione is a co-substrate for the glutathione peroxidases that can reduce the levels
of peroxides in the environment of the aSAH . This is important as acetaminophen is most
potent in inhibiting hemoprotein-catalyzed lipid peroxidation when peroxide concentrations
are low. This concerted evidence is the basis for a hypothesis that NAC will augment the
efficacy of acetaminophen as an inhibitor of hemoprotein-catalyzed lipid peroxidation in
aSAH.

These finding provide the rationale for a pilot study seeking proof of the concept that
acetaminophen-based regimens can inhibit lipid peroxidation in patients with subarachnoid
hemorrhage. Lipid peroxidation will be determined by analysis of F2-isoprostanes in
cerebrospinal fluid. If such inhibition is seen, that then would provide a basis for a larger
multi-center investigation to assess the effect on clinical endpoints.

This pilot study will determine whether APAP, NAC, and APAP in combination with NAC will
inhibit lipid peroxidation in aneurysmal subarachnoid hemorrhage.

Inclusion Criteria:

- Ages ≥ 20

- Fisher Grade III or III + IV SAH based upon admitting CT scan

- Aneurysm secured by either clipping or coiling within 72 hours of SAH

- Intracranial aneurysm confirmed by angiography or CTA

- Presence of ventriculostomy for external ventricular drainage (EVD) prior to
randomization

Exclusion Criteria:

- Consent unobtainable

- Enrollment in another interventional study

- Patient is pregnant or lactating

- Known co-morbidities that could affect outcome of this study

- Contraindication to CTA

- Serum creatinine > 1.4

- Documented allergy to iodinated contrast that cannot be adequately treated with
premedication

- Documented allergy and/or intolerance to ApAP

- Baseline liver disease

- History of recent alcohol abuse with documented ALT or AST above normal laboratory
values

- Documented history of both malnutrition and decreased serum albumin below normal lab
values

- Documented abnormal platelet count below normal lab values

- Documented abnormal PT or PTT above normal lab values

- History or evidence of active asthma

- Documented allergy and/or intolerance to N-acetylcysteine

- Currently taking phenytoin, carbamazepine, or phenobarbital

- Currently taking isoniazid (INH, Lanzid, Nydrazid)

- Severe life-threatening complications resulting from standard aneurysm treatments that
will likely prevent completion of the study

- Patient unsuitable for the study, in the opinion of the investigator(s)