Delta-8 Temperature Cross-Tolerance Extended to Chlorpromazine but Not Every Tested Drug in Mice

A 1985 mouse study found temperature cross-tolerance involving delta-8 THC, its 11-hydroxy metabolite and chlorpromazine. The same cannabinoid histories did not produce the reported cross-tolerance to several other drugs.

Parent and metabolite adaptation differed in magnitude

Daily intravenous dosing rapidly produced tolerance to cooling from both cannabinoids. Cross-tolerance between them was reciprocal, with a larger tolerance magnitude for the metabolite. Similar direction did not establish identical dose-response behavior.

Cross-drug transfer was selective

The cannabinoid-tolerant conditions showed temperature cross-tolerance to chlorpromazine but not to morphine, pentobarbital or reserpine under the tested conditions. Those null comparisons limit a claim that the animals became generally resistant to any cooling drug.

A common endpoint does not identify one receptor

Reduced sensitivity across two compounds can suggest overlapping adaptation without proving identical primary targets. The study measured hypothermia, not every action of the comparator drugs. It also did not establish an interaction profile for people taking prescribed medication.

Applying the distinction

An interaction summary should retain both the positive chlorpromazine comparison and the drugs for which transfer was not reported. Removing the null comparisons would make adaptation look broader than this experiment supports. It should also retain the temperature endpoint, since cross-tolerance on cooling is not a result about every clinical action of those drugs.

What the finding means

The study contributes a defined positive comparison and several useful negatives. It does not justify changing medication doses or imply protection from sedation and impairment. Species, exposure direction, metabolite identity and the thermal endpoint must accompany the cross-tolerance claim.

For related interpretation, see interpreting cannabis tolerance claims.

Research reference

Yamamoto I; Watanabe K; Narimatsu S; Hamajima K; Yoshimura H (1985). Cross-tolerance to the hypothermic effect of delta 8-tetrahydrocannabinol 11-hydroxy-delta 8-tetrahydrocannabinol and chlorpromazine in the mouse. European journal of pharmacology. doi:10.1016/0014-2999(85)90752-6.

This discussion draws on the supplied study abstract.