Are there official or unofficial rules for drugs and addiction?

Question

I’m playing the 7ed version of Masks of Nyarlathotep. I decided to have my character a laudanum user as he’s an opium addict, because I was certain there were rules about narcotics and drug addiction in Call of Cthulhu.

But now I can’t find any in the main rulebooks (I have 5th to 7th edition), investigator and keeper handbooks, or other sourcebooks and campaigns I have.

Are there any official (or unofficial) rules for PCs using narcotics and for addiction? If there are, which book are they in?

The rules don’t have be official or for 7E (I’ll convert or adapt rules from earlier editions).

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For now, at the last session, myself and the GM decided to give my PC a penalty dice on skill and characteristic rules and movement, and to reduce the effects of Sanity rolls (sometimes he won’t make them, if he does the sanity costs might be reduced), when he’s under the influence of laudanum.

Answer 1

Berlin the Wicked City has a list of effects for various drugs, heroin included, on p40.

Heroin Duration: 1D3+1 hours. Effects: a bonus die is applied to all Sanity rolls. Insanity effects that would normally be suffered by an investigator are negated for the duration. Ignore requirement to make a CON roll to remain conscious when suffering a major wound. Immune to the knock-out blow maneuver (Call of Cthulhu Rulebook, page 125), and can be rendered unconscious only when reduced to zero hit points.

Side effects: nausea, constipation, and immobility for 1D3 hours. The investigator must attempt a Luck roll (or the person administering the drug makes a Medicine roll) each time heroin is injected; failure results in the loss of 2D6 hit points, while a fumble results in the same damage plus the permanent loss of 1D3–1 multiplied by 5 points of both CON and POW.

Addiction: an investigator is addicted after 1D3 uses, needing to take the drug once per day; failure to do so results in agitation, with all skills (except Cthulhu Mythos) suffering two penalty dice. If able to stay off heroin for 1D3+3 weeks, requiring a successful Extreme POW roll per week to do so, the penalty dice are removed.

That should cover most of your needs, and it's seventh edition so there is no need for conversion.