Quote from a standard dictionary of Biology.
"Cytochromes - located in the inner mitochondrial membranes"
Interestingly the proteins are light sensitive and a specialist demonstrated recently how his life as a General Practitioner changed when he noted that when a light was shone on the skin of the arm there were changes to the heart beat.
In the mitochondria minute electric currents are involved in the ATP/ADP energy cycle that controls respiration and therefore heart rate. Linked to that is the cyclic AMP that is necessary for hormone utilisation.
It has been admitted that chemicals such as the organophosphates can harm the mitichondria and that one of the results of the damage caused is a delay in the mechanism of the heart, among many other cardio-respiratory effects as reported by Ballantyne and Marrs. This combined with the known effects of chemicals and drugs on the cytochome P-450 which alone can increase susceptibility to pharmaceuticals by 40-fold may explain all of the dangerous reactions to treatments and such deadly problems as Cot Death, Adult Sudden Death Syndrome, Chronic Fatigue Syndrome and Multiple Chemical Sensitivity. A useful list of drugs and their effects in those with damaged mitochondria is to be found at www.MitoAction.org

I am a scientist with thirty years experience in Biochemistry and Molecular Genetics. My personal scientific interest is in the individual responses to the development of toxicity in response to biologically active molecules, including drugs. I have extensive experience working in drug and toxicology laboratories.

Pharmacogenetic studies relating to psychotropic drugs have generated a great deal of information

The main background points arising from this knowledge include the following:

• Despite increasing choices in medication management, many patients on psychotropic medication still experience poor outcomes related to inadequate medication response and significant adverse drug events, including neurotoxicity.

• Psychiatric medications may exhibit toxicity not only on the basis of their therapeutic use but also (and mainly) on the basis of their pharmacokinetic (what body doing to drugs) and pharmacodynamic properties (what dugs doing to body).

• Individual variations in drug pathways influence the responses of a patient to treatment with psychotropic drugs. Children, woman and adolescents with metabolic polymorphisms may be at greater risk for adverse drug events than individuals with normal metabolism (ability to eliminate toxins or drugs).

• Psychotropic drug prescribers should consider treatment-resistant patients as potential abnormal metabolisers. Nearly 80% of all drugs in use today, along with most psychotropics, are metabolised via testable metabolic pathways.

• Patients with psychiatric disease are at increased risk for being on multiple medications and complex regimens, which makes them particularly vulnerable to drug interactions, with the consequence of developing toxicity.

• Clinicians response to treatment resistance is to optimize dosing in their treatment of psychiatric symptoms. They may incorrectly conclude that the patient is just anxious or dramatic. However, in the abnormal metabolisers population, so called “somatic symptoms” associated with psychiatric diagnoses may in fact be medication intolerance exacerbated by dose titration.

Part 2
Adverse Drug Reaction manifestation (appearance):

Psychotropic medications have been associated with a variety of Adverse Drug Events (ADEs), including neurotoxicity development. Wall et al, 2010 (Mayo Clinic USA) created a list of Adverse Drug Reactions that have been linked to abnormal metabolism of psychotropics:

From Wall et al (2010)
ADVERSE EFFECTS ASSOCIATED WITH ABNORMAL METABOLISM 13-51 references:

Reduced metabolism (ie, poor):
Extrapyramidal Symptoms 14-22, Tardive dyskinesia14,34-36, Oversedation 38-40, Cardiovascular complications (ie, tachycardia, hypertension, hypotension) 46,47, Weight gain 46,47, Neuroleptic malignant syndrome 48-50, Serotonin syndrome 51, Suicidality 22,51

Increased metabolism (ie, ultrarapid): Opioid toxicity 23-33, Nausea 37, Paradoxical excitation 41, Treatment nonresponse 43-45, Suicidality 13

Individual responses to treatment:

The genes that code for the enzymes involved in the metabolism of drugs are highly polymorphic and appear to be highly variable between individuals. The most commonly studied cytochrome P450 (CYP) enzymes include 2D6, 2C19, and 2C9. Polymorphisms and gene duplications in these enzymes account for the most frequent variations in phase I metabolism of drugs since nearly 80% of all drugs in use today, along with most psychotropics are metabolized via these pathways.
According to our data published in Pharmacogenetics in 2009 patients with drug-induced akathisia have a high prevalence of the abnormal metabolisers genotype.
I believe that pharmacogenomic testing has a significant role in modern psychopharmacologic practice and that the accumulated knowledge has the potential to fill some of the scientific uncertainties in neurotoxicity interpretation.

Part 3
We need new approach in medicine development which allows us to:
- develop precise and clear recommendations for practitioners with an evaluation of benefits verses harm for different groups of antidepressants and psychotropic drugs
- to stop speculation in the media and in other publications about drug toxicity and promote the benefits of an individual approach to treatment
- to promote warnings about the different reactions that different people can have to antidepressants and psychotropics
- to avoid clinical malpractice lawsuits for hospitals and practitioners. Given that some pharmaceutical companies already provide this information, sooner or later such cases will be the subject of liability for medical practitioners.
- Medical practitioners, psychiatrists and caregivers should be involved in the treatment regime and should be aware of the signs of the development of the adverse drug reaction

As Dr Francis Collins said: It is predicted that within 10-20 years systems medicine will prevail in the form of P4 Medicine:
1. Predictive (from the genetic background information)
2. Personalised (individualised treatments)
3. Preventative (using the knowledge of the individual predisposition)
4. Participatory (patients/caregivers should participate in the treatment)
Participation of doctors, caregivers and patients in treatment should be part of the medical program and we already have the scientific and technical background to support this new development.

To Yola and Bruce UK,
You are both right, but you are talking about different levels: Bruce about ‘inside’ cells processes, Yola about ‘outside’ cells processes.
Inside cells: cytochrome enzymes are located on the inner mitochondrial and endoplasmic reticulum membranes.
Outside cells: gene expression differs in different tissues depending on the type of cytochrome and tissue type.
Cytochrome P450 is a very large complex of proteins, which located in all cells; however, they have different function in specific tissues.
We are talking here about Phase I liver detoxification system cytochromes.

Thanks to Yola and Irina for their expertise and scientific information on this complex subject.
However. I must ask if we can really look at the inner and outer systems in isolation.
The mitochondria take part in cell production and survival and therefore they influence the properties held within and by the cells they produce.
The various forms of RNA and DNA work together to reproduce themselves and make the very proteins and enzymes required for that process.
"Major enzyme complexes found in the inner mitochondrial membrane are synthesised part on mitochondrial ribosomes and part on cell sap ribosomes" - proteins are manufactured by cells on the ribosomes and the entire system is dependent on the energy produced by the mitochondria, which employ natural bonds with phosphates.
The enzymes are themselves proteins. The cytochromes are proteins. Many hormones are proteins and utilise cytochrome P-450 enzymes.
All must be in homeostasis and all chemicals disrupt that balance to various degrees.
Recent research suggests that cells can detect nutrients in food and that even this can influence hormones.
Drugs and chemicals that bind to the mitochondrial ribosomes and interfere with mitochondrial protein synthesis cause toxicity to mammals.
"endocrinology disorders, and exposure to toxins are among the many medical problems that can cause mental impairment, depression, anxiety, delusions, hallucinations, aggressiveness and a variety of other psychological symptoms and syndromes." - Abnormal Psychology 1995.
The drugs act on the same sites as the poisons and none of this knowledge is new. “The Biochemistry of the Nucleic Acids” was first published in 1981 and has sections on gene mutation and recombinant DNA technology.
Perhaps eliminating the poisons should be the first step to solving this problem?