Unemployed Christopher McGuire, 30, of no fixed abode, was arrested in London on Friday and Saturday night he was charged with one count of contamination of goods, and two counts of administering a noxious substance.
Christopher McGuire will appear at City of Westminster Magistrates Court on Monday.
Those four tampered packets were found in Bromley, Victoria and Beckenham in south London while another one was discovered in Northern Ireland.
Reckitt Benckiser, manufacturer of the drug, recalled the product on August 26 and halted distribution after discovering the boxes.
It estimated that 250,000 packets had not been returned.
Seroquel XL is a prescription-only anti-psychotic drug used to treat several disorders including schizophrenia, mania and bipolar depression.
People who accidentally take the drug may experience sleepiness and are advised not to drive or operate any tools or machinery until they know how the tablets have affected them.
Neurontin, used to treat epilepsy and long-lasting pain caused by damage to the nerves, can also result in drowsiness and lack of coordination.
Common side-effects of the prescription-only drugs, which may be seen in more than one person in 100, include pneumonia, depression, loss of vision, breathing difficulties and nausea.
Nurofen Plus is for pain relief and contains codeine. The affected packs all contain 32 tablets.
The large capsules of Seroquel XL 50mg tablets have gold and black packaging while Neurontin, which comes in a two-piece, white capsule, is stored in white and silver blister packs.
Nurofen Plus capsules have silver and black packaging.
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