All these drugs change the way you feel in some way.

Heroin 

Heroin can reduce a person's desire for Sex and might mean they are less aware of staying safe during Sex. Injecting drugs of any kind with shared needles, syringes and other equipment carries a high risk of contracting a number of serious Infections / viruses, including HIV and Hepatitis C.

Cannabis

One of the effects of cannabis is to make people more relaxed. In a similar way to alcohol, this can mean people feel less inhibited and more sexual. Being aware of this and having Condoms ready can make it easier to practice Safer sex.

Stimulants

Drugs like speed and cocaine can make people more confident, chatty and outgoing. Ecstasy, especially, can lead to temporary feelings of loving everyone around you. At these times some people are more likely to want to have sex. Again, staying sexy and healthy can be made easier by being prepared. When using drugs, it is still possible to talk about and have the kind of sex you and your partner want.

Psychedelics

Drugs like LSD / acid and magic mushrooms temporarily alter the way people see the world and themselves. It may be that sex is the last thing they want, or it may mean that their sexual desires are heightened. The same advice about practising Safer sex applies.