CISSUS QUADRANGULARIS Side Effects & Safety. Some specific commercial products containing Cissus quadrangularis are POSSIBLY SAFE when taken by mouth appropriately short-term (for up to 6-8 weeks). These products can cause side effects such as headache, intestinal gas, dry mouth, diarrhea, and insomnia.ISSUS QUADRANGULARIS Side Effects & Safety. Some specific commercial products containing Cissus quadrangularis are POSSIBLY SAFE when taken by mouth appropriately short-term (for up to 6-8 weeks). These products can cause side effects such as headache, intestinal gas, dry mouth, diarrhea, and insomnia.